Test Air Quality with the EMF Badge

The air here seems ok

The air here seems ok

One of the (many) wonderful things about the electromagnetic fields event I went to was the badge that everyone was given. This was an embedded device with a nice colour screen and a powerful processor that just happened to be a mobile phone as well…… I thought I’d turn it into an air quality display. So I 3D printed a case and make some modifications so that I could fit an air quality sensor and a battery to power it on the back of the badge. This is the back of the badge:

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The hardware construction went fine, and I had the badge and the sensor exchanging messages quite nicely. Then I tried to write the software and it all went wrong. So I gave up and decided to enjoy the event instead….

However, I’m not a quitter. So, after a lot of fun and games, I’ve finally submitted my air quality app to the badge store for the emf badge. You can find it in amongst the other apps in the store here. It seems to work a treat and I can wear it around my neck with pride. Although I guess this would probably look a bit silly around Hull, where a lot fewer people seem to be wearing emf badges than there were at the event.

Anyhoo, one significant (at least for me) takeway is that if you want to use the serial port in MicroPython in binary mode (i.e. not have the driver mess around with carriage return and linefeed characters), you can use a special option to request this:

sensor_port = UART(2,9600, bits=8, mode=UART.BINARY, parity=None, stop=1)

This option is, of course, undocumented on the MicroPython pages for the UART class, leading to endless hours of “fun” for developers (like me) who spend ages wondering why their binary checksum values are all wrong…..