H4Plugins finally released!

And finally...112 files of IOT goodness for ESP8266, ESP32 and (excepting WIFi) STM32-NUCLEO. It was designed to make it easy for you to write custom IOT apps running multiple simultaneous functions. It is currently running my own home. Go get it now - I hope you find it useful. https://github.com/philbowles/h4plugins

Some "upgrades" weren't published, they escaped. A week of woe.

I have just come through a programming problem so frustrating, so annoying, so intractable that not only has is it taken me well over a week of shouting at the screen and hair-pulling, but also the only way to recover is the catharsis of sharing my nightmare…and a very stiff drink.

There are many lessons to be learned herein: it’s going to long, it will be very detailed and all-too-recently painful, but I think it will be worth it if you can hang on in there.

Executive summary: code and library versions can be important (and sometimes harmful!) …and “latest” is not always “best”

That nightmare started shortly after I released version 3.1 of Esparto… a couple of folk noticed problems. One in particular was using the much-more up-to-date 2.5.0 core of Arduino ESP8266 whereas all my testing, development and release had been with 2.4.2…

I felt churlish telling him it wasn’t supported, sorry -  since I am the one behind the times and really should be up-to-date myself, I always advise others to do so! I therefore set up my “upstairs” machine with Arduino IDE 1.8.8 and ESP8266 core 2.5.0. to try to a) verify the problem and b) work out a fix. 

That's when the “fun” began. Sure enough, the problem he described was happening exactly the same to me “upstairs” while all was fine downstairs…before I continue, a touch of background is necessary:

Esparto relies fundamentally on the ESPAsyncWebServer library which in turn relies upon the same author’s ESPAsyncTCP library. For good measure (well, Amazon Echo uPNP discovery, actually) is also uses ESPAsyncUDP. Note the common thread: “async”. Any / all / every piece of serious code on the ESP8266 needs to be async...or it’s just a toy, but that’s a whole other book. Back to my upstairs machine: unloved and unused for many a moon, it lacked those essential libraries, so I installed them, automatically getting the latest version – of course. The stage is now set for Act I of the tragedy.

More background: Esparto has the fancy “real-time” GPIO lights on its web UI, comme ca:

These were controlled using websockets (as was the whole of the web user interface [web UI]) and after much similar recent wrestling, had led me to insert a ton of code to limit or “throttle” the amount / rate of websocket messages going to the web UI. For example when a very “busy” GPIO might be changing state hundreds of times a second, neither the ESP8266, nor any browser, nor indeed your eyes can keep up with that so it makes sense to limit it, as failing to do so has fairly rapid and disastrous consequences, namely the ESP8266 runs out of free heap and crashes.

Lesson 1 is that if there is one key technique behind successful ESP8266 programming, it is heap management. And being async! Two. Two main techniques. But heap management it absolutely vital since the ESP8266 has so little and some libraries are very cavalier about how they use it. At core 2.3.0 I couldn’t compile the whole of Esparto since the core libraries didn’t leave enough free heap! In the early days, I also experienced “random” crashes which took me a long time to put down to sudden massive heap exhaustion (6k / 8k / 10k within seconds etc) within the ESPAsyncWebServer library, with a) no warning and b) no way to check ahead of time when the “danger zone” was imminent…

 A quick bit of “long story short” here which has ironic repercussions to follow later. About 9 months ago, I “had words” with the developer, even going as far as to provide a graph showing the exact problem once I’d spent literally weeks tracking it down…in essence there was no internal check before queuing a websocket write – neither that there was sufficient heap nor whether a large queue was building because they were coming in faster than they could be despatched…hence when either / both those things occurred* the internal queue grew out of control and used all the heap, crashing the system.

* = over 19x per second. Yep, a massive 19. Any more and the free heap drops like a rock, irrecoverably. So three pins doing 6 transitions each (e.g. flashing on/off 3x per sec) is fine. Add a fourth, and make it change more than 1x per second and you are in a terminal one-way nose dive.

The complete lack of any way to detect / prevent this led to my fairly strong words with the developer.  I ended up doing a whole ton of work to calculate this magic number, then another whole ton of work to “throttle” the GPIO and/or any other control signals to /from the webUI. Anyway, that all worked. So I carried on and released it.

Back upstairs, I am wondering how the hell only ever 8 items get added to the “run” tab dropdown box. Wiresharking the conversation, I can see I’m actually only sending 8 even though the code calls the sending function 22 times. Coincidentally I’m only sending 8 GPIO updates too even though dozens are physically occurring. Very suspicious. Another “long story short” because it actually only took me an hour or so to find the problem and my jaw dropped open in horror when I did.

The websocket lib (with which I was far too familiar due to the problems above) has changed quite a lot. At the point of socket write it effectively says

 if messageQueue.length() < MAX_QUEUE_LENGTH, add message to queue. 

That’s it. No error code if it doesn’t get queued. No fall-back and requeue. No warning message, not even at debug level! No way to discover, let alone change the hard-coded value of MAX_QUEUE_LENGTH which is…you guessed it: 8. Nope, anything more than 8 outstanding requests just get silently ignored and thrown away. I rushed to the author's webpage – no mention WHATSOEVER of any of this in the documentation. Now what goddamn use is that to man or beast?

A caveat before I continue. Those libraries are close to works of art, and I had (note past tense) nothing but admiration and respect for the author (who does a ton of other seriously clever stuff too) and Esparto couldn’t work without them. Thus it not only pains me, but I actually find it quite difficult to come out and say just quite how shitty this “fix” is. I put it down to either a) the author having had a seriously bad night on the beer before “fixing” it or b) handing it off to a far, far, inferior programmer to “do a quick fix”. It is honestly so out of character, I simply don’t understand it. It stands out like a sore thumb compared with the rest of his highly impressive code.

Irrespective, it renders that implementation of aync websockets almost totally useless for any practical purposes. 19 per sec was pretty shabby already: knocking it back to a carved-in-stone silently-discarding 8 is unforgivable. Honestly, if the author had asked me to come up with a fix myself which must be the worst possible solution on every front, I doubt if I could have managed anything so appallingly slack-arsed as what now in there. If I were paying someone as a programmer and they wiped this off their shoe, they’d now be serving coffee at Starbucks. But it doesn’t run out of heap anymore. It is the equivalent of fixing your car’s brake problems by removing the distributor cap.

So...

After the swearing had stopped (I’m lying, I still sometimes swear at the insult of it, and we are two weeks on…). I remembered that Machiavelli said we must live in the world the way it is, not the way it should be: I needed another solution, and fast.

The Solution, Part 1: Out with the old

Websockets are bi-directional and I used them to react to UI events such as clicking a button to reboot, or change tabs etc, so immediately that all had to change. To be honest the JavaScript code was a bit “lace-curtain” so I smiled through gritted teeth as I was forced to tidy it all up and make classic “ajax” calls instead. Of course, I then had to re-jig a lot of the webserver handling. While I’m doing so, I may as well do the JSON part properly…

Everything JSON I looked at was massively top-heavy, so I wrote my own JSON encoder to handle a few specific cases of sending JSON data back to the UI from std::vectors / std::maps which is how a lot of it is internally held.

After the first few days then, with an almost totally new 600-lines of ajax-compatible JavaScript , completely reworked webserver functionality, websockets ripped out root and branch and a custom JSON encoder written…phew…I was ready to stitch in the “push” side of the bidirectionality, the little-known “Server-Sent Events” or SSE. Luckily, it is already included in the ESPAsyncWebServer library. I just prayed some ******* idiot hadn’t “throttled” it to a hardcoded 8-at-a-time like they’d done to the websockets! A brief look at the code showed it appeared thankfully unfettered in that respect. Oh how much too soon I smiled…

First, the elephant in the room. Why had I been working with such an old library? Simply because there is no easy way to find out it had changed. But 9months+??? Don’t shout yet, yes I know a lot of Arduino libraries come up on that bloody annoying “some of your boards…” popup when you start the Arduino IDE…the libs I’m talking about aren’t included. Why not, you will have to ask the author. Technically, I know the reason: their metadata doesn’t match exactly the format that Arduino uses to identify libraries when it trawls github. Exactly why not, you will have to ask the author. Yes, I know that’s the second time I said it. I’m not happy with him right now. And you’re probably only just over halfway through the “fun”. I had consulted the docs dozens of times in that 9 months. Nothing on the site to show a new release available. Docs unchanged, even to the trained eye. Why would I think it needed updating? At best it would have just shifted this problem back 7-8months.

Ironically (remember that far back) when you look at what changed…much of it was obviously as a result of my graph…As the Chinese say: “Be careful what you wish for”.

The Solution, Part 2: In with the new

Very new. I’d never heard of SSE before, so a bit of reading and experimentation was needed. In reasonably short order, I had a prototype working. The basic concept was there, now to the leg-work of replacing all the “push” stuff which was mostly the GPIO pretty flashing lights, but due to heap constraints, several of the “live” tabs have to be “fed” asynchronously and piecemeal too.

Again I’m smiling through gritted teeth because I am forced unwillingly to make my code a lot better and more robust. At last, I am able to implement the “persistence of vision” optimisation that allows me to “throttle” the GPIO light to a rate that is just slightly faster than the human eye can detect…no point throwing 100 events per sec (if the interface can handle it*) at the webUi of you can only spot the difference in 24 “frames” per sec, like a movie. 

Actually it’s 23.80 – doing some simple maths will explain why – all Esparto timing is in milliseconds…and all ESPArto “maths” uses integer arithmetic. Floating point bloats the bin incredibly and it overkill for a couple of small calculations. Giving a “delay” to a timer requires telling it how many milliseconds to wait. For example, 500mS makes it run 2x per second (1000/500). Q: What it is 1000/24 ? A: 41.6666 if using floating-point, which I’m not, so it’s actually 41 from a truncated integer divide. Now 1000/41 = 24.39 per second, slightly more than I need and - if I accept that 23.809523 is close enough – which I do, then the divisor becomes 42. I need say no more. On with the show.

The plan is that when someone is viewing the UI, I will “scan” all GPIOs @ 24ish times per second and send a list of any that have changed to the JavaScript that flips them red/green. Obviously, I don’t want that overhead if no-one is watching so I have to be able to turn on off the “cinema projector” when the theatre is empty, and restart it instantly as soon as another customer arrives.

Also, I wanted – at last – to overcome the cheap’n’cheesy limit that has long existed on only one web viewer. Slight trick with that is that different tabs open for different viewers need different “live view” push data as well as the GPIO/ MQTT status etc that all active viewers need. Similarly any "watching" the same tab e.g. the graphs all need to sse the graphs updte at the same time. Managing that required a fair deal of extra code and rewrite to the webUI. Since I was having to “gut” the whole code body, I thought I may as well take this chance to get it good once and for all. All I finally need then is an easy way to detect incoming and outgoing clients.

Ah.

With a websocket you get “onConnect” and “onDisconnect” events, which make it easy. SSE is one-way only "push" technology. It doesn’t really care or stop working if it is “shouting at an empty room” so while obviously you get a “connect” message; if the client dies or goes away, you never get a "disconnect". In fact, you don't get told at all.

This is a serious pain, but not fatal, on the JS side, the EventSource reconnects automatically after a user-configurable “timeout” and provides the messageID of the last message received, so you can tell the difference between a new client (who needs the whole page) and an existing reconnect who just needs continued live push data to whatever “tab” he’s on. With some hoop-jumping and a home-brewed clientID handshake / special HTTP header in the Ajax request / configurable periodic keep-alive “ping” – I can keep track of who’s connected …and close down the hot-running cine projector when all the clients timeout (strictly, after – on average – 1.5x the “ping” time…but anyway…)

Phew. A lot of rework, and a whole new technology, but a better “product” results.

Until that is, you realise two things:

1: Haunting echoes: “…throwing 100 events per sec (if the interface can handle it*)”. Asterisk = It can’t. To be fair, it can handle a helluva lot more than 8 at a time! Due to the way I now incorporate all changed GPIOs into a single “frame” it copes reasonably well with the chosen 24ish fps. So If I have five or six pins all changing quite rapidly that’s the equivalent of – say – 120 GPIO events / sec, shifting the bottleneck now to the JS in the browser which usually can’t cope that fast…but hey: the eye can’t tell. Also, anything throwing in hundreds per sec is still only going to get sampled @ 24fps so while it may be a way removed from the physical truth, again your eye can’t tell. At least we don’t get sudden huge heap losses. Until…

2: This:

Those downward spikes? The 4kB+ sudden "you-ain’t-go-it-no-more" bites out of the free heap that happen when the client side automatically reconnects. Since there is no “on disconnect” or equivalent, it takes some time of throwing 24fps at the library before it realises the client has gone and breaks the connection. In the meanwhile, it queues up the requests into a rapidly-growing heap-chomping MCU-crashing shitstorm just like... just like those old websockets. Talk about frying pan and fire! 

A week down the line and all I have is the same problem in a whole ton of new untested code – but it’s worse, again there is no way to predict when it will occur. Nor is there any way that the library can / will tell you.

It happens when the underlying network code decides to break the connection, i.e. it’s a) too low down in the “stack” of code for me to even want to go there b) probably beyond my knowledge c) it really is pretty random. Upstairs it dies it every couple of seconds, down here it can go two minutes or more without a blink. Only two things mitigate it: 1) it is usually* less than the chunk the websockets used to grab. 2) The EventSource technology auto-reconnects “for free” – so if you can stay alive through the big chunk – albeit with a dead UI – then it pings back pretty quickly once the connection is remade. It takes 3 -5 seconds for that to happen though so the user experience is really choppy / stuttery / horrible.

*usually. It is usually 4kish but can be up to 10k in a couple of chunks and you can’t prevent it from conflicting with another request e.g. an Alexa command or a 2^nd viewer using a REST call…either of which will take it further down the hill to never-land on a one-way journey to the power-recycle switch. Something has to be done.

A quick dive into the code shows that it has no checking, no low/ heap prevention – ironically it is just exactly as bad the old websocket code before the “fix”, but not yet quite as bad as the new. This time, I have to prevent the same (very low) quality of “fix” taking out my final chance if I notify the author and he “fixes” it up the same way.

I need another solution. The only thing that can be detected is a sudden loss of about 4kb heap in a very distinctive pattern. If  only I can spot that from MY side of the fence and then hit the “pause” button on the cine projector until at least most of it has come back up once the auto reconnect is complete…I might be back in business.

You are going to think my solution was a bad choice and now – more than a week later – so do I. At the time it seemed like an easy option(!): I built a” heap heuristics” module deep into the scheduler which did a variety of measurements at very high speed behind the scenes…instantaneous loss between calls, rolling average loss (cyclical buffer over last N <configurable> calls) percentage difference from a) last call b) rolling average…ultimately I ended up with 2^nd differential i.e. difference between last two differences to try to narrow down the “acceleration” of the sudden 45 degree downward slope. Hmmm, really?

I spent days trying to work out where best to put the code, as the actual values vary greatly depending on where in the call stack it sits…etc. Should it run on all jobs (with a view to preventing other future problems) or just the GPIO "NetFlix" job? Even if its just on NetFlix, do I need to keep a portion running to keep the overall rolling average accurate...or do I just use the NetFlix rolling average? Is the "granularity" of last 10 measurements enough to "see" the nose-dive in time? Will I need more or will only 5 do it?  And what of the trigger values? Even though they will (of course) be configurable - I know already they wont be the same at the next version! 

The number of concurrent viewers change the trigger values. Bad network connectivity changes them. More pins change them. Every ***ing thing changes them- to the point where I could just about catch the node-dive about ¼ way down the slope, with many false positives but – fatally – the occasional false negative, i.e. a missed - and potentially fatal -“trough”. So even ofr all the configurability and complexity, it still wasn't working.

Despite the odds, I persevered through four or five days getting ever more frustrated and dispirited trying every permutation of placement, parameters, method, technique – each variant requiring major rework…I wsa paraying a certain combination would hit a "sweet spot" where I could "predict" every imminent nosedive. All the time I’m swearing and shouting “why can’t I just see the "$!%!"£$%^ing !"£$%^  message Queue length?????????????” 

Because if I could, I'd be able to see when it starts getting longer than X and immediately "back off" sending! Simples!

Not quite, because there is no way to pause to let it “drain” since the only reason it starts to accelerate in the first place is because the underlying network has already broken the link, so nothing will ever “consume” the queue contents. It took me a few days before that crushing realisation hit me. All I can do is wait until the library spots the network problem and then discards the whole queue in one fell swoop, giving that sharp upward recovery seen on the graph, which takes 3-5 seconds. During whihc time- of course - the UI is "frozen". I'm sent stuttering back to square one.

But wait…when the library does notice the network problem and “chops” the queue…as mentioned earlier, the JS notices pretty quickly and reconnects automatically. If I set that reconnection time very low (1/2 sec say) and find a way to make the lib do that cleanup sooner, by -DING! Spark of genius alert! – simply arbitrarily force-closing the connection, even while it’s still “good”…

It might all be a bit “dirty” crashing and reopening the connection all the time, but it will work. After all, upstairs with the weaker signal it is already naturally doing it a lot anyway. All I’m doing is giving nature a gentle early nudge! All I need is to get the queue length from the lib. Sounds easy.

I had been avoiding relying on someone else’s code and goodwill to accept my “fix” – but it’s the only way. How do I know? Because I put in a quite easy fix requiring only about 2 small changes and a new 6 or 7 line routine called getAvgMQL: “get average Message Queue Length”. A slight wrinkle is that the AsyncEventSource has up to n clients and it is the client that has the message Queue, so I have to average all the clients to get an overall figure. By experimentation, a queue length of 15 seems a good balance between “choppiness” and a harbinger of impending doom. Look at the following screenshot: running constantly for over 7 hrs now with a lot of pin activity and a maximum “reconnect trough” of about 2.5k That is the longest it’s been up for about 10 days.

The vertical bars are added when I do the forced close. As you can see, a couple coincide with what might be the start of a "trough". Some don’t: they are either just natural “busyness” or plain and simple false positives. Since forcing a close has very little overall effect on the smoothness, and is actually now part of the "normal" mechanism, "Frankly, my dear, I don't give a damn!"

What I do care is that the behaviour is – at last – predictable and controllable as well as being a reasonably good user experience for quite a heavy load:

Esparto.flashPattern("   ... --- ...",250,LED4);
Esparto.flashPWM(1400,10,LED5);
Esparto.flashLED(500,LED6);

D4 is toggling at a rate of 125mS or 8x per second. D8(LED4) is flashing S-O-S in morse code, i.e. … --- … on a timebase of 250ms i.e. each dot / dash is about 1/2 - 1/4 sec long sec on a continuous loop. D7(LED5) is a 10% duty cycle blip in 1.4sec period and D6 (LED6) is a simple 2x per second “square wave” so when the “peaks” line up, you are getting 12 transitions per sec from 4 different pins and the UI appears pretty responsive. Being honest, it can’t quite “do” the three short Morse blips, but now that it is stable and predictable, I can try upping the frame rate as well as well as tweaking down the Q threshold to get the optimum result.

With hindsight, If I had chosen the ”investigate / reverse engineer / fix / update” someone else’s highly complex library” route first, I’d have saved myself well over a week and a lot of hair.

Lesson 2: Don’t shy away from tough decisions if - in the long run – they are the best.

Lesson 3: Check your library versions regularly even if there is no sign they may have changed!

Lesson 4: Not all “upgrades” are good ones. For example, core 2.5.0 adds over 30k to the bin file for Esparto. Thirty K!!! It wouldn’t be so bad, but Esparto is pretty big already – in core 2.4.2 its about 430k so 2.5.0 puts that up to 450k…kinda right on the limit of what can be OTA’d into a 1MB device with the minimum SPIFFS for the webUI… Worse there is less free heap to start with, and what brought us here? Correct: low heap management - 2.5.0 just makes it worse. Right now , for me 2.5.0 is a huge retrograde step – and if that weren’t bad enough, there’s a real killer:

Esparto will simply not serve up its web page in 2.5.0 – its like it is running in glue / treacle. The exact same line-for-line code that works (now!) perfectly under 2.4.2 cannot get to first base and – for now – I’m all done with fixing other peoples’ bad upgrades. I’ll have to find a way around it a some point.

On the plus side: The web code is much more robust, and more easily expandabel if / when new features come along. The same is true of the core code and a few quite useful new features have been added:

"repeatWhile" function. Repeat function f1 every n mSec while f2 returns true and call f3after f2 returns zero to stop the repeat. This is perfect for “worker” threads “chunking up” a job in the background to conserve heap. F1 repeatedly performs a “chunk”, adjusting a counter / pointer F2 return the counter / pointer while its non-zero (still work to do) f1 keeps repeating and once all the data has been done, f3 can clean up / reset counters for next time etc. All of this is “interleaved” with other tasks, minimising heap loss and streamlining overall throughput.

Its what my "netFlix" function uses, and yes, I did call it that:

	
if(!netFlix){		
    Serial.printf("Start strobing @ %d (=%d.%dfps)\n",CII(ESPARTO_FRAME_RATE),1000/CII(ESPARTO_FRAME_RATE),((1000%CII(ESPARTO_FRAME_RATE)*100)/CII(ESPARTO_FRAME_RATE)));
    netFlix=repeatWhile([](){ return tab::nViewers(); },CII(ESPARTO_FRAME_RATE),
		[](){
		    vector<string> cp;
		    ESPARTO_CFG_MAP cPin;
		    int n=0;
		    for(int i=0;i<ESPARTO_MAX_PIN;i++){
			if(_spPins[i].dirty) cp.push_back(_light(i));					
			_spPins[i].dirty=false;				
		    }
		    if(cp.size()) _spoolBcast(jNamedArray("gpio",cp));
		},
		[](){ netFlix=0;Serial.printf("LAST PICTURE SHOW\n"); }
    ,ESPARTO_SRC_WEB,"flix");
}

While there are any UI viewers, repeat the "send changed pin" @ ESPARTO_FRAME_RATE. Oncce all viewers have gone, reset initial conditions so next viewer restarts.

Very simple but incredibly useful is vBar. It simply draws a vertical bar of a given color (default = red) across all graphs asynchronously, i.e. when you want it to happen, to show when a particular event has occurred, in context. I could not have fixed this problem without it!

Thrown in are web basic auth and the ability to change MQTT parameters through the UI and Amazon Echo v3 compatibility among several others minor changes.

Esparto v3.2 will be (code-wise) very different from v3.1 (almost a re-write!) even though it will look almost 90% the same! It will be out as soon as I’ve had a day off and got some of the new documentation(yuk) fixed up and new example code written.

Esparto v2.0 finally released!

Yes, it's "out of the door" at last. After some final "stress" testing and the creation / testing of 32 (yes, thirty-two) example programs, v2.0 finally goes public.

Intervening health problems added 8 months to the date(!) but at last I can now relax somewhat- with a well-earned beer.

Get Esparto v2.0  here at github 

Esparto V2 almost ready! The new web UI part 6

The lower panel(s)

Run

This is literally where the action happens. Esparto is designed so that commands can come from several sources:

• MQTT topics
• the web UI
• from within the app itself using the "invoke" functio

The first is one of the most common forms of communications between IOT "things" in home automation. You obviously need access to an MQTT "broker" (fancy name for "server", really) either your own or public one. At this very moment, there is no way to enter a username and password - except manually in your own code - so until I get that fixed... your own broker is the best bet. I use mosquitto (which can be found Mosquitto.org download page) on a raspberry Pi.

But don't despair if none of those options are available, you can still do a lot with Esparto through its own UI, or from your own code. Want to change GPIO0 (D3)'s debounce value for example? Either call Esparto.invoke("cmd/pin/cfg/0/15"); or come to this screen, select the cfg option form the dropdown menu, add the /0 to the Topic line and type 15 into the payload field. Then hit "Simulate MQTT" - Esparto's internals that actually "do the business" are called with exactly the same message as they would have received from a genuine MQTT server. Simples.

As commands are received and actioned (from any source) the stats are dynamically updated. Soon - and certainly before release - I shall add "Alexa" as a source because Esparto is fully Alexa-compatible by pretending to be a Belkin WeMo when asked in the right way. All it can do is "turn on "<your device> or "turn off" the same. That's as much as a lot of devices do, anyway.

The "all" source is special one built in to Esparto allowing you to send a single command to all Esparto device on your 'net, as well as addressing each one indvidually by its device name. For example - while not necessarily advised - "all/cmd/reboot" will do exactly what you think it would.

Users can to subscribe to any topic they choose - including # wildcards - when called back in onMQTTConnect (see previous post in the series for a simple example).

In the demo, the user has subscribed to a wildcard topic like so:

  Esparto.subscribe("wild/#",[](vector<string> vs){ 
        string suit=vs.front();
        Serial.printf("Wilcard handler suit is , card is %s\n",(CSTR(suit)),CSTR(vs.back()));
        if(suit=="hearts" || suit=="clubs" || suit=="diamonds" || suit=="spades"){
          Serial.printf("You chose the %s of %s\n",CSTR(vs.back()),CSTR(suit));
        }
        else Serial.printf("Invalid suit %s\n",CSTR(suit));
    },"cards"); 

(They also included  (not shown) a simpler topic "flash" which they wrote to call the same code as Alexa commands call. So when Alexa is told to "turn on testbed" it has the same effect as MQTT command "testbed/flash/1" for on  and ...0 for off. )

He/she has chosen to only allow this wildcard topic from another made-up source "cards"  so "testbed/wild/party" won't work, but" cards/wild/animal "will.

And therein lies a slight oddity - and a caution. Esparto cannot predict the billions of permutations that come after ...wild/ - only the user can decide that. Hence for the system to work Esparto not only has to accept anything of that form, it also has to add it to the above table and count it and that has consequences.

The user code in the demo rejects any subtopic except (rather suitably) hearts, clubs, diamonds and spades and would like the payload to be a card from 2 to 10 or J K Q A. Lazily, it doesn't actually validate the payload, but then all it does is parrot ack to you what you send it, so no harm done in this contrived case. In the real world such appalling coding (I should know, I wrote it - deliberately to bring out these points of course) will almost certainly lead to a crash if unexpected, unvalidated input and/or gibberish is fed to any wildcard topic - so be careful. Trust no-one, and validate everything to within an inch of its short life.

Another consequence is that the more wild rubbish you send that Esparto is duty-bound to accept, the longer that list will get, the slower the UI will become until finally Esparto's self-protection mechanisms will cut in and reject  everything from all sources until some memory is freed somehow. This will certainly cause erratic behaviour and possible meltdown at the nuclear power plant, so don't do it. If no memory can get freed, then your Esparto app will die a slow lingering death till you want to reboot it. When you do, remember it's your fault, not Esparto's. 

While this a shorter section than some others, this pane is probably one of the most useful of Esparto's many features. There is neither the space nor the time to go into detail about each of the commands and new ones are being thought of as I type...

You may find that all the ...dump... options are missing from the final release, as they are 90% used in debugging. It will be done in such a way that even average programmers will be able to hack into the code and just turn on a #define and recompile. They do steal heap though, whic is already in short supply so don't say you haven't been warned. On the other hand if I can trim some fat from elsewhere during my final code tidy, I might leave some/all of them in. Invoke("cmd/watch/this/space"), you might say.

Others are just fun to play with: .../pin/flash/... , .../pin/pwm/...  and  .../pin/pattern for example/...

Download the release when it's out "soon", edit in your own SSID/password/device name and give all the topics/commands a try - it's what Esparto is for.  Or wait 3 minutes for it to give up and go into AP mode then configure it with your phone.

And enjoy it!

Esparto V2 almost ready! The new web UI part 5

The lower panel(s)

Config

Now we start to see the real power of Esparto coming out. It has a configuration system where name/value pairs are automatically saved to SPIFFS (the ESP8266 Flash file system) as soon as they change and persist into the next reboot, i.e become permanent. Well, until the next factory reset, at least.

The demo code has a Latching push button on GPIO0 (Arduino digital pin D3) and a very "noisy" and sensitive  sound sensor (i.e. a high number of thousand IOs per second at the slightest cough) on GPIO12 (D6). It also configures the BUILTIN_LED for output. On a Wemos D1 mini that the demo was built on, this is on GPIO2 (D4). The hardware setup looks like this:

void setupHardware(){

  Esparto.Output(BUILTIN_LED,LOW,HIGH); // start with LED OFF                   

  Esparto.Latching(PUSHBUTTON,INPUT,10,buttonPress); // 10ms of debouncing

  Esparto.Raw(D6,INPUT,[](int s){ Serial.println("Do nothing"); });

  Esparto.throttlePin(D6,19);

}

I trust your first taste of the "esparto Way" wasn't too shocking or difficult? setupHardware() is equivalent to the standard Arduino-style setup() and you do the same kind of thing here as you would there - almost. You just do it Esparto-stylee - so for instance, no WiFi.begin and delay loops* Esparto is already connecting to your SSID "in the background" to speed things up.

Also you won't see pinMode calls: Esparto knows what mode to set automatically from the type of Esparto SmartPin you define. So really all we have is one line per I/O device, and often that's all you will need. The only "odd" or "tricky" thing is the throttlePin call. We'll get to the strange syntax in a minute, but first, what exactly is "throttling" and why do we need it here?

It is described in great detail in part 3 of this series, so if you want to know more read up on that first, but for now a simple one liner is that the sound sensors fires far more data than any tiny device can easily cope with -Esparto being no exception - so we have to slow it down, or "throttle" it. D6 is our noisy pin, so we tell Esparto only to allow through 19 of the thousands of 1s and 0s per second.

The reason this is such a low figure is explained in the earlier article. Your LED will still flash vaguely in time with your bangin' house or lounge jazz tracks...ish. Now to that weird syntax...

C++ Lambda functions:

See what? If you don't know about these already, ask Mr Google about them because you will quickly come to love them as much as I do. They are particularly good for callbacks and a lot of your code needs to be in callbacks so now is a good time to learn how to use them. If you are already frightened, fear not: you don't have to use them, the old-fashioned way still works. I will show you what that would look like in a moment and I'm sure you will soon be seeing the benefits of the new-fangled way.

What we want is for Esparto to tell us when pin D6 changes and what is has just changed to: a 0 or a 1. So we need to give Esparto a function that returns nothing (void) and takes a single int parameter, which holds the new state when the pin changed. Ordinarily we'd write:

void namedFunction(int s){

Serial.println("Do nothing");

}

and then our old-fashioned way would be:

Esparto.Raw(D6,INPUT,namedFunction);

But:

• It's more typing
• We have to invent a name for our free-standing "normal" function that doesn't do a whole lot
• namedFunction can live anywhere in your code base. If your code is large and you are anything like me, it can sometimes take a while to find, by which time you forgot where it was called from!

Let's break down the "new" way (it isn't new at all, it's been around since at least 2011)

,[](int s){ Serial.println("Do nothing"); }

[] = this is a lambda function - it has no name

(int s) = same as before, it takes an int parameter called s

{ Serial.println("Do nothing"); } = this is what the function does, its body. any valid C++ code can live inside the body including if/else blocks, other lambdas etc.

Not too painful, I trust? In summary it's a function with no name (an "anonymous function") that is "bolted in" to the place that needs to call it, instead of having to live outside on its own. It has many benefits:

• Less typing
• Less names to remember
• Lives alongside the thing that defined it and needs it: makes code more easy to understand and saves time hunting
• You can do things with it that you would never have dreamt of, like pass it, lock stock and barrel as an object to another function that can then call it on your behalf! That is beyond the scope of this post, though. Ask Mr Google.

I mention these in some detail because a lot of the example code uses them, for all the reasons above, and because I love them. Esparto could not have been written without them. I hope you come to love them too, and soon - they make working with Esparto a breeze and they're not really that tough are they? Welcome to the 21st century!

Why do nothing?

The demo is purely to show the raw LED beating closely-ish in time with either some music, clapping of hands, whistling, dogs howling etc. Since Esparto does all the checking for changes and SmartPins underneath does all the flashing automatically, there is nothing else for our demo code to do. This shows how powerful Esparto is. Ordinarily the lambda is where you would put your special code that makes your app different from the rest. I do exactly that with the Latching button, which starts and stops the LED flashing by calling buttonPress which you haven't seen yet, but is here in all its glory:

void buttonPress(bool hilo){

  if(!hilo) {

    uint32_t rate=Esparto.getConfigInt("blinkrate");

    Esparto.flashLED(rate); 

  }

  else  Esparto.stopLED();

}

User-defined config variables:

And in Esparto.getConfigInt("blinkrate"); you now see the Esparto magic starting to happen. I challenge you to look at the screen shot above and guess what happens when you change the value. Go on, have a go!

If you said "I bet the LED starts flashing at the new rate automatically", you're obviously catching on but you'd be wrong. Only because I'm teasing and you haven't yet pressed the pushbutton to start it flashing at the old rate in the first place. If you had already done that then yes, exactly correct: the LED instantly starts flashing at the new rate, well done! It's now no great leap of faith to correctly assume that changing the debounce value will, er, change the debounce value of the Latching button. You are getting a whole lot of functionality for free here.

But there's more: next time you reboot, the value will be brought back - the config system saves the value whenever it changes, you have nothing further to do. The BWF parameter just made up, to play with, does nothing, isn't used anywhere and you can type what you want in there just for the fun of seeing it survive a reboot. If you want real magic, read the next section on the run panel...

Yet more: send the command testbed/flash with a payload of 1 to start and 0 to stop from an MQTT client and guess what - correct the same thing happens as if you had pressed the button physically yourself. The code to make that happen? Here:

void onMqttConnect(void){

  Serial.printf("T=%d USER SAYS MQTT CONNECTED\n",millis());

  Esparto.subscribe("flash",[](vector<string> vs){ 

    Serial.printf("Doing my thing with %s\n",CSTR(vs.back()));

    buttonPress(!atoi(CSTR(vs.back())));

    });

}

Dont worry about the "vector" stuff, that's more C++ magic that is going to make your relationship with Esparto a much more fruitful one and will be covered in the future. For now be happy that you have just avoided 3 months of tearing your hair out and a learning curve like the side of a cliff, while getting an already pretty capable system "for free" from a mere handful of lines of code!

System config variables:

Anything starting with a "~" is a system variable which Esparto relies on to function properly. So:

1. never use "~" in your own config names
2. while you can put whatever you like in your own variables as long as your code knows what it means, the same cannot be said for system variables
3. never change a system variable unless you know what you are doing, and why!

Some system variables are easy to understand and make sense for the user to change. The ones I have chosen to expose for the demo are like that. By the time the full release comes round there will be a lot more, and they won't be as nice. I can safely predict that even when you read the "advanced guide" with a full explanation of what each does, you still won't want / dare / understand how to change them, so - just don't. Ever!

~fb2Ap: 

Is the millisecond count for the amount of time to wait for the WiFi to fail to connect before "falling back" to AP mode and offering yourself up to a phone, tablet etc to get in and configure a valid set of WiFi credentials. The demo has 3 minutes = 180,000 microseconds = 180 seconds. You may want less or more: feel free to change it to a sensible value that works for you.

~lh:

Is used to log the value of the heap every second to an MQTT broker, just in case the 3-minute graphs on the system page aren't enough. 1= start, 0= stop. It will publish /testbed/heap with a payload of the value once per second until you stop it, either by changing the value back to 0, publishing testbed/cmd/logheap/0 over MQTT or reading on to the next section on the run panel...

~mqXXX:

Unsurprisingly, the IP address, port and retry failure re-connection interval of your MQTT broker. Some day soon I will add ~mixer and ~mqPass to enable you to connect to an authenticating remote server. Some day...

Don't ask me about (or mess with!) the as-yet-unseen ~jitter variable - it's the plus / minus entropy timing spread adjustment factor to minimise asynchronous collision probability in the autoStats derived timer reset function. It is currently set to 10. Still fancy seeing what happens if you change it to 11? Or 243? No, I hoped not.

*Ever. No delay loops ever. They are bad, they break asynchronous libraries, stop other tasks from running and are generally BAD STYLE. Do not ever use one in an Esparto callback (or at all, in fact) you simply don't need to. If you think you do, trust me, you are wrong. There is always a better way. call Esparto.once(<x mSec delay>, functionToRunSoon); for example. Don't ever call delay(). Need I say it again?

Esparto V2 almost ready! The new web UI part 4

The lower panel(s)

Info

This is mostly self-explanatory but also raises a few points that are well worth knowing if you intend to become an "Esparto Expert".

These are all static values at the heart of the system, some of them permanently, some for example the IP address for this boot of the system only. They cannot be directly changed by the user. For some that can, see the next section.

Hardware Type:

This lets you know what's running "under the hood". It can be any one of these:

• ESP-01 (but why would you bother when there’s…)
• ESP-01S
• Wemos D1
• Wemos D1 mini
• Wemos D1 lite (and thus probably any other ESP8285 device)
• Wemos D1 pro
• NodeMCU 0.9
• SONOFF Basic
• SONOFF S20
• SONOFF SV

Esparto has been tested on all of the above. It will probably run on anything with an ESP-12 in it, but obviously I can't test every single device on the market/ If you want to send me one to try it out and modify if necessary...

I will be very interested to hear of anybody getting it running on any other platform e.g. NodeMCU 1.0 will probably work, as will (I expect) other SONOFFs

Unique Hardware ID:

This is the last 6 digits of the MAC address and is commonly used in new-out-of-the-box scenarios as a default name before choosing your own and setting your SSID / Password credentials the default name of the demo device would be ESPARTO-17D383. See part 2 earlier for more detail on this value and advice renaming your device to replace it.

IP Address:

Need I say more?

Flash Memory Size:

Same as above, except the answer is "Yes". 

Esparto weighs in at  over 410k - it has a lot of functionality and features. To support OTA updating (and who wouldn't want that?) a "sketch" (app) has to be able to fit into half the available flash size. On smaller devices e.g. the SONOFFs you get 1MB thus 512k is usable if you want OTA (and you do!).

As you can see things are already starting to squeak, so you need to keep your own additional code
small, efficient and light-weight. There is also a very limited amount of heap left. Esparto starts up with about 27k free, and that can go up and down rapidly - see the graphs in part 3 of this series for an example. Keep your heap use to a minimum and guard any heap-using routines with a check in what's free first if you want to avoid crashing (again, you do!).

The good news is that Esparto does so much for you that your own code will be small and consist mostly of short callback routines that Esparto will execute at the relevant time on your behalf. There is no loop() function and no setup() function. You will rapidly get used to doing things the "Esparto Way" once you see how easy it is.

H4 library version number:

If you want to get further than a simple "Blinky" it helps to understand the structure of Esparto. It is built from 3 main libraries, H4, SmartPins and Esparto itself.

H4 which handles all the timer functions, scheduling, task separation and "slip streaming" of asynchronous functions into the synchronous task queue which runs on the main loop. No more WDT resets, no more "volatile"s. When your task runs, it is (almost) the only player in town and the H4 library makes sure you have to try really really hard to break things or upset other tasks.

It comes with 7 of its own examples demonstrating how each and all of its functions work. Esparto "encapsulates" H4, so all of the H4 functions will appear to you as identical Esparto functions, so you do need to understand these first.

SmartPins library version number:

See above. Note the version shown is incorrect - by the time of  release it will also be 2.0.0 (actually it is, but I forgot to update the version number field before the demo - my bad!)

SmartPins as its name suggests manages all the input and output pins for you. It is what enables Esparto to give you the fancy real-time flashing LED display for all the pins. It also does everything you could ever want to do with a pin, including debouncing, interrupt handling (although there are good reasons why you would probably never need to use it), rotary decoding and much more.

The Encoder input type lets you manage a rotary with a single line of code - you tell it the name of a variable, and whenever you access the variable it will automagically have the current decoder value in it. One line of code! It's my favourite Esparto feature: most of my own mini-apps have some kind of "tweak" factor using a rotary, it's so easy. Some even have two...at the extra expense of one more line of code...I'll stop now, I think you have got the point.

SmartPins comes with nineteen sample program covering every in and out (literally!) of the many types of input modes it supports. It also has access to all H4's functions and relies on it 100% to function. Pretty much every example has at least one or two H4 features though of course they appear seamlessly as identical SmartPins features.

It is important then to work through the examples in order to fully understand the power and flexibility of Esparto, because in the same way, all Esparto functions are automatically the same as all SmartPins functions.

Even seasoned programmers will benefit, as Esparto works in a very different way from 99.235% of all the thousands of sample sketches you will find online. You need to learn the "Esparto Way", but for those with experience it won't take long at all.

Just as an example, here's the code (with comments removed for brevity) for the simple blinky. "Simple" includes having a fully debounced on/off switch unlike 99.476% of other blinkies.

NOTE: 

While H4 and SmartPins both have visible setup() and loop() functions, Esparto does not. There are two reasons for keeping them in:

1. To make the early examples more readily recognisable and ease you in to the "Esparto Way" and "chunk up" the amount of learning at each stage into bite-sized pieces.
2. To enable you to use them on their own without the full Esparto, although I can't think of any reason why you would want to unless you are the kind that likes to make things deliberately hard for themselves

#include <SmartPins.h>

SmartPins smartPins;

void buttonPress(bool hilo){

  if(!hilo) smartPins.flashLED(250);

  else smartPins.stopLED();

}

void setup(){

  Serial.begin(74880);

  Serial.println("LED will change state (flashing/off) on each separate button up/down press");

  smartPins.Output(BUILTIN_LED);

  smartPins.Latching(0,INPUT,15,buttonPress); // GPIO 0 + 15ms of debouncing

}

void loop(){

  smartPins.loop();

}

I hope you will agree both that it's pretty easy and also that you get "a lot for your money" for very little coding effort. That principle underlies the whole of the "Esparto Way": Esparto does 90% of the "heavy lifting", you plug in the remaining 10% which is specific to your IOT / home automation app. Esparto allows you to concentrate on just the code that's important to you - all the hard stuff "just works"

NBoot & Code:

These may be the first indication of a (hopefully very rare) problem. NBoot is the number of times this device has been rebooted and "Code" is the reason why. If it has just been freshly programmed then (as has the demo device) then it will read ESPARTO_BOOT_UNCONTROLLED.

What this means is that it was not shut down by user action, but forcibly rebooted, as the IDE does. You will also see this code if the device crashes for any reason.

If you click the Reboot button,. the code will become  ESPARTO_BOOT_UI. If you send an MQTT command e.g. testbed/cmd/reboot the code becomes ESPARTO_BOOT_MQTT and son on, although obviously you will replace "testbed" with your own device name first.

If you see an increased boot count and a reason you don't expect - something has gone wrong!

The "tXXX" values:

These measure the amount of milliseconds since boot up when:

tHW: 

The time after which your sensors, buttons, relays, remote controlled Gatling guns etc become ready to run. One of the fundamental design goals of Esparto is that your hardware should operate a) as early as possible b) whether you have a WiFi connection or not c) all the time, always.

Even if - as happens in the real world - bugs occur and the occasional crash occurs, your hardware will be back up ready to go in about 125 milliseconds. Impressive, non? It's one of the reason behind why Esparto won't let you play with setup() and loop(): it has quite a bit of complex setup of its own to do, and it has to happen fast, and in a very specific order.

tWiFi:

The time after which you can load up the web UI because your device now has a valid IP address.

tMQTT: 

Similarly, the time after which Esparto is actively listening for MQTT commands, both its own any any that you choose also to listen for. All Esparto command start with "cmd", so you must not use this in any of your own topics, or who knows when that Gatling gun may go off in error?

High values of either tWiFi or tMQTT may be early indications of problems with your router, network or MQTT broker. Or they may just be a sign of a slow network - only you will know. Personally, I'd worry about anything much more than the demo values. Again, I think 3.2 secs from power on to receiving MQTT commands is "in the zone".

Esparto v2.0 - sneak preview: Inside

"A picture is worth..." as they say:

The following 21 lines (one of which is a comment...) are all you need to turn a Sonoff Basic, S20 or SV into an MQTT device with a web interface...etc etc as described in the previous post "...outside". If you don't want diagnostics, you can lose the Serial,begin and cut another line.

The Sonoffs have a push button on GPIO0 and a mains relay on GPIO12. That's all they have, hardware-wise

#include <ESPArto.h>
// ToiioT-Etage is my SSID, pw="" (I live in the forest) my raspi mosquitto is on 192.168.1.4
ESPArto Esparto("ToiioT-Etage", "", "esparto666", "192.168.1.4", 1883); 
void buttonPressed(bool hilo){
  if(hilo) toggleRelay();
}
void mqttSwitch(String topic,String payload){
  toggleRelay();
  Esparto.publish("state",digitalRead(12) ? "ON":"OFF");
}

void setupHardware(){
   Serial.begin(74880);
   Esparto.Debounced(0,INPUT,15,buttonPressed); // 15 = ms debounce time
   pinMode(12,OUTPUT); // relay / switch
}
void onMqttConnect(){
  Esparto.subscribe("switch",mqttSwitch);
}
void toggleRelay(){
  digitalWrite(12,!digitalRead(12));
}

And the code above is all they need, and I ask you: "What could be simpler?"

True, you will have to physically FLASH upgrade it first time with a FTDI adapter, but after that, Esparto will update itself automatically as needed. It will appear on your WiFi network as esparto666.local and respond to an MQTT "switch" command, by toggling the power relay and will reply with an MQTT "state" message with a payload of "ON" or OFF". It will reconnect after any network failure and all the while, the manual button will still turn it on an off.

Plus it's inside your own network. No snazzy (but often rubbish) App to download. No security problems. No worrying if XYZ corp go out of business and close their cloud, that your lights will never work again...If you can use a web browser, you can control it. If you have an MQTT server, you can control it in much more detail. If you have a NODE-RED server, you can start to do really clever things with your whole house.

Let's look inti the code in more detail (shouldn't take long)

It doesn't look much like a typical Arduino sketch. There is no setup() function and no loop function. Esparto takes care of both, to make sure things are done in the "right" order and to prevent your code from accidentally breaking things or stopping it working.

Your code is all driven asynchronously by Esparto using callbacks. If you don't know what that means, you need to read the sidebar articles under "Essential Information". It starts with setupHardware. This is where you do what you'd normally do in setup. Having said that, much of what you'd "normally do" isn't needed any more.

Esparto.Debounced(0,INPUT,15,buttonPressed);

Tells Esparto that you want the button on GPIO0 debounced (for 15ms) and to call buttonPressed when someone pushes it or lets it go - i.e. when it changes. When it goes HIGH (the button on a Sonoff is "reversed" in sense: it goes LOW when you press it and HIGH when released) the relay is set to the opposite of what it is now. If its already on, it goes off etc - and that is the same as the standard firmware that it comes with when you buy it.

When Esparto has established a valid MQTT connection it calls onMqttConnect. Here, your code tells Esparto you want to receive "switch" topic message and when it gets one, it will call your code in mqttSwitch. As for a button press, you call toggleRelay which then publishes the current switch state to MQTT.

"And that's that"...as they also say.

Adding sensors to a "homebrew" board and adding lots of functionality on top of this is going to get more complex of course, but Esparto is designed to take a lot of the hard work out of that process too. It has a lot of "Hooks" where you can add callbacks in exactly the places you need to create a new "layer" of your own HA system on top of Esparto. That's how my own Chez Toi ioT system works: 90% of the code in each device is Esparto. Esparto has 9 different types of input pin it can manage for you, including rotary encoders and each of those only require one or two lines of code.

As an example my truc firmware when I fisrt wrote it was about 1200 lines of (pretty hairy) code and a lot of bugs. Now it handles GPIO on every pin of a WemosD1 and runs temperature PIR, sound, light, button and touch sensors. It also controls 433MHz RF switches, and it auto-updates itself. It's far more robust, easier to control and has two web pages (one of which is a live GPIO view) when the old one had only one very basic config page. Using Esparto, its only about 300 lines long and most of those 300 lines are a lot simpler and a lot more obvious to read.

But the biggest "gift" it brings is this: it runs all your code on the main loop thread, in a non-overlapping "job queue". All asynchronous events are "serialised" into the queue so no more problems of resource clashes, hangups, WDT resets and a hundred other headaches. It also provides tools for you to do the same from your own code. Each task runs separately in turn and can't interfere with/break/stop any other task, unless you deliberately make it do so. Again, if you don't know what all that means, read the "Essential Information" but what it translates to is: It prevents you from accidentally falling into about 90% of the common traps that newcomers fall into - and not all of them are obvious even to some experts. Some of them confuse experienced programmers for days and make grown men weep. Kiss 'em all goodbye.

It's fair to say that some of the complexity that Esparto hides (by deliberate design) would easily put off a lot of beginners, so having "MQTT in a box" is a huge help to getting started in the world of Home Automation and IOT. Now its absolutely true that if you can write a simple sketch to flash an LED you can also write one to produce your own Sonoff firmware. How's that sound for starters?

Of course Sonoff aren't the only player in town: that exact same sketch above will compile and run on Wemos D1, NodeMCU and (with a touch of "fettling" and shifting pin 12 to e.g. GPIO2) even an ESP-01 or ESP-01S.

Esparto is the result of 2years' worth of  thousands of mistakes, false starts, burned fingers, frustration and swearing - so that you don't have to go through it all again yourself.

Dont' Delay!

The following code looks like it will wait until pin 5 goes LOW until allowing the loop function to run:

void setup(){

  Serial.begin(74880);

  pinMode(5,INPUT_PULLUP);

  Serial.printf("T=%d Waiting\n",millis());

  while(digitalRead(5)==HIGH);

  Serial.printf("T=%d Ready\n",millis());

}

The while loop is a technique used on other systems - and probably works - but here's what happens on an ESP8266:

T=5204 Waiting

Soft WDT reset

ctx: cont
sp: 3ffef240 end: 3ffef420 offset: 01b0

>>>stack>>>
3ffef3f0:  3fffdad0 00000000 3ffee3c8 40201c28
3ffef400:  feefeffe feefeffe 3ffee3ec 4020237c
3ffef410:  feefeffe feefeffe 3ffee400 40100718
<<<stack<<<

It just crashed. What happened was, your code is in a very tight loop, and while it is there, the WiFi code cannot run. The "watchdog timer" thinks the processor has "hung up" and so it restarts the system. This alone is one good reason is why programming the ESP8266 is different from programming e.g. an AVR with the Arduino IDE. If you replace the while statement with:

  while(digitalRead(5)==HIGH) delay(1); 

Then it works as you would have expected. The system sits doing nothing until pin 5 goes LOW. So it looks like "delay" is the solution. Before we added it your code was "doing nothing" - and it crashed. It doesn't take a rocket scientist to deduce then that delay cannot also be "doing nothing" therefore it must be doing something!

That something is allowing the WiFi code to run in the background, hence the WDT isn't worried.

Oddly, delay(0) would also have worked. As would the special function yield() which does pretty much the same as delay(0). delay is specifically designed to "yield" the CPU, i.e. "let go" of it for a short while, and in that short while, the WiFi code can use it.

"But Wait!" I hear you cry: "I haven't done anything with WiFi! I haven't even tried to connect to it!" - and that's true. But - look at the crash information: "T=5204" The system had been running for 5.2 seconds before it even got to the while loop. Did Serial.begin and pinMode really take 5 seconds?

If not, then what was the CPU doing for 5 seconds?

To answer that, I'd like to to actually try this experiment: don't just read it and take my word, actually do it. First - and this is vital: if you use a brand new chip or one you have used for "messing about with WiFi" then the following code might not work, You have to use a chip that you have already successfully connected to your WiFi, at least once before. When you have that, load the following sketch:

#include<ESP8266WiFi.h>

#define CSTR(x) x.c_str()
#define TXTIP(x) CSTR(x.toString())

WiFiEventHandler    gotIpEventHandler,disconnectedEventHandler;
              
void wifiEvent(WiFiEvent_t event) {
    switch(event) {
        case WIFI_EVENT_STAMODE_CONNECTED:
            Serial.printf("T=%d WiFi Connected SSID=%s\n",millis(),CSTR(WiFi.SSID()));
            break;
        case WIFI_EVENT_STAMODE_GOT_IP:
            Serial.printf("T=%d WiFi got IP %s\n",millis(),CSTR(WiFi.localIP().toString()));
            break;
        case WIFI_EVENT_STAMODE_DISCONNECTED:
            Serial.printf("T=%d WiFi lost connection\n",millis());
            break;        
        default:
            break;
    }
}

void wifiDisconnectHandler(const WiFiEventStationModeDisconnected& event){
  Serial.printf("T=%d Disconnected (reason=%d)\n",millis(),event.reason);
}

void wifiGotIPHandler(const WiFiEventStationModeGotIP& event){
  Serial.printf("T=%d Connected to %s (%s) as %s (ch: %d) hostname=%s\n",millis(),CSTR(WiFi.SSID()),TXTIP(WiFi.gatewayIP()),TXTIP(WiFi.localIP()),WiFi.channel(),CSTR(WiFi.hostname()));
}

void setup(){
  Serial.begin(74880);
  delay(1000);
  Serial.printf("T=%d Setup\n",millis());
  WiFi.onEvent(wifiEvent);
  gotIpEventHandler = WiFi.onStationModeGotIP(wifiGotIPHandler);
  disconnectedEventHandler = WiFi.onStationModeDisconnected(wifiDisconnectHandler);
  }

void loop(){
  Serial.printf("T=%d LOOP: Do something\n",millis());
  delay(30000);
}

Now then, this is where it starts to look like a magic trick: Your WiFi SSID and password are not in that sketch and there is of course, nothing up my sleeve - I do not and could not possibly know them. Even if I did, there is no WiFi.begin anywhere in the sketch that would tell the ESP8266 to connect to your WiFi. But it will connect. Go on, if you don't believe me, try it. Surprised? I hope so. Note also that the connection occured after the loop had started running - certainly on my chip it did:

⸮T=6303 Setup
T=6303 LOOP: Do something
T=8126 WiFi got IP 192.168.1.113
T=8126 Connected to LaPique (192.168.1.1) as 192.168.1.113 (ch: 6) hostname=ESP_836EDC
T=36303 LOOP: Do something

What have we learned?

1. The ESP8266 remembers the last successful WiFi connection and automatically re-connects to it - without you even asking!
2. It can take quite a few seconds to connect.
3. The ESP8266 is doing a lot of things "in the background" even when you think that nothing else is happening except your code.

That last one is the one you need to think very hard about. When "your" code crashes - it might not actually be your code causing the crash, it can often be your code causing some other code to crash, which can make it hard to pin down the true cause. The whole purpose of this article is to predict that - in a large percentage of cases - there will be a delay call just before the crash, so, for my next trick:

Insert a delay(1) before the Serial.printf in wifiGotIPHandler like so:

void wifiGotIPHandler(const WiFiEventStationModeGotIP& event){
  delay(1);
  Serial.printf("T=%d Connected to %s (%s) as %s (ch: %d) hostname=%s\n",millis(),CSTR(WiFi.SSID()),TXTIP(WiFi.gatewayIP()),TXTIP(WiFi.localIP()),WiFi.channel(),CSTR(WiFi.hostname()));
}

Here's what happens on mine:

T=6302 Setup
T=6302 LOOP: Do something
T=8124 WiFi got IP 192.168.1.113
T=8124 Connected to LaPique (192.168.1.1) as 192.168.1.113 (ch: 6) hostname=ESP_836EDC

Exception (9):
epc1=0x401050b9 epc2=0x00000000 epc3=0x00000000 excvaddr=0xffffffff depc=0x00000000

ctx: sys 
sp: 3ffffdb0 end: 3fffffb0 offset: 01a0

So now what have we learned?

1. That time travel is apparently possible: the delay(1) before the Serial.printf caused the crash (trust me, it did) yet the Serial.printf still worked! Welcome to the wonderful world of asynchronous programming...
2. That as little as a 1ms delay can cause a crash? No,we have learned that...
3. delay is not - after all - such a wonderful solution: when used in the "wrong" place it is a nightmare.

I see a lot of code in example sketches, in question from "newbies" that is littered with delay calls, often with values that you just know have been made up on the spot, because there is often no need for delay to be there at all. A lot of people think it's the answer to a variety of problems, but I'm here to tell them - and you - that it's the indiscriminate use of it that is the cause of many.

delay can only be called - without problems - from the "main loop thread". If you call it from the "background thread", you've seen what happens. Some callbacks (especially timers) and all interrupt service routines (ISRs) do not run - by definition - on the main loop thread, so calling delay inside them will cause problems.

We are now in a "catch-22": The best way to write code for the ESP8266 is the event-driven style, but the same method makes other code break. The solution however, is easy: don't use that "other code". Don't use delay. If you need something to happen at a later date, use a Ticker, or the author's H4 library (which adds a lot of functionality to the Ticker class) github.com/philbowles/h4

Many of the ESP8266 libraries use callbacks. If you know - in every case - whether or not it's safe to call delay in the callback, feel free to ignore everything here. But if you don't, don't. Since you can't really do anything much more productive without those libraries other than flashing LEDs, the best starting point is:

D O   N O T   C A L L   D E L A Y

Unless, of course you understand all of this already and know exactly what you are doing.

Event-driven programming with callbacks

The previous article (which you should read now, before you continue) how "callbacks" made programming the ESP8266 easier and less error-prone - but what do they look like and how do they work?

Let's take the case where you want to read a sensor every minute. I've seen a lot of code like this around (or variations of it)

#define SENSOR 5

void setup(){
  Serial.begin(74880);
  pinMode(SENSOR,INPUT);

}

void loop(){
  if (millis()%60000){
    Serial.println("do something");
  }
}

Looks OK? Often the if(millis()... will be taking the current time, subtracting the previous value and checking if it == 1000 which of course requires a global variable for the previous value and some extra code, but the principle is the same - and it doesn't work!

loop() gets called about 40,000 times a second. So you are likely to "do something" up to 40 times because the value of millis() will be the same until another millisecond elapses! So, depending on how long "do something" takes, depends on how often it will be called, which is nothing like what you think you were doing, and if "do something" relies on accurate timing, your program will not work.

"Easy!" you think, "I'll set another global variable while doing something, then check it in loop and make sure I only do something once per loop".

"or, I can put delay(60000) inside the loop and then my timing will be accurate!"

The first option adds more code, more complexity (none of which is necessary and usually frowned upon - for plenty of good reasons - by experienced programmers) and the second just won't work.

No, the solution is to use the Ticker library which runs a highly accurate timer and calls back your code when the timer expires:

#include<Ticker.h>
#define SENSOR 5

Ticker  everyMinute; 

void doSomething(){                        // this is your callback function
  Serial.println("do something");
}

void setup(){
  Serial.begin(74880);
  pinMode(SENSOR,INPUT);
  everyMinute.attach_ms(60000,doSomething); // "register" your callback
}

void loop(){
}

The most important thing to realise here is that doSomething does not get called by everyMinute.attach_ms(60000,doSomething) in setup...all you are doing here is telling the Ticker library the name of your function - "registering" it - which will then be called every minute.

In a nutshell, that's how callbacks work. They are lot simpler, a lot cleaner and prevent you from re-inventing the wheel every time you write a sketch. But the most important  thing, is that they "just work" and they avoid numerous common problems.

Imagine if you had three or four sensors which need reading at different times...the loop code would very soon start to get complicated...using Ticker, you just have three or four tickers going off at different times, each with its own separate (obvious) callback which does just what that sensor needs. It's a lot more obvious and easier to read as well as being a lot less error-prone.

If you use "lambda" functions (and if you don't, you should - google them now) it's  even easier:

#include<Ticker.h>
#define SENSOR 5

Ticker  everyMinute;  

void setup(){
  Serial.begin(74880);
  pinMode(SENSOR,INPUT);
  everyMinute.attach_ms(60000,[](){ Serial.println("do something"); });
}

void loop(){
}

The "callback" is defined "inline" with the thing that will call it and saves having a separately defined function.

The Ticker library also allows you to pass a single (32-bit) parameter to your callback function, which is extremely useful and solves a lot of additional issues in the majority of cases. If however you want to pass two parameters, or call a class method when the timer "fires" - you are in for a lot of "fun" - unless you look at the author's "H4" library github.com/philbowles/h4 which is specifically designed to do just those things. It also adds more creative timer functions, such as calling back at random times or calling back a fixed number of times. Finally, it allows you to "chain" functions, i.e. call one after another has just finished. This allows some quite complex sequences to be built in to your code very simply indeed.

If the H4 library is used correctly, you will never need to call delay()...nor will ever need to know (far less need to muck about with) the "watchdog timer" and if you don't yet know why those are good things, read the next two articles!

It also does something much more important to prevent common errors, but I'll explain that later, once you are more familiar with this new "event-driven" style.

Even-driven programming - why you need it on ESP8266

Remember when you were a kid and your dad sat you down for that difficult "birds and bees" talk? Well, there's something we need to get out of the way now:

Programming the ESP8266 properly is not easy. In fact it's pretty tricky.

Sure, if all you want to do is flash an LED a la "blinky" sketch - that's ridiculously easy: pre-teenage kids can do it. But building an IOT infrastructure, writing firmware that will run on ESP-01, Sonoff, Wemos and NodeMCU that will never crash or reboot and will seamlessly reconnect after any network problem and never stop the attached hardware working...i.e. something actually useful, well that's harder. And it's virtually impossible unless you adopt the "event-driven programming" style.

Sure that are a lot of simple examples out there that don't do this - they look just like the code you are already used to writing - but the key is in the word "simple". They are examples to introduce you to a new concept: they are deliberately stripped back to the bare bones help you learn. They cannot hope to also teach you in a few lines of demo code the best way to use the new idea in the real world.

Rocket Science 101 is probably taught using a lot of fireworks, but no-one goes to the moon on one...

So why do you need to start adapting to the event-driven style?

Whatever device you are reading this on will be doing at least a dozen other things too: receiving an incoming SMS, updating your GPS location and playing your favourite tune. We live in an age where we are so used to such things, that we don't even notice it any more, we expect it.

The reason that your device is able to do all of those things apparently at the same time, is that for the last 40 or 50 years, hordes of programmers have learned the techniques of "multitasking" and built systems such as Windows, Linux, IOS, Android which are operating systems (OSs) that allow many things to happen as if at once, so that you don't have to understand muiltitasking when you write programs on those devices. But the ESP8266 doesn't have an operating system* so if you want to do more than one thing at a time, you do need to understand multitasking.

"But" - I hear you say - "I only want to do one thing at a time with my sketch! That's what I've always done with Arduino / AVR / STM32 etc and I didn't have to learn this "multitasking" thing!"

And I reply "Maybe so, but they didn't have built-in WiFi, did they? The ESP gives you no choice: it comes with WiFi built-in, and that's why you bought it. Having that WiFi changes everything - it's not "free" and it has important consequences. The first is that it doesn't operate by magic, it needs CPU time just like your sketch does.

The WiFi code in the ESP8266 needs to run all the time to keep the connection alive, as well as being ready to send and recieve data when your code needs it. So the ESP is partitioned into two sets of code: the WiFi code and your sketch. It is designed to run both at the same time. The main point here is that - unlike many other systems you may be used to - yours is not the only code running. Failing to adapt your coding style to these consequences - in anything but those simple examples - often leads to crashes, exceptions, "random" failures, "watchdog timer" resets and many other forms or programming pain. Event-driven programming is the easiest way to avoid that pain.

Instead of your code saying "do this, do that, then do the other" as you are used to doing, it now needs to say "tell me when X happens, tell me when Y happens and I'll sit here quietly - doing nothing - till you actually do". Buzzword time: The "old" way is called "synchronous" the "new" way is called "asynchronous" as well as "event-driven". Synchronous = you control when things happen, Asynchronous=you don't  - someone else does. In our case, "someone else" is the 200k+ of ESP firmware that manages the WiFi (amongst other things)

Your code has to co-operate and be ready to do what you need when the firmware says its OK. If your code runs in a tight loop or waits for a long time for an external resource (hardware, remote web page etc) and "blocks" the other code from running, bad things happen. This is why sometimes you will also hear about "blocking" (synchronous) and "non-blocking" (asynchronous) code.

To get the best out the ESP8266, you need to write "non-blocking" code.

The most common way of doing that is with "callbacks". A callback is a function that you write that gets called by some other piece of code, when that other code knows it is a good time to do so. You tell the "other" code what you are interested in, and it "calls you back" when the interesting thing happens. Till then you just twiddle your thumbs in the main loop. Telling the other code the name of your function is known as "registering a callback". Luckily for us, many of the libraries that come with the Arduino ESP8266 add-ons are designed this way.

Before we get into more details, let's get some other buzzwords out of the way. Those two "partitions" (your sketch and the WiFi firmware) are sometimes called "threads". Often when a system has only two threads - as in the ESP - they are known as the "background thread" (WiFi) and the "foreground thread" (Your sketch). After "setup" completes, most of your code starts from the "loop" function. So now its easy to understand why your code is sometimes said to "run on the main loop thread". Once the two threads start trying to "talk to each other" is when the fun begins...

The new way of thinking that comes along with the event-driven style is that events can happen at any time and often in a different order from what you might expect. Your code has to be ready. It needs to cope with suddenly being called "out of the blue" and it has to what it needs to do quickly, so that it doesn't block other (more important) code from running.

So now you know why, the next article will start looking into how, but before it does you need to realise that this isn't the end of the story...There are numerous (often complex) other consequences of two pieces of code both wanting to access a single resource (e.g. the CPU, a shared "flag") at the same time and there will be a lot more new buzzwords flying around when we meet them and learn how to deal with them.