ADC One Shot and Polling Mode

This sample code guide is designed to help users easily and comprehensively understand ADC sample. This sample demonstrates how ADC samples data by polling mode in one shot mode. This sample uses one shot mode of ADC peripheral to measure voltage on P0_1, VBAT, and VADP by polling mode.

Requirements

For hardware requirements, please refer to the Requirements.

Wiring

1. Connect P0_1 of EVB to external DC voltage source and input voltage of P0_1 must range from 0 to 3.3V.

2. Connect Lithium-ion battery to EVB.

3. Connect VADP to 5V of EVB.

Configurations

The entry function is as follows, call this function in main() to run this sample code. For more details, please refer to the Initialization.

adc_polling_demo();

Building and Downloading

For building and downloading, please refer to the Building and Downloading.

Experimental Verification

Press the Reset button on the EVB board, after initialization is complete, the ADC begins sampling. Once ADC sampling is finished, the raw data collected and the converted voltage values will be printed in Debug Analyzer.

driver_adc_init: data[0] xxx, data[1] xxx, data[2] xxx
driver_adc_init: res[0] xxx, res[1] xxx, res[2] xxx

Code Overview

This section introduces the code and process description for initialization and corresponding function implementation in the sample.

Note

To use the mode, please turn off Charger auto enable and Battery detection support on the MCUConfig Tool. As shown in Turn Off Charger on the MCUConfig Tool.

Turn Off Charger on the MCUConfig Tool

Source Code Directory

• For project directory, please refer to Source Code Directory.

• Source code directory: sdk\src\sample\io_demo\adc\one-shot\adc_polling_demo.c.

Initialization

The initialization flow for peripherals can refer to Initialization Flow.

The flow of ADC sampling in one shot mode by polling mode is shown in the following figure.

ADC One Shot Sampling by Polling Mode

1. Call Pad_Config() and Pinmux_Config() to initialize the pin.

   static void board_adc_init(void)
   {
      Pad_Config(ADC_1, PAD_SW_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE, PAD_OUT_LOW);
      Pinmux_Config(ADC_1, IDLE_MODE);
   }
   

2. Call RCC_PeriphClockCmd() to enable the ADC clock and function.

3. Initialize the ADC peripheral:

   1. Define the ADC_InitTypeDef type adc_init_struct, and call ADC_StructInit() to pre-fill adc_init_struct with default values.

   2. Modify the adc_init_struct parameters as needed. The ADC initialization parameter configuration is shown in the table below.

   3. Call ADC_Init() to initialize the ADC peripheral.

   ADC Initialization Parameters

   ADC Hardware Parameters	Setting in the adc_init_struct Variables	ADC
   Sample Time	ADC_InitTypeDef::adcClock	ADC_CLK_39K
   Bit Map	ADC_InitTypeDef::bitmap	0x07
   Schedule Index	ADC_InitTypeDef::schIndex	Index 0 is set to EXT_SINGLE_ENDED(1). Index 1 is set to INTERNAL_VBAT_MODE. Index 2 is set to INTERNAL_VADPIN_MODE.

4. Call ADC_INTConfig() to enable ADC one shot mode done interrupt.

5. Call NVIC_Init() to disable NVIC of ADC.

6. Call ADC_Cmd() to enable ADC one shot sampling.

Functional Implementation

When ADC sampling is completed, ADC one shot mode end interrupt status flag is set. The handle flow is shown in ADC One Shot Sampling by Polling Mode.

1. Call ADC_GetIntFlagStatus() to check ADC_INT_ONE_SHOT_DONE interrupt status and wait for the interrupt status flag to be set.

2. Call ADC_ClearINTPendingBit() to clear ADC_INT_ONE_SHOT_DONE interrupt.

3. Call ADC_Cmd() to disable ADC.

4. Call ADC_Read() to read ADC data from schedule table.

5. Call ADC_GetRes() to get conversion result.