ADC GDMA Mode

This sample code guide is designed to help users easily and comprehensively understand ADC sample. This sample demonstrates how ADC samples data in continuous mode by GDMA. This sample uses continuous mode of the ADC peripheral to measure voltage on P0_0 and P0_1.

Requirements

For hardware requirements, please refer to the Requirements.

Wiring

Connect P0_0 and P0_1 of EVB to external DC voltage source. Input voltage of P0_0 and P0_1 must range from 0 to 3.3V.

Configurations

1. 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_gdma_demo();
   

Building and Downloading

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

Experimental Verification

Press the Reset button on the EVB, ADC starts continuous sampling, and sample rawdata will be stored in array ADC_Buffer.

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\gdma\adc_dma\adc_gdma_demo.c.

ADC Initialization

The initialization flow for peripherals can refer to Initialization Flow.

ADC continuous mode initialization flow is shown in the following figure.

ADC Continuous Mode Initialization Flow Chart

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

   static void board_adc_init(void)
   {
      Pad_Config(ADC_0, PAD_SW_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE, PAD_OUT_LOW);
      Pad_Config(ADC_1, PAD_SW_MODE, PAD_IS_PWRON, PAD_PULL_NONE, PAD_OUT_DISABLE, PAD_OUT_LOW);
      Pinmux_Config(ADC_0, IDLE_MODE);
      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 adcInitStruct, and call ADC_StructInit() to pre-fill adcInitStruct with default values.

   2. Modify the adcInitStruct 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 adcInitStruct Variables	ADC
   Bit Map	ADC_InitTypeDef::bitmap	0x03
   Schedule Index	ADC_InitTypeDef::schIndex	Index 0 is set to EXT_SINGLE_ENDED(0). Index 1 is set to EXT_SINGLE_ENDED(1).
   Burst Size	ADC_InitTypeDef::adcBurstSize	1
   Sample Time	ADC_InitTypeDef::adcClock	ADC_CLK_39K
   FIFO Threshold Level	ADC_InitTypeDef::adcFifoThd	5

4. Call ADC_INTConfig() to enable ADC FIFO read error interrupt ADC_INT_FIFO_RD_ERR.

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

GDMA Initialization

GDMA initialization flow is shown in the following figure.

GDMA Initialization Flow Chart

1. Call RCC_PeriphClockCmd() to enable the GDMA clock and function.

2. Call GDMA_channel_request to request an unused GDMA channel.

3. Initialize the GDMA peripheral:

   1. Define the GDMA_InitTypeDef type GDMA_InitStruct, and call GDMA_StructInit() to pre-fill GDMA_InitStruct with default values.

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

   3. Call GDMA_Init() to initialize the GDMA peripheral.

   GDMA Initialization Parameters

   GDMA Hardware Parameters	Setting in the GDMA_InitStruct Variables	GDMA
   Channel Num	GDMA_InitTypeDef::GDMA_ChannelNum	ADC_DMA_CHANNEL_NUM
   Transfer Direction	GDMA_InitTypeDef::GDMA_DIR	GDMA_DIR_PeripheralToMemory
   Buffer Size	GDMA_InitTypeDef::GDMA_BufferSize	200
   Source Address Increment or Fix	GDMA_InitTypeDef::GDMA_SourceInc	DMA_SourceInc_Fix
   Destination Address Increment or Fix	GDMA_InitTypeDef::GDMA_DestinationInc	DMA_DestinationInc_Inc
   Source Data Size	GDMA_InitTypeDef::GDMA_SourceDataSize	GDMA_DataSize_HalfWord
   Destination Data Size	GDMA_InitTypeDef::GDMA_DestinationDataSize	GDMA_DataSize_HalfWord
   Source Burst Transaction Length	GDMA_InitTypeDef::GDMA_SourceMsize	GDMA_Msize_1
   Destination Burst Transaction Length	GDMA_InitTypeDef::GDMA_DestinationMsize	GDMA_Msize_1
   Source Address	GDMA_InitTypeDef::GDMA_SourceAddr	(uint32_t)(&(ADC->FIFO))
   Destination Address	GDMA_InitTypeDef::GDMA_DestinationAddr	(uint32_t)ADC_Buffer
   Source Handshake	GDMA_InitTypeDef::GDMA_SourceHandshake	GDMA_Handshake_ADC

4. Call NVIC_Init() to enable NVIC of GDMA.

5. Call GDMA_INTConfig() to enable GDMA transfer complete interrupt GDMA_INT_Transfer.

Functional Implementation

Enable ADC Contiunous Sampling

1. Call GDMA_Cmd() to enable GDMA.

2. Call ADC_Cmd() to enable ADC contiunous sampling.

ADC Interrupt Handle

When read the empty FIFO, ADC FIFO read error interrupt is triggered:

1. Call ADC_GetIntFlagStatus() to check ADC_INT_FIFO_RD_ERR interrupt status flag.

2. Call ADC_ClearINTPendingBit() to clear ADC_INT_FIFO_RD_ERR interrupt.

GDMA Interrupt Handle

When GDMA transfer is completed, transfer complete interrupt is triggered:

1. Call GDMA_ClearINTPendingBit() to clear GDMA_INT_Transfer interrupt.

2. Call ADC_Cmd() to disable ADC.

3. Call GDMA_channel_release() to release the GDMA channel used by ADC.