Does the B402 have an equivalent of the EN pin found on other boards? I only see MODE and RESET. I would like to connect 402s to the AB1805 hardware watchdog mentioned in the docs and get deep power off functionality, but its not looking possible.
The B Series SoM does not have EN-pin functionality, because it would go into the power supply circuitry, which is on your base board, not on the SoM itself.
I’ve used a circuit like this, using a SIP32510 load switch, but any load switch can be used for this purpose.
The Boron uses a circuit like this, using a XC8107SOT25:
- If you are using a PMIC, put the load switch on VSYS, shutting off power to both the cellular modem and 3.3V power supply.
- Otherwise put it an any appropriate location to be able to turn off those two things.
Also you should never remove power abruptly like that with the B402/B404 because it could damage the cellular modem. See TAN004 for more information.