The modified AMOS Wireless HAT boards arrived a couple of weeks ago, along with a larger A to D board for easier soldering, and a different 40-pin header that fits much more comfortably onto the Raspberry Pi board pins. I went ahead and populated all of the components, but did notice a few problems during assembly:
1) The relay switch is too big to fit on the top side of the board where it was supposed to go, and the package size for the switch is smaller than I expected, so it was necessary to solder some jumper wires onto the bottom side of the board to connect it.
2) The A to D board extends a bit too far over a terminal block that was intended for the A to D inputs. The input wires can just be soldered to the board directly though, so not a big problem.
3) The USB-serial converter board is dangerously close to the metal shell of the HDMI connector on the Pi board. For testing purposes, a piece of duct tape was stuck over the USB-serial converter board to avoid shorting. The USB-serial converter board is also directly over the camera connector on the Pi board, so there is no room to insert a camera cable. The HAT board needs to include a hole large enough to accommodate a camera cable.
4) A lot of the text that I had added to the second version of the board (company name, website, etc.) is missing from the board. I'm not sure why, but I'll try to figure it out before the next version.
Issues 2 and 3 could have been avoided with better 3D modeling I guess, but 1 and 4 require a board re-design anyway, so little would have been gained by fancy 3D analysis.
Here's what the top of the combined boards looks like when placed inside an electronics enclosure for testing:
You can't really see the wireless sub-module and and USB-serial converter because they are on the bottom side of the HAT board. Even though the compass module and GPS are not installed yet, and the wires from the battery box are not yet connected, it is clear that this should really reduce the amount of wiring, to clean up the enclosure.
This build will be a new shorter prototype AMOS with a single water prop. It won't be solar-powered, but I'm hopeful that it should be quick and speedy for relatively short (< 3 hours) missions. Here are a couple of pics:
Before flicking on the power switch to test it out, I checked for shorts on the 3.3 V and 5 V power lines. There were none, but I was still a bit doubtful that it would work, so I was pleasantly surprised to see the red power LED on the Pi board come on properly when I flipped the switch, and saw some reassuring flickers of the green activity LED also, indicating that the Pi board was busy with the task of booting up.
Initial tests of the A to D function, humidity / temperature sensor, and discovery / setup of the wireless module worked well, however the relay switch for going into sleep mode and the RTC module did not work. I'll need to debug these to figure out what the issues are. I'll also need to hook up the remaining components to test / debug them as well. Once it's ready it will be exciting to take it for a spin! 😊