Today I've made some further experiments on RP debug connector and I've found out when pulling pin 5 low, MPU gives the following output when battery power is applied:
RSTFLG : 0009
!!!MPU Forced Wakeup!!!
setCCSnkRst
disableBattUVLOInt
Reg0D: 00/00, Reg14: 7F/7F
setCCSnkRst
E0ON
E1ON
initBattery
MON>>>sw task Initialize Complete
/USB_DET undetected
batt task Initialize Complete
adapter task Initialize Complete
temp task Initialize Complete
disp task Initialize Complete
acc task Initialize Complete
setCCSnkRst
This will boot MPU and ICU, even when battery door is open, and also won't shut it down when opening battery door. Thus the last unknown pin is
/MPU_FORCED_WAKEUPWe do now know the full pinout of the debug connector of modern cams (200D, R, RP, R6, R5 etc.):
1: VCC_ICU (1v8)
2: RX_ICU (1v8)
3: TX_ICU (1v8)
4: GND
5: /MPU_FORCED_WAKEUP (3v3)
6: TX_MPU (3v3)
7: RX_MPU (3v3)
8: VCC_MPU (3v3)
It's not possible to power camera through debug connector, as not all parts in camera will be supplied with power. MPU will refuse to boot with low battery warning. Therefore I think the pins are meant so be "sense' pins, so one does now if MPU and ICU are currently powered. Instead 7.2V have to be provided via battery connector, or alternatively via the test pads next to it:
