XIAO_BLE_Sense(mbed 2.7.2) battery charge and voltage monitor, analogRead(P0_31) does not work

[msfujino]

Hi braddo,
The problem in this post only occurs with the combination of the board “Seeed XIAO_nRF52840” and the board library “Seeed nRF52 mbed-enabled Borads 2.7.2/2.8.1/2.9.0”.
For more information about your board “XIAO_ESP32C3”, please see the following link.

Battery voltage monitor and AD conversion for XIAO_ESP32C

The battery pad of XIAO_ESP32C3 is not connected to any port, so the battery voltage cannot be read and there is a risk of over-discharging the battery. (XIAO_BLE has a port connected to the pad and can read the voltage.) The battery voltage was divided by 1/2 with 200k and connected to the A0 port so that the voltage could be monitored. About the AD conversion of the ESP32C3 The datasheet says nominally 2500mV full scale AD conversion, but there is a large variation from chip to chip, actua…