XIAO BLE Sense battery level and charging status

Excellent Forum Solutions XIAO
38

I noticed that if you let one full battery reading complete using @POPOBE97 's code before setting the green LED to output mode, you can continue to use both the green LED and measure the onboard battery level.

I’m now able to use all the LEDs, Bluetooth, the microphone, the IMU, and read the battery level, all at the same time.

#include <nrf52840.h>
#include <nrfx_saadc.h>
#include <AnalogIn.h>
#include <pinDefinitions.h>

// Reading Battery Level
// https://forum.seeedstudio.com/t/xiao-ble-sense-battery-level-and-charging-status/263248/24

class HackAnalogIn: public mbed::AnalogIn 
{
  using mbed::AnalogIn::AnalogIn;
  public:
    analogin_t getAnalogIn_t();
};

analogin_t HackAnalogIn::getAnalogIn_t() 
{
  return this->_adc;
}

void startReadingBatteryLevel(nrf_saadc_value_t* buffer) 
{
  auto pin = PIN_VBAT;
  PinName name = analogPinToPinName(pin);
  if (name == NC)
  {
    return;
  }
  HackAnalogIn* adc = static_cast<HackAnalogIn*>(analogPinToAdcObj(pin));
  if (adc == NULL)
  {
    adc = new HackAnalogIn(name);
    analogPinToAdcObj(pin) = static_cast<mbed::AnalogIn*>(adc);
#ifdef ANALOG_CONFIG
    if (isAdcConfigChanged)
    {
      adc->configure(adcCurrentConfig);
    }
#endif
  }

  nrfx_saadc_buffer_convert(buffer, 1);
  nrfx_err_t ret = nrfx_saadc_sample();
  if (ret == NRFX_ERROR_BUSY)
  {
    // failed to start sampling
    return;
  }
}

nrf_saadc_value_t BatteryLevel = { 0 };

float vBat = 0.0;

void monitor_battery_level(void){
  // Monitor the Battery Level
  static unsigned long _lastT = 0;
  unsigned long _t = millis();

  if (_t - _lastT > 1000)
  {
    // read battery level every 1 second
    startReadingBatteryLevel(&BatteryLevel);
    _lastT = _t;
    Serial.print("startReadingBatteryLevel at time ");
    Serial.println(_t);
  }

  // check if ADC conversion has completed
  if (nrf_saadc_event_check(NRF_SAADC_EVENT_DONE))
  {
    // ADC conversion completed. Reading is stored in BatteryLevel
    nrf_saadc_event_clear(NRF_SAADC_EVENT_DONE);
     vBat = (float)BatteryLevel / 4096 * 3.3 / 510 * (1000 + 510);
    // write value to characteristic or things you want to do
    
    Serial.print("BatteryLevel: ");
    Serial.println(vBat);
  }
}
void setup()
{
  Serial.begin(115200);
  //while (!Serial);

  Serial.println("Battery Level Example!");  

  // Battery Level setup
  pinMode(P0_14, OUTPUT);
  digitalWrite(P0_14,LOW);
  
  while(vBat == 0.0){
    monitor_battery_level();
  }
  
  pinMode(LEDR, OUTPUT);
  pinMode(LEDG, OUTPUT); // Setting LEDG to pinMode OUTPUT casues the monitoring of Battery Level to stop working
  pinMode(LEDB, OUTPUT);
  digitalWrite(LEDR,HIGH);
  digitalWrite(LEDG,LOW);
  digitalWrite(LEDB,HIGH);

}

void loop()
{
  monitor_battery_level();
}
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