How to create periodic timer event and use iADC for EFR32 series 2 to do battery voltage monitor in GSDK 4.x and EmberZnet 7.x

How to create periodic timer event and use iADC for EFR32 series 2 to do battery voltage monitor in GSDK 4.x and EmberZnet 7.x

1. Add the following code in app.c

#define _IADC_

#ifdef _IADC_
#include "em_device.h"
#include "em_chip.h"
#include "em_cmu.h"
#include "em_iadc.h"
#include "em_gpio.h"
#endif //#ifdef _IADC_

#ifdef _IADC_
#define CLK_SRC_ADC_FREQ          20000000 // CLK_SRC_ADC
#define CLK_ADC_FREQ              10000000 // CLK_ADC - 10MHz max in normal mode
/*
 * Specify the IADC input using the IADC_PosInput_t typedef.  This
 * must be paired with a corresponding macro definition that allocates
 * the corresponding ABUS to the IADC.  These are...
 *
 * GPIO->ABUSALLOC |= GPIO_ABUSALLOC_AEVEN0_ADC0
 * GPIO->ABUSALLOC |= GPIO_ABUSALLOC_AODD0_ADC0
 * GPIO->BBUSALLOC |= GPIO_BBUSALLOC_BEVEN0_ADC0
 * GPIO->BBUSALLOC |= GPIO_BBUSALLOC_BODD0_ADC0
 * GPIO->CDBUSALLOC |= GPIO_CDBUSALLOC_CDEVEN0_ADC0
 * GPIO->CDBUSALLOC |= GPIO_CDBUSALLOC_CDODD0_ADC0
 *
 * ...for port A, port B, and port C/D pins, even and odd, respectively.
 */
#define IADC_INPUT_0_PORT_PIN     iadcPosInputAvdd;
#define IADC_INPUT_1_PORT_PIN     iadcNegInputGnd;

#define IADC_INPUT_0_BUS          BBUSALLOC
#define IADC_INPUT_0_BUSALLOC     GPIO_BBUSALLOC_BEVEN0_ADC0
#define IADC_INPUT_1_BUS          BBUSALLOC
#define IADC_INPUT_1_BUSALLOC     GPIO_BBUSALLOC_BODD0_ADC0

/*******************************************************************************
 ***************************   GLOBAL VARIABLES   *******************************
 ******************************************************************************/

static volatile int32_t sample;
static volatile double singleResult; // Volts

static sl_sleeptimer_timer_handle_t bat_volt_read_periodic_timer;
static void bat_volt_read_periodic_timer_callback(sl_sleeptimer_timer_handle_t *handle, void *data)
{
  (void)handle;
  (void)data;
  // Start IADC conversion
  IADC_command(IADC0, iadcCmdStartSingle);

  // Wait for conversion to be complete
  while((IADC0->STATUS & (_IADC_STATUS_CONVERTING_MASK
              | _IADC_STATUS_SINGLEFIFODV_MASK)) != IADC_STATUS_SINGLEFIFODV); //while combined status bits 8 & 6 don't equal 1 and 0 respectively

  // Get ADC result
  sample = IADC_pullSingleFifoResult(IADC0).data;

  // Calculate input voltage:
  // For differential inputs, the resultant range is from -Vref to +Vref, i.e.,
  // for Vref = VBGR = 2.42V, and with analog gain = 0.5, 12 bits represents
  // 4.84V full scale IADC range.
  singleResult = (sample * 4.84) / 0xFFF;

}
/**************************************************************************//**
 * @brief  Initialize IADC function
 *****************************************************************************/
void initIADC (void)
{
  // Declare init structs
  IADC_Init_t init = IADC_INIT_DEFAULT;
  IADC_AllConfigs_t initAllConfigs = IADC_ALLCONFIGS_DEFAULT;
  IADC_InitSingle_t initSingle = IADC_INITSINGLE_DEFAULT;
  IADC_SingleInput_t initSingleInput = IADC_SINGLEINPUT_DEFAULT;

  // Enable IADC0 and GPIO clock branches

  /* Note: For EFR32xG21 radio devices, library function calls to
   * CMU_ClockEnable() have no effect as oscillators are automatically turned
   * on/off based on demand from the peripherals; CMU_ClockEnable() is a dummy
   * function for EFR32xG21 for library consistency/compatibility.
   */
  CMU_ClockEnable(cmuClock_IADC0, true);
  CMU_ClockEnable(cmuClock_GPIO, true);

  // Reset IADC to reset configuration in case it has been modified by
  // other code
  IADC_reset(IADC0);

  // Select clock for IADC
  CMU_ClockSelectSet(cmuClock_IADCCLK, cmuSelect_FSRCO);  // FSRCO - 20MHz

  // Modify init structs and initialize
  init.warmup = iadcWarmupKeepWarm;

  // Set the HFSCLK prescale value here
  init.srcClkPrescale = IADC_calcSrcClkPrescale(IADC0, CLK_SRC_ADC_FREQ, 0);

  // Configuration 0 is used by both scan and single conversions by default
  // Use internal bandgap (supply voltage in mV) as reference
  initAllConfigs.configs[0].reference = iadcCfgReferenceInt1V2;
  initAllConfigs.configs[0].vRef = 1210;
  initAllConfigs.configs[0].analogGain = iadcCfgAnalogGain1x;

  // Divides CLK_SRC_ADC to set the CLK_ADC frequency
  initAllConfigs.configs[0].adcClkPrescale = IADC_calcAdcClkPrescale(IADC0,
                                             CLK_ADC_FREQ,
                                             0,
                                             iadcCfgModeNormal,
                                             init.srcClkPrescale);

  // Assign pins to positive and negative inputs in differential mode
  initSingleInput.posInput   = IADC_INPUT_0_PORT_PIN;
  initSingleInput.negInput   = IADC_INPUT_1_PORT_PIN;

  // Initialize the IADC
  IADC_init(IADC0, &init, &initAllConfigs);

  // Initialize the Single conversion inputs
  IADC_initSingle(IADC0, &initSingle, &initSingleInput);

  // Allocate the analog bus for ADC0 inputs
  GPIO->IADC_INPUT_0_BUS |= IADC_INPUT_0_BUSALLOC;
  GPIO->IADC_INPUT_1_BUS |= IADC_INPUT_1_BUSALLOC;
}
#endif//#ifdef _IADC_

2. Add the following codes in emberAfMainInitCallback

#ifdef _IADC_
  initIADC();
  sl_sleeptimer_start_periodic_timer(&bat_volt_read_periodic_timer, 1000, bat_volt_read_periodic_timer_callback, NULL, 0, 0);
#endif //#ifdef _IADC_

3. Battery voltage input to AVDD would be read to singleResult in bat_volt_read_periodic_timer_callback every second.