Now it's time to assemble the boards. The microcontroller part was easy, and I got the bootloader on it to test that everything works. The hard part is the accelerometer and matrix driver chips, as they are QFN. Especially the driver is scary, with its 48 pins. Let's see if my new super power, the hot air gun, will give me an upper hand here.

It's soldered and an inspection under magnification suggests it's all fine. You can see the bodge wire I had to add for one of the resistors, because I pulled the pin down while it should be pulled up. The accelerometer is LIS3DH, and I simply desoldered it from a module. A quick build of the CircuitPython firmware, and I verified that both the accelerometer and the driver enumerate on the I2C bus. Yay!

So I guess I just solder the matrices and pray it works. Of course I initially started soldering the first matrix the wrong way around — but fortunately I noticed after just a few pins, and managed to desolder it and rotate properly. The text on the matrix needs to point to the right of the board, where the fire buttons are.

Then I just copied the library from the #PewPew FeatherWing, and I tried to display a filled rectangle:

The good news is that it displays something! The bad news is that I still need to do that "I will fix it in software" re-numbering of rows and columns. Oh well, it would be probably completely impossible to route if I insisted on keeping the order.