Chez Toi IOT design goals 2

Design Goals 2:

• OTA updates
• Compatibility with a variety of hardware
• Common fundamental interface for all devices
• Minimal functionality per device - "intelligence" added in central controller
• Control of "slave" RF 433MHz devices

OTA updates

A "no-brainer" - I can't climb ladders or rip open walls to press flash upload buttons. It's as simple as that. Some of devices will be on barn roofs and/or 100m from the house and it gets cold and wet in winter here...

There's a conflict here with the next goal, as the cheapest and smallest ESP8266 device (the ESP-01) doesn't come with enough flash RAM to support OTA updates. This is because to do so, a device has to have RAM at least 2x the size of the upload. ToiioT firmware weighs in at 300k+ and the '01 has 512k RAM - "do the maths" as they say. Happily the more recent ESP-01S variant has 1M - now we are cooking again, except...(It also has a couple of very subtle other differences that will bite you...)

Compatibility with a variety of hardware

Once I had discovered how easy and cheap the Sonoff range of devices are to re-flash with your own firmware, I thought "why use anything else?". Well, because they don't do much other than switch things on and off. That's great if that's all you want and in many cases, I do. But once you need to add PIR sensors etc etc etc. you need more pins.

Hence a heavy reliance on the Wemos D1, whose praises I cannot sing loudly enough. What a gem of a device and - again - an ever-present deign goal for me: cheap as chips.

Common fundamental interface for all devices

All "trucs" have a push button and an LED, whether they came built with it or not. In all of them, the action is the same:

Short press: device on/off

Medium press: LED flashes rapidly, device reboots on release

Long press: LED flashes high-speed, device "factory resets" on release

...all "just in case" and utterly, utterly essential during development.

Minimal functionality per device - "intelligence" added in central controller

The layout of my home is such that I want the landing light to come on when motion is detected. There are 5 choices: The 3 bedrooms, the bathroom or someone coming up the stairs.

I don't want "bedroom 1" controller to be "linked" by its inbuilt logic to the landing light, because tomorrow it may actually be "outside barn no 2" controller. So each sensor device is just a "dumb" box: "something moved". "I heard a noise". "It just went dark" etc.

The raspberryPi controller is what "wires" the devices together. It's got a lot more "grunt" and is a lot easier to program if you use the wonderful NODE-RED software. I have to have one anyway as my own "cloud" / MQTT controller. So NODE-RED receives the MQTT message "I'm truc27, something just moved" and says, "OK then, lets tell trucs11, 13 and 15 to switch on, and 7 to go off" - all by virtue of visually dragging and dropping a few virtual "wires".

When I move the same device somewhere else, I just "re-wire" NODE-RED in a matter of seconds.

Control of "slave" RF 433MHz devices

This one came very recently to the party. I have no overhead lights upstairs. When I moved in 3 years ago, I purchased some very cheap 433MHz RF sockets. I think I paid 14eu for three of them and a controller. I hate waste, so I thought it would be a wonderful and cheap way of adding to the ToiioT ecosystem to have the "big box of sensors" each be able to have a number of "slave" units.

So when truc9 says "someone touched me", NODE-RED tells truc14 to switch on. truc14 then autonomously happens to also send RF codes to its two floor lamps and bingo: Main light on, incidental lighting on - all for the price of one complex box and two cheapies I already owned.