Thursday, 9 February 2017

MakeTronix Alarm and GPIOZero on Raspberry Pi

I funded the MakeTronix Alarm on IndieGoGo because it contains many of the components I usd with Raspberry Pi at CoderDojo, but in one compact package. Don't get me wrong, I'm all in favour of having learners build the circuit using a breadboard, but sometimes there just isn't the time to do that and code it.

The board arrived very quickly and it is a nice, neat package. I was pleased that they kept the board to 26 pins as this will enable it to work with my trusty set of original mode Bs.

The online documentation is easy to find but I have to say I found it a little disappointing. It seems weird to not show a picture of the board mounted on a Pi in the “connecting the board” section. The written description is entirely accurate but a simple diagram would be much better, especially for younger users. I was also surprised to find that the code examples downloaded from the MakeTronix github don't use gpiozero. There's nothing wrong with using the Rpi.GPIO library – it works perfectly – but I believe  gpiozero is much better for those who are new to Python and this board is being marketed as a “fantastic educational circuit board for learning programming”. They've tried to abstract out the key functions into a library file that the other examples import, but this feels a bit unwieldy, again especially for novice Pythonistas.

I also couldn't get the full alarm code to work. It turned out this was nothing to do with the code: the PIR that shipped with my kit didn't work correctly and would not trigger on motion at any sensitivity. Luckily I have plenty of these PIRs and substituting in a replacement got everything working.

Nevertheless I decided to write a gpiozero version. It uses a couple of lambda functions which you might argue are too opaque for beginners (and I'd probably agree) but they do remove the need to give each button its own when_pressed function individually.

Here's why I love gpiozero – all sorts of hardware control is possible with simple, easy to understand syntax. My MTAlarm code does the following:

1. Activates the PIR and waits for motion to be detected. The LED glows/pulses to indicate that the alarm is active.

2. When motion is detected, the LED starts flashing.

3. If within 10 seconds  the correct code is entered (each key beeps when pressed and DEL acts as backspace) the alarm is disabled.

If not, the buzzer starts to beeeeeep constantly.