【经验】EFR32FG23无线SoC芯片使用IADC的single interrupt方式读取芯片引脚AD值的方法

本文以SILICON LABS EFR32FG23无线SoC芯片的rail_soc_simple_trx工程为例，介绍EFR32FG23芯片使用IADC的single interrupt方式读取芯片引脚AD值的方法。

1、在rail_soc_simple_trx工程中双击打开rail_soc_simple_trx.slcp文件，点击SOFTWARE COMPONENTS，在搜索栏输入iadc，点击搜索到的IADC组件，点击Install。

2、在工程中添加如下头文件：

#include "em_cmu.h"

#include "em_iadc.h"

#include "app_log.h"

3、在工程中添加IADC CLK和IADC输入引脚的定义代码，本文使用10MHz的ADC CLK，使用PA5来采集AD数据。

// Set CLK_ADC to 10 MHz

#define CLK_SRC_ADC_FREQ        20000000  // CLK_SRC_ADC

#define CLK_ADC_FREQ            10000000  // CLK_ADC - 10 MHz max in normal mode

#define IADC_INPUT_0_PORT_PIN     iadcPosInputPortAPin5;

#define IADC_INPUT_0_BUS          ABUSALLOC

#define IADC_INPUT_0_BUSALLOC     GPIO_ABUSALLOC_AODD0_ADC0

4、在工程中添加两个变量，用来存放IADC采样数据和最终的电压数据。

// Raw IADC conversion result

static volatile IADC_Result_t sample;

// Result converted to volts

static volatile double singleResult;

5、在工程中添加IADC的初始化代码。

void initIADC(void)

{

  // Declare initialization structures

  IADC_Init_t init = IADC_INIT_DEFAULT;

  IADC_AllConfigs_t initAllConfigs = IADC_ALLCONFIGS_DEFAULT;

  IADC_InitSingle_t initSingle = IADC_INITSINGLE_DEFAULT;

  // Single input structure

  IADC_SingleInput_t singleInput = IADC_SINGLEINPUT_DEFAULT;

  /*

   * Enable IADC0 and GPIO register clock.

   *

   * Note: On EFR32xG21 devices, CMU_ClockEnable() calls have no effect

   * as clocks are enabled/disabled on-demand in response to peripheral

   * requests.  Deleting such lines is safe on xG21 devices and will

   * reduce provide a small reduction in code size.

   */

  CMU_ClockEnable(cmuClock_IADC0, true);

  CMU_ClockEnable(cmuClock_GPIO, true);

  // Use the FSRC0 as the IADC clock so it can run in EM2

  CMU_ClockSelectSet(cmuClock_IADCCLK, cmuSelect_FSRCO);

  // Set the prescaler needed for the intended IADC clock frequency

  init.srcClkPrescale = IADC_calcSrcClkPrescale(IADC0, CLK_SRC_ADC_FREQ, 0);

  // Shutdown between conversions to reduce current

  init.warmup = iadcWarmupNormal;

  /*

   * Configuration 0 is used by both scan and single conversions by

   * default.  Use unbuffered AVDD as reference and specify the

   * AVDD supply voltage in mV.

   *

   * Resolution is not configurable directly but is based on the

   * selected oversampling ratio (osrHighSpeed), which defaults to

   * 2x and generates 12-bit results.

   */

  initAllConfigs.configs[0].reference = iadcCfgReferenceVddx;

  initAllConfigs.configs[0].vRef = 3300;

  initAllConfigs.configs[0].osrHighSpeed = iadcCfgOsrHighSpeed2x;

  /*

   * CLK_SRC_ADC must be prescaled by some value greater than 1 to

   * derive the intended CLK_ADC frequency.

   *

   * Based on the default 2x oversampling rate (OSRHS)...

   *

   * conversion time = ((4 * OSRHS) + 2) / fCLK_ADC

   *

   * ...which results in a maximum sampling rate of 833 ksps with the

   * 2-clock input multiplexer switching time is included.

   */

  initAllConfigs.configs[0].adcClkPrescale = IADC_calcAdcClkPrescale(IADC0,

                                                                     CLK_ADC_FREQ,

                                                                     0,

                                                                     iadcCfgModeNormal,

                                                                     init.srcClkPrescale);

  /*

   * Specify the input channel.  When negInput = iadcNegInputGnd, the

   * conversion is single-ended.

   */

  singleInput.posInput   = IADC_INPUT_0_PORT_PIN;

  singleInput.negInput   = iadcNegInputGnd;

  // Allocate the analog bus for ADC0 inputs

  GPIO->IADC_INPUT_0_BUS |= IADC_INPUT_0_BUSALLOC;

  // Initialize IADC

  IADC_init(IADC0, &init, &initAllConfigs);

  // Initialize a single-channel conversion

  IADC_initSingle(IADC0, &initSingle, &singleInput);

  // Clear any previous interrupt flags

  IADC_clearInt(IADC0, _IADC_IF_MASK);

  // Enable single-channel done interrupts

  IADC_enableInt(IADC0, IADC_IEN_SINGLEDONE);

  // Enable IADC interrupts

  NVIC_ClearPendingIRQ(IADC_IRQn);

  NVIC_EnableIRQ(IADC_IRQn);

}

6、在工程中添加IADC的中断处理函数，在处理函数中打印最终的电压数据。

void IADC_IRQHandler(void)

{

  // Read a result from the FIFO

  sample = IADC_pullSingleFifoResult(IADC0);

  /*

   * Calculate the voltage converted as follows:

   *

   * For single-ended conversions, the result can range from 0 to

   * +Vref, i.e., for Vref = AVDD = 3.30 V, 0xFFF represents the

   * full scale value of 3.30 V.

   */

  singleResult = sample.data * 3.3 / 0xFFF;

  app_log_info("IADC Result: %.2f\n", singleResult);

  /*

   * Clear the single conversion complete interrupt.  Reading FIFO

   * results does not do this automatically.

   */

  IADC_clearInt(IADC0, IADC_IF_SINGLEDONE);

}

7、在main()函数中添加initIADC();来初始化IADC。

8、在工程中合适的位置调用IADC_command(IADC0，iadcCmdStartSingle);来读取AD值。

9、本文在测试时使用稳压电源给EFR32FG23芯片的PA5引脚供2.5 V的电压。

10、EFR32FG23芯片通过IADC读取到电压为2.48~2.49V之间，使用IADC成功读取到芯片引脚的AD值。