Video Fido
"We do these things not because they are easy, but because we thought they would be easy."
Programmers credo
This is a dumb little app I wrote to use an old Raspberry Pi 3B, a cheap st7789 screen and a pre-exsting Frigate and MQTT setup in order to let me know if someone is at the front door.
As with a lot of these sorts of projects, it was a definite "learning experience".
What's it do?
It listens for an event indicating a camera spotted someone, and displays the photo on it's screen for about 10 seconds.
That's it. I have it set up so that it's mostly invisible to me so I know if I need to go answer the door or if I can gleefully ignore whoever.
Isn't this a solved problem?
Yes, yes it is. There are lots of better, fancier, smoother things out there. This is cheap and hacky and private.
Lessons learned
-
Device manufacturers love to give things almost the standardized names.
-
SPI != GPIO, particularly when dealing with a real Raspberry Pi vs a Pico board. (Please don't remind me that even if you can power up multiple displays off a Pico, you've only got one frame buffer.)
-
Things are easier than you think, unless they're very hard indeed.
System Requirements
- Make sure your Pi has GPIO and SPI enabled using
raspi_config - apt install rpi.gpio, python3-spidev
wiring
I included a wiring chart in the code, but since you're here:
| st7789 | pi | |
|---|---|---|
| vcc | purple | 1 (3v3) |
| gnd | white | 6 (Ground) |
| din | green | 19 (GPIO10 SPI0_MOSI) |
| clk | orange | 23 (GPIO11 SPI0_SCLK) |
| cs | yellow | 24 (GPIO08 SPI0_CE0) |
| dc | blue | 21 (GPIO09 SPI0_MISO) |
| rst | brown | 22 (GPIO25) |
| bl | gray | 33 (GPIO33) |
Note for anything other than the SPI0_* pins, you can use any other appropriate power/GPIO pin you want. Just update the code for that line.
many wires were fiddled to bring you this chart
Do I have to run this as root?
yes. The libraries directly access /dev/mem and a number of other deeply protected devices.
Why aren't you using python project.yaml like a modern person?
Because I'm old.
Your code is not elegant.
Who are you, Henry Henderson? Look, this is a crap project I wrote to scratch an itch. I'm posting it because otherwise I'd forget about it and maybe someone else might find it useful. It's not going on my resume.
UPDATE
So, turns out Pico Ws are kinda dumb. Also, circuitPython doesn't do JPGs. So I split Fido into two parts, gidget which is a tiny app meant to run on the Pico which listens for MQTT messages that contain an image to display and ceasar which does the work of listening to Frigate's MQTT, doing the image manipulation, and sending it to gidget. It should work great, except for the fact that the Pico running gidget quickly ran out of memory.
I've added both to this repository for the future.