Quick Start Guide for Debug Print Service for FreeRTOS

In this use case, the Debug Print service is configured with the following settings:

• 128-byte print buffer
• output via the SERCOM UART connected to Embedded Debugger (EDBG) on an Xplained Pro board
• 9600 baud transfer rate

A FreeRTOS task is created which every second prints a constant string and a string containing an incrementing 32-bit hexadecimal integer.

Setup

Prerequisites

FreeRTOS must be added to the project, and the clock driver must be configured to initialize GCLK 0 to 48 MHz. Note that FreeRTOS also has a setting for the system clock frequency which must be updated.

Code

The following must be added to the file conf_dbg_print.h:

#include <board.h>

#define CONF_DBG_PRINT_BUFFER_SIZE   128

#define CONF_DBG_PRINT_SERCOM        EDBG_CDC_MODULE
#define CONF_DBG_PRINT_GCLK_SOURCE   GCLK_GENERATOR_0
// #define CONF_DBG_PRINT_BAUD_RATE     9600
// This BAUD value gives 9600 baud with 48 MHz GCLK
#define CONF_DBG_PRINT_BAUD_VALUE    65326

#define CONF_DBG_PRINT_SERCOM_MUX    EDBG_CDC_SERCOM_MUX_SETTING
#define CONF_DBG_PRINT_PINMUX_PAD0   EDBG_CDC_SERCOM_PINMUX_PAD0
#define CONF_DBG_PRINT_PINMUX_PAD1   EDBG_CDC_SERCOM_PINMUX_PAD1
#define CONF_DBG_PRINT_PINMUX_PAD2   EDBG_CDC_SERCOM_PINMUX_PAD2
#define CONF_DBG_PRINT_PINMUX_PAD3   EDBG_CDC_SERCOM_PINMUX_PAD3

Workflow

1. Include board definition to get settings for output to EDBG:

   #include <board.h>

2. Set buffer size to 128 byte:

   #define CONF_DBG_PRINT_BUFFER_SIZE   128

3. Use SERCOM connected to EDBG CDC for output at 9600 baud:

   #define CONF_DBG_PRINT_SERCOM        EDBG_CDC_MODULE
   #define CONF_DBG_PRINT_GCLK_SOURCE   GCLK_GENERATOR_0
   // #define CONF_DBG_PRINT_BAUD_RATE     9600
   // This BAUD value gives 9600 baud with 48 MHz GCLK
   #define CONF_DBG_PRINT_BAUD_VALUE    65326
   
   #define CONF_DBG_PRINT_SERCOM_MUX    EDBG_CDC_SERCOM_MUX_SETTING
   #define CONF_DBG_PRINT_PINMUX_PAD0   EDBG_CDC_SERCOM_PINMUX_PAD0
   #define CONF_DBG_PRINT_PINMUX_PAD1   EDBG_CDC_SERCOM_PINMUX_PAD1
   #define CONF_DBG_PRINT_PINMUX_PAD2   EDBG_CDC_SERCOM_PINMUX_PAD2
   #define CONF_DBG_PRINT_PINMUX_PAD3   EDBG_CDC_SERCOM_PINMUX_PAD3

Use Case

Code

Add the following to your main application C file:

uint32_t main_counter;
char main_string[] = "Main task iteration: 0x00000000\r\n";

static void main_task(void *params)
{
    do {
        dbg_print_str("Main task loop executing\r\n");

        // Update hexadecimal 32-bit integer in string, and print it
        dbg_sprint_hexint(&main_string[23], main_counter++);
        dbg_print_str(main_string);

        vTaskDelay(1000 / portTICK_RATE_MS);
    } while(1);
}

Add the following to your application's main() function:

    system_init();
    dbg_init();

    xTaskCreate(&main_task,
        (const char *)"Main task",
        configMINIMAL_STACK_SIZE + 100,
        NULL,
        tskIDLE_PRIORITY + 2,
        NULL);

    vTaskStartScheduler();

Workflow

1. Define debug variables to print out:

   uint32_t main_counter;
   char main_string[] = "Main task iteration: 0x00000000\r\n";

2. Define a FreeRTOS task for printing debug data forever:

   static void main_task(void *params)
   {
       do {

3. Print a constant string at the start of the task-loop:

           dbg_print_str("Main task loop executing\r\n");

4. Write a hexadecimal integer into a string and print it:

           // Update hexadecimal 32-bit integer in string, and print it
           dbg_sprint_hexint(&main_string[23], main_counter++);
           dbg_print_str(main_string);

   Note

   dbg_sprint_hexint() does not write the 0x prefix, only the hexadecimal digits.

5. Add a 1 sec delay at the of the task-loop and close the task definition:

           vTaskDelay(1000 / portTICK_RATE_MS);
       } while(1);
   }

6. In main(), initialize the system and debug print service:

       system_init();
       dbg_init();

7. Create an instance of the debug printing task:

       xTaskCreate(&main_task,
           (const char *)"Main task",
           configMINIMAL_STACK_SIZE + 100,
           NULL,
           tskIDLE_PRIORITY + 2,
           NULL);

8. Start the FreeRTOS scheduler:

       vTaskStartScheduler();