My V1 of a HAT for the M1. I'm expecting some revisions will be required (especially tweaking trace widths) but am away soon for a bit so figured I'd get some boards made and test the basics with it.
Slightly wider than the M1 board which is not ideal. It has a 4 channel dew heater control and stepper drivers for a focuser and rotator on board. I could easily remove 2 dew heater channels for my use and retrieve some width in the board but for now it's mostly a learning exercise rather than an attempt to get the final board. I'd not opto isolated the FET circuits in the original Android version of this but have added it this time.

Not tried with this version but I have pondered putting some components upside down to see if a simplified version would fit in the official case with access via the back.
I have not done PCP mounted sockets for the 12V supply or I2C bus at this stage. I2C to talk to a Temp/Humidity sensor to measure ambient conditions. Headers on the board for both currently but version 2 will probably do that differently. I hope there are no I2C or 1-wire conflicts with the M1, I use both, Dallas 1-wire temp sensors under the heater straps to try and track heating.