Quick Start Guide for SDADC - Callback

In this use case, the SDADC will convert 128 samples using interrupt driven conversion.

When all samples have been sampled, a callback will be called that signals the main application that conversion is compete.

The SDADC will be set up as follows:

• GCLK generator 0 (GCLK main) clock source
• Internal bandgap reference 1V
• Div 2 clock prescaler
• Over Sampling Ratio is 1024
• Skip 2 samples
• MUX input on SDADC AIN2
• All events (input and generation) disabled
• Free running disabled
• Run in standby disabled
• On command disabled
• Disable all positive input in sequence
• Window monitor disabled
• No gain/offset/shift correction

Setup

Prerequisites

There are no special setup requirements for this use-case.

Code

Add to the main application source file, outside of any functions:

struct sdadc_module sdadc_instance;

#define SDADC_SAMPLES 128
int32_t sdadc_result_buffer[SDADC_SAMPLES];

Callback function:

volatile bool sdadc_read_done = false;

void sdadc_complete_callback(
        const struct sdadc_module *const module)
{
    sdadc_read_done = true;
}

Copy-paste the following setup code to your user application:

void configure_sdadc(void)
{
    struct sdadc_config config_sdadc;
    sdadc_get_config_defaults(&config_sdadc);

    config_sdadc.clock_prescaler = 2;
    config_sdadc.reference.ref_sel = SDADC_REFERENCE_INTREF;
    config_sdadc.osr             = SDADC_OVER_SAMPLING_RATIO1024;
    config_sdadc.mux_input       = SDADC_MUX_INPUT_AIN2;

    sdadc_init(&sdadc_instance, SDADC, &config_sdadc);

    sdadc_enable(&sdadc_instance);
}

void configure_sdadc_callbacks(void)
{
    sdadc_register_callback(&sdadc_instance,
            sdadc_complete_callback, SDADC_CALLBACK_READ_BUFFER);
    sdadc_enable_callback(&sdadc_instance, SDADC_CALLBACK_READ_BUFFER);
}

Add to user application initialization (typically the start of main()):

    configure_sdadc();
    configure_sdadc_callbacks();

Workflow

1. Create a module software instance structure for the SDADC module to store the SDADC driver state while it is in use.

   struct sdadc_module sdadc_instance;

   Note

   This should never go out of scope as long as the module is in use. In most cases, this should be global.

2. Create a buffer for the SDADC samples to be stored in by the driver asynchronously.

   #define SDADC_SAMPLES 128
   int32_t sdadc_result_buffer[SDADC_SAMPLES];

3. Create a callback function that will be called each time the SDADC completes an asynchronous read job.

   volatile bool sdadc_read_done = false;
   
   void sdadc_complete_callback(
           const struct sdadc_module *const module)
   {
       sdadc_read_done = true;
   }

4. Configure the SDADC module.
   • Create a SDADC module configuration struct, which can be filled out to adjust the configuration of a physical SDADC peripheral.

         struct sdadc_config config_sdadc;

   • Initialize the SDADC configuration struct with the module's default values.

         sdadc_get_config_defaults(&config_sdadc);

     Note

     This should always be performed before using the configuration struct to ensure that all values are initialized to known default settings.

   • Change the SDADC module configuration to suit the application.

         config_sdadc.clock_prescaler = 2;
         config_sdadc.reference.ref_sel = SDADC_REFERENCE_INTREF;
         config_sdadc.osr             = SDADC_OVER_SAMPLING_RATIO1024;
         config_sdadc.mux_input       = SDADC_MUX_INPUT_AIN2;

   • Set SDADC configurations.

         sdadc_init(&sdadc_instance, SDADC, &config_sdadc);

   • Enable the SDADC module so that conversions can be made.

         sdadc_enable(&sdadc_instance);

5. Register and enable the SDADC read buffer complete callback handler.
   • Register the user-provided read buffer complete callback function with the driver, so that it will be run when an asynchronous buffer read job completes.

         sdadc_register_callback(&sdadc_instance,
                 sdadc_complete_callback, SDADC_CALLBACK_READ_BUFFER);

   • Enable the read buffer complete callback so that it will generate callbacks.

         sdadc_enable_callback(&sdadc_instance, SDADC_CALLBACK_READ_BUFFER);

Use Case

Code

Copy-paste the following code to your user application:

    system_interrupt_enable_global();

    sdadc_read_buffer_job(&sdadc_instance, sdadc_result_buffer, SDADC_SAMPLES);

    while (sdadc_read_done == false) {
        /* Wait for asynchronous SDADC read to complete */
    }

    while (1) {
        /* Infinite loop */
    }

Workflow

• Enable global interrupts, so that callbacks can be generated by the driver.

      system_interrupt_enable_global();

• Start an asynchronous SDADC conversion, to store SDADC samples into the global buffer and generate a callback when complete.

      sdadc_read_buffer_job(&sdadc_instance, sdadc_result_buffer, SDADC_SAMPLES);

• Wait until the asynchronous conversion is complete.

      while (sdadc_read_done == false) {
          /* Wait for asynchronous SDADC read to complete */
      }

• Enter an infinite loop once the conversion is complete.

      while (1) {
          /* Infinite loop */
      }