InfiniTime/src/components/battery/BatteryController.cpp

#include "BatteryController.h"
#include <hal/nrf_gpio.h>
#include <nrfx_saadc.h>
#include <libraries/log/nrf_log.h>
#include <algorithm>
#include <math.h>

using namespace Pinetime::Controllers;

Battery *Battery::instance = nullptr;

Battery::Battery() {
  instance = this;
}

void Battery::Init() {
  nrf_gpio_cfg_input(chargingPin, (nrf_gpio_pin_pull_t)GPIO_PIN_CNF_PULL_Pullup);
  nrf_gpio_cfg_input(powerPresentPin, (nrf_gpio_pin_pull_t)GPIO_PIN_CNF_PULL_Pullup);
}

void Battery::Update() {

  isCharging = !nrf_gpio_pin_read(chargingPin);
  isPowerPresent = !nrf_gpio_pin_read(powerPresentPin);
  
  if ( isReading ) return;
  // Non blocking read
  samples = 0;
  isReading = true;
  SaadcInit();	

	nrfx_saadc_sample();
  
}

void Battery::adcCallbackStatic(nrfx_saadc_evt_t const *event) {
  instance->SaadcEventHandler(event);
}

void Battery::SaadcInit() {
  nrfx_saadc_config_t adcConfig = NRFX_SAADC_DEFAULT_CONFIG;
  APP_ERROR_CHECK(nrfx_saadc_init(&adcConfig, adcCallbackStatic));

  nrf_saadc_channel_config_t adcChannelConfig = {
          .resistor_p = NRF_SAADC_RESISTOR_DISABLED,
          .resistor_n = NRF_SAADC_RESISTOR_DISABLED,
          .gain       = NRF_SAADC_GAIN1_5,
          .reference  = NRF_SAADC_REFERENCE_INTERNAL,
          .acq_time   = NRF_SAADC_ACQTIME_3US,
          .mode       = NRF_SAADC_MODE_SINGLE_ENDED,
          .burst      = NRF_SAADC_BURST_ENABLED,
          .pin_p      = batteryVoltageAdcInput,
          .pin_n      = NRF_SAADC_INPUT_DISABLED
  };
  APP_ERROR_CHECK(nrfx_saadc_channel_init(0, &adcChannelConfig));
  APP_ERROR_CHECK(nrfx_saadc_buffer_convert(&saadc_value, 1));

}

void Battery::SaadcEventHandler(nrfx_saadc_evt_t const * p_event) {

    const float battery_max = 4.18; // maximum voltage of battery ( max charging voltage is 4.21 )
    const float battery_min = 3.20; // minimum voltage of battery before shutdown ( depends on the battery )

    if (p_event->type == NRFX_SAADC_EVT_DONE) {
      
      APP_ERROR_CHECK(nrfx_saadc_buffer_convert(&saadc_value, 1));

      voltage = (static_cast<float>(p_event->data.done.p_buffer[0]) * 2.04f) / (1024 / 3.0f);
      voltage = roundf(voltage * 100) / 100;

      percentRemaining = static_cast<int>(((voltage - battery_min) / (battery_max - battery_min)) * 100);

      percentRemaining = std::max(percentRemaining, 0);
      percentRemaining = std::min(percentRemaining, 100);

      percentRemainingBuffer.insert(percentRemaining);

      samples++;
      if ( samples > percentRemainingSamples ) {
        nrfx_saadc_uninit();
        isReading = false;
      } else {
        nrfx_saadc_sample();
      }
    }
  }