I’ve been studying the schematics and I noticed 10 pins on the SODIMM connector that are NC for the compute module. They are:
- 124 - MICBIAS → (TRS Connector)
- 126 - MICP → (TRS Connector)
- 128 - MICN → (TRS Connector)
- 130 - IGPIO0 → (PWRON from power IC)
- 132 - IGPIO1 → (??)
- 154 - HPOL → (Audio IC)
- 156 - HPOR → (Audio IC)
- 158 - AUD_SWITCH → (Audio IC)
- 160 - USB0_DP → DB_P (USB IC)
- 162 - USB0_DM → DB_N (USB IC)
All of these pins on the pi compute module are NC. So perhaps the A04 and A06 modules have more capabilities with access to these pins? At the very least, I think I can say that the pi won’t have audio input support from the TRS jack, but maybe the A04/A06 will?
Does anyone have insight into some of these pins? Seems like the main thing is that audio might be handled differently between the two types of boards.
EDIT: For reference here are the pins from the DevTerm schematics overlayed with raspberry pi’s pin documentation: