Hey there Harry
Wanted to give my two cents on your schematic. I’ve made a few dozen boards using the DRV8311. Mostly just the same board several times trying to fix my mistakes lol. A few things I wanted to point out.
I think you have a mistake on the 3.3V supply coming from the DRV8311. The 3.3v regulator will not turn on unless you wake the chip from sleep mode with a logic high signal. In your diagram you’ll power up the 12v supply and then nothing will happen because the drv is still asleep. The stm won’t be able to wake it up since there is no 3.3v supply. I found this one out the hard way…
You might want to break out some UART pins for debugging (TX + RX). Its frustrating not being able to simply read some serial print statements when something isn’t working.
The 3.3v regulator is a linear style and therefore not energy efficient. When you drop from 12v down to 3.3v you have to burn off the remaining 8.7v. If your stm + as5600 draw 60ma then the regulator will be burning (8.7*0.06 = 0.5 watts). I used this before and my circuit was overheating. I had to add a heat sink to keep it running. You might consider doing a dedicated 3.3 linear regulator like the ams1117 which can handle more power dissipation. You can also use it to wake the drv from sleep.
Hope this helps.