ADC DMA Driver

The Analog to Digital Converter (ADC) DMA driver uses DMA system to transfer data from ADC to a memory buffer in RAM. User must configure DMAC system driver accordingly. To set memory buffer and its size adc_dma_read function is used. This function programs DMA to transfer the results of input signal conversion to the given buffer. A callback is called when all the data is transfered, if it is registered via adc_dma_register_callback function.

Summary of the API's Functional Features

The API provides functions to:

Initialize and deinitialize the driver and associated hardware
Select single shot or free running conversion modes
Configure major ADC properties such as resolution and reference source
Notification via callback about errors and transfer completion

Summary of Configuration Options

Below is a list of the main ADC parameters that can be configured in START. Many of these parameters are used by the adc_dma_init function when initializing the driver and underlying hardware. Most of the initial values can be overridden and changed runtime by calling the appropriate API functions, such as adc_dma_set_resolution.

Selecting which ADC input channels to enable for positive and negative input
Which clock source and prescaler the ADC uses
Various aspects of Event control
Single shot or free running conversion modes
Sampling properties such as resolution, window mode, and reference source
Run in Standby or Debug mode

DMA is a system driver in START and can be enabled and configured there.

Driver Implementation Description

Dependencies

ADC hardware with result ready/conversion done and error interrupts

Example of Usage

The following shows a simple example of using the DMA to transfer ADC results into RAM buffer. User must configure DMAC system driver accordingly in START.

The ADC must have been initialized by adc_dma_init. This initialization will configure the operation of the ADC, such as resolution and reference source, etc.

          /* The buffer size for ADC */
          #define ADC_0_BUFFER_SIZE 16
          static uint8_t ADC_0_buffer[ADC_0_BUFFER_SIZE];
          static void convert_cb_ADC_0(const struct adc_dma_descriptor *const descr)
          {
          }
          /**
           * Example of using ADC_0 to generate waveform.
           */
          void ADC_0_example(void)
          {
              adc_dma_register_callback(&ADC_0, ADC_DMA_COMPLETE_CB, convert_cb_ADC_0);
              adc_dma_enable_channel(&ADC_0, 0);
              adc_dma_read(&ADC_0, ADC_0_buffer, ADC_0_BUFFER_SIZE);
          }