I'm getting a strange amount of error when trying to measure the battery for a custom PCB based on the nrf9160.
Details
- My VCC_IO is 1.8V
- My max battery voltage is 4.2V
- I am using a slightly modified version of the battery sample from zephyr/samples/boards/nrf/battery.
- I'm using a switch controlled voltage divider, where R1 is 3.01k and R2 is 2.0k
- I am measuring the analog levels on adc line, the battery voltage going into the divider, and the battery voltage going into the switch.
- I am using the internal reference of 600 mv.
- I am using ADC_GAIN_1_3
- 600mv * 3 = 1800 mv (Within VCC_IO + 300 mv)
- An analog value of 145 mv should result in a value of around 3630 mv to be reported from the device.
- The device is reporting battery voltage of ~3570 mv.
This isn't necessarily useful information, but I have another custom PCB with an almost identical measurement circuit but VCC_IO is 3.0V. The device always reports an acceptable value.
Am I missing something here?
