Well, things have been going a bit slowly for a few days.
I discovered that I very nearly made a huge mistake on the robot. I thought I would be able to shift the position of the bumpers upwards to clear the USB port of the Pico. That wasn’t actually correct.
The way I have designed them makes it impossible to change the position of the PCB on the mounting bracket after gluing on the foam pad, because the screw heads are behind the front bumper and foam. I was looking at having to saw off half the mounting bracket and re-drill all the holes and so on.
Instead, I reluctantly decided to flip the main board over and mount it on the underside of the top deck, instead of the lower deck. It works. It’s fine. But now I find that the cable to the motor driver is too short by just a little bit. It reaches but it’s tight, so I’ll have to make another one.
I built another main circuit board. When I did the etching I had 3 patterns on the transparency, resulting in 3 boards. Making up another board means I’ve used up all the header pins I just purchased. That’s okay. I’ll head back to Jaycar and get some more, but each board uses 80 pins.
I’ve finally ordered some needed parts. I figured I wasn’t getting any value from having 0.02 Etherium sitting idle, so I liquidated that. Bought it for $50 and sold for $153, so not a bad investment. That was enough to get the power modules I needed, some more Picos, sonar modules and OLED displays.
I’m a bit annoyed that the sonar modules run at 5v, but they have separate trigger and signal pins, so I can voltage divide the signal so it’s safe for the Pico. Perhaps I will do that with a bit of soldering on the sonar deck itself. The other issue I have is that I’ve designed the board to supply 3.3v to the sonar deck, so I’ll need to figure out how to get access to 5v.
Looking at the Circuit Python API, it looks as if I will be able to drive the OLED displays easily enough, so that will be fun. I’m not entirely sure where I want to mount the display. I kinda like the idea of mounting it behind the structural acrylic, between the front and rear wheels. That has viewability issues however, so I might end up mounting it on the top deck.
I ended up buying some more Raspberry Pi Pico Ws for $10 each. I noticed that the non W version is going for $3.99 at Raspberry Pi Australia and $4.99 at Littlebird, which is the same company but with a different storefront so not sure what’s going on there. I maybe should have picked up some non W Picos, because postage will kill any prices savings.