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();
    }
  }
}