Continuous Mode

The example performs voltage detection by using the ADC in continuous sampling mode.

The example also includes configurable macros ADC_CONFIG_GDMA_MODE_EN to control whether DMA is used for data handling.

If DMA handling is not enabled, the ADC_INT_FIFO_THD interrupt is triggered after ADC sampling is complete, and within the interrupt function, raw data is read and voltage conversion calculations are performed.

If DMA handling is enabled, DMA handles the data from ADC FIFO to the array and triggers the GDMA_INT_Transfer interrupt when the transfer is complete.

Requirements

The sample supports the following development kits:

Development Kits

Hardware Platforms

Board Name

RTL87x2G HDK

RTL87x2G EVB

For more requirements, please refer to Quick Start.

Wiring

Connect P2_4 to external voltage input.

Configurations

The example configurable macros are as follows:

  1. ADC_CONFIG_GDMA_MODE_EN ：select whether or not to use DMA for ADC sample data handling, 1 indicates that DMA handling is used, 0 indicates that DMA handling is not used.

  2. ADC_MODE_DIVIDE_OR_BYPASS : selects the voltage sampling range of the ADC, and the selectable values are as follows:

    • ADC_DIVIDE_MODE ：In Divide Mode, the ADC samples voltage values ranging from 0 to 3.3V

    • ADC_BYPASS_MODE ：In Bypass Mode, the ADC samples voltage values ranging from 0 to 0.9V

Building and Downloading

This sample can be found in the SDK folder:

Project file: samples\peripheral\adc\continuous_gdma\proj\rtl87x2g\mdk

Project file: samples\peripheral\adc\continuous_gdma\proj\rtl87x2g\gcc

To build and run the sample, follow the steps listed below:

  1. Open sample project file.

  2. To build the target, follow the steps listed on the Generating App Image in Quick Start.

  3. After a successful compilation, the app bin app_MP_xxx.bin will be generated in the directory mdk\bin or gcc\bin.

  4. To download app bin into EVB board, follow the steps listed on the MP Tool Download in Quick Start.

  5. Press reset button on EVB board and it will start running.

Experimental Verification

  1. When the EVB starts, observe the following log within the Debug Analyzer.

    Start ADC Continuous Mode test !

  2. ADC Configurations:

    1. If the ADC is configured as ADC_DIVIDE_MODE , print the following log.

      [ADC]ADC sample mode is divide mode !

    2. If the ADC is configured as ADC_BYPASS_MODE , print the following log.

      [ADC]ADC sample mode is bypass mode !

  3. After the ADC sampling is finished, the raw data collected and the converted voltage value will be printed in the Debug Analyzer. If the macro ADC_CONFIG_GDMA_MODE_EN is enabled, DMA interrupt information will be printed; if the macro ADC_CONFIG_GDMA_MODE_EN is not enabled, ADC interrupt information will be printed.

    [io_adc]io_adc_voltage_calculate: ADC rawdata_0 = xxx, voltage_0 = xxxmV
[io_adc]io_adc_voltage_calculate: ADC rawdata_1 = xxx, voltage_1 = xxxmV
...

Code Overview

This chapter will be introduced according to the following several parts:

  1. Source Code Directory.

  2. Peripheral initialization will be introduced in chapter Initialization .

  3. Functional implementation after initialization will be introduced in chapter Functional Implementation .

Source Code Directory

  • Project Directory: sdk\samples\peripheral\adc\continuous_gdma\proj

  • Source Code Directory: sdk\samples\peripheral\adc\continuous_gdma\src

Source files are currently categorized into several groups as below.

└── Project: continuous_gdma
    └── secure_only_app
        └── Device                   includes startup code
            ├── startup_rtl.c
            └── system_rtl.c
        ├── CMSIS                    includes CMSIS header files
        ├── CMSE Library             Non-secure callable lib
        ├── Lib                      includes all binary symbol files that user application is built on
            └── rtl87x2g_io.lib
        ├── Peripheral               includes all peripheral drivers and module code used by the application
            ├── rtl_rcc.c
            ├── rtl_pinmux.c
            ├── rtl_gdma.c
            └── rtl_adc.c
        └── APP                      includes the ble_peripheral user application implementation
            ├── main_ns.c
            └── io_adc.c

Initialization

The initialization process includes global_adc_init, board_adc_init, and driver_adc_init If the macro ADC_CONFIG_GDMA_MODE_EN is enabled, the initialization process should also include driver_gdma_adc_init

global_adc_init contains the global settings.

  1. Execute ADC_CalibrationInit() for ADC FT calibration.

  2. Initialize the receive buffer ADC_Recv_Buffer.

board_adc_init contains the PAD settings.

  1. Set pin as SW mode, PowerOn, internal Pull-None, disable output, output low level.

driver_adc_init contains the initialization of ADC peripheral.

  1. Enable PCC clock.

  2. Config ADC sample channel, channel 0 of the ADC selects pin P2_4 of the ADC single-ended mode, the corresponding bitmap is 0x01.

  3. If the macro ADC_CONFIG_GDMA_MODE_EN is enabled, it should config ADC_WaterLevel.

  4. Set ADC_DataWriteToFifo to ENABLE, Set ADC_FifoThdLevel.

  5. If configured as bypass mode, execute ADC_BypassCmd() to enable the high resistance mode of the corresponding channel.

  6. Config ADC interrupt.

RCC_PeriphClockCmd(APBPeriph_ADC, APBPeriph_ADC_CLOCK, ENABLE);
...
#if ADC_CONFIG_GDMA_MODE_EN
  ADC_InitStruct.ADC_WaterLevel       = 4;
#endif
  ADC_InitStruct.ADC_DataWriteToFifo  = ENABLE;
  ...
#if ADC_CONFIG_GDMA_MODE_EN
  ADC_INTConfig(ADC, ADC_INT_FIFO_RD_ERR, ENABLE);
  ADC_INTConfig(ADC, ADC_INT_FIFO_OVERFLOW, ENABLE);
#else
  ADC_INTConfig(ADC, ADC_INT_FIFO_THD, ENABLE);
#endif

Note

In ADC Continuous mode, data is stored in the ADC FIFO by default.

driver_gdma_adc_init contains the initialization of the GDMA peripheral.

  1. GDMA transfer direction is peripheral to memory transfer.

  2. Source address is set to ADC FIFO, destination address is set to ADC_Recv_Buffer .

  3. Set source address to fixed and destination address to increase.

  4. Enable transmission completion interrupt GDMA_INT_Transfer .

GDMA_InitStruct.GDMA_DIR                = GDMA_DIR_PeripheralToMemory;
GDMA_InitStruct.GDMA_SourceInc          = DMA_SourceInc_Fix;
GDMA_InitStruct.GDMA_DestinationInc     = DMA_DestinationInc_Inc;
GDMA_InitStruct.GDMA_SourceAddr         = (uint32_t)(&(ADC->ADC_FIFO_READ));
GDMA_InitStruct.GDMA_DestinationAddr    = (uint32_t)ADC_Recv_Buffer;
...
GDMA_INTConfig(ADC_GDMA_CHANNEL_NUM, GDMA_INT_Transfer, ENABLE);
...

Functional Implementation

  1. If enabling the macro ADC_CONFIG_GDMA_MODE_EN, execute GDMA_Cmd() after initializing GDMA.

  2. Execute ADC_ClearFIFO() before ADC sampling to clear data in ADC FIFO.

  3. Execute ADC_Cmd(), start ADC sampling.

  4. If enabling the macro ADC_CONFIG_GDMA_MODE_EN, when the GDMA has finished handling the data, the GDMA_INT_Transfer interrupt is triggered, and the ADC_GDMA_Channel_Handler function is executed.

    1. Disable ADC continuous sampling mode.

    2. Read ADC sample data. (Refer to 6)

    3. Reset the GDMA information, including source address, destination address, and carry length.

    4. Enable GDMA transfer, clear ADC FIFO, and enable ADC conversion.

void ADC_GDMA_Channel_Handler(void)
{
    ADC_Cmd(ADC, ADC_CONTINUOUS_MODE, DISABLE);
    for (uint32_t i = 0; i < GDMA_TRANSFER_SIZE; i++)
    {
      ...
    }
    GDMA_SetSourceAddress(ADC_GDMA_Channel, (uint32_t)(&(ADC->ADC_FIFO_READ)));
    GDMA_SetDestinationAddress(ADC_GDMA_Channel, (uint32_t)(ADC_Recv_Buffer));
    GDMA_SetBufferSize(ADC_GDMA_Channel, GDMA_TRANSFER_SIZE);
    GDMA_ClearINTPendingBit(ADC_GDMA_CHANNEL_NUM, GDMA_INT_Transfer);
    GDMA_Cmd(ADC_GDMA_CHANNEL_NUM, ENABLE);

    ADC_ClearFIFO(ADC);
    ADC_Cmd(ADC, ADC_CONTINUOUS_MODE, ENABLE);
}

  1. If not enabling the macro ADC_CONFIG_GDMA_MODE_EN, when the number of ADC FIFO exceeds the threshold value, trigger the ADC_INT_FIFO_THD interrupt and enter the interrupt handler function.

    1. Execute ADC_GetFIFODataLen() to read FIFO data length, execute ADC_ReadFIFOData() to read ADC FIFO data.

    2. Execute ADC_ClearFIFO() to clear ADC FIFO data.

    3. Execute ADC_GetVoltage() to calculate the sample voltage based on the sample data.

if (ADC_GetINTStatus(ADC, ADC_INT_FIFO_THD) == SET)
{
    ADC_Cmd(ADC, ADC_CONTINUOUS_MODE, DISABLE);
    data_len = ADC_GetFIFODataLen(ADC);
    ADC_ReadFIFOData(ADC, sample_data, data_len);

    ADC_ClearFIFO(ADC);
    ...
    ADC_Cmd(ADC, ADC_CONTINUOUS_MODE, ENABLE);
}

Note

When ADC FIFO overflow triggers ADC_INT_FIFO_OVERFLOW interrupt, enter the interrupt handling function SAR_ADC_Handler , and clear ADC FIFO data.

Troubleshooting

  1. If the IC obtained has not been verified by FT, the ADC will not be able to convert to the correct voltage value. The following message will be printed within the log tool.

    [ADC]ADC_CalibrationInit fail!

  2. If the ADC sample value is incorrect, print the error status.

    [ADC]adc_sample_demo: ADC parameter or efuse data error! i = xxx, error_status = xxx