Mailbox example for FreeRTOS using FreeRTOS demo code as a base

FreeRTOS_Mailbox.c

/**
 * 
 * Adapted from: https://microcontrollerslab.com/create-mailbox-with-queues-using-freertos-arduino/
 * 
 */

#include <stdio.h>
#include <pthread.h>

/* Kernel includes. */
#include "FreeRTOS.h"
#include <queue.h>

// Speed control
#define RECEIVER_TICK_MS 100
#define SENDER_TICK_MS 300
#define SENDER_WAIT_MS 0
#define RECEIVER_MESSAGE_WAIT_MS 10
#define QUEUE_SIZE 3

QueueHandle_t mailbox;

void update_mailbox(void *_)
{
    while (1)
    {
        // Get some sample data, number of ticks so far.
        uint32_t data = xTaskGetTickCount();
        printf("Send: %d\r\n", data);
        if (!xQueueSend(mailbox, &data, SENDER_WAIT_MS))
        {
            printf("Failed to send data, Queue full.\r\n");
        }
        vTaskDelay(pdMS_TO_TICKS(SENDER_TICK_MS));
    }
}

void read_mailbox(void *_)
{
    while (1)
    {
        uint32_t data = 0;
        printf("Starting to read Mailbox...\r\n");
        fflush(stdout);
        // Read an item from the mailbox and wait for RECEIVER_MESSAGE_WAIT_MS ticks max.
        if (xQueueReceive(mailbox, &data, pdMS_TO_TICKS(RECEIVER_MESSAGE_WAIT_MS)))
        {
            // Received an item from mailbox.
            printf("Received: %d\r\n", data);
        }
        else
        {
            printf("Item not yet available\r\n");
        }
        vTaskDelay(pdMS_TO_TICKS(RECEIVER_TICK_MS));
    }
}

void main_mailbox()
{
    // Mailbox that fits for QUEUE_SIZE ints
    mailbox = xQueueCreate(QUEUE_SIZE, sizeof(uint32_t));
    xTaskCreate(update_mailbox, "Sender", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(read_mailbox, "Receiver", configMINIMAL_STACK_SIZE, NULL, 1, NULL);

    vTaskStartScheduler();

    for (;;)
        ;
}