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Power and ADC Notes

Last revised: 2026-06-10 (pin models re-checked against the variants).

ADC and power-path distinction

The package distinguishes three concepts:

  • normal external analog pins,
  • a dedicated board VBAT pin that consumes one ADC-capable input,
  • the nRF52 VDDHDIV5 internal measurement path (the divided high-voltage supply, no external pin involved).

Reading them from a sketch

int raw  = analogRead(A0);           // any external analog pin
int vdd  = analogReadVDD();          // the MCU supply itself
int div5 = analogReadVDDHDIV5();     // VDDH / 5 internal path

bool ok      = nrfBatteryReadingSupported();
int  batt    = nrfBatteryRaw();         // routes to the board's model below
uint32_t mv  = nrfBatteryMillivolts();  // same reading, converted

NrfBoardPowerInfo (see NrfBoard.h) reports which model a board uses at runtime: batterySenseAvailable, batterySenseViaVddhDiv5, and batterySensePin (0xFF when the board has no dedicated pin).

Board-level battery models

Board Model
promicro_nrf52840 VBAT divider on public pin A1 / D16 (P0.29)
nicenano_v2 VDDHDIV5 (no public battery pin)
supermini_nrf52840 VDDHDIV5 (no public battery pin)
nrfmicro_nrf52840 dedicated VBAT pin (P0.04)
mini_nrf52840 public pin 31
pitaya_go_nrf52840 public pin 28
xiao_nrf52840, devboard_*, usb_dongle_nrf52840 no battery sense modeled (PIN_BATTERY = 255)

Practical caveats

  • When a board uses a public VBAT pin, that pin is no longer a free generic analog input in practical board usage.
  • When a board uses VDDHDIV5, there is no dedicated public battery pin; battery reads come from the internal divided supply path, which only makes sense when the battery actually feeds VDDH.
  • Battery percentage interpretation (divider ratios, chemistry curves) is out of scope for the core — it returns the raw ADC reading of the modeled path.