CMSIS Example - Mail and Timer

    #include <stdint.h>

    #include "bsp-fifisdr.h"

    #include "lpclib.h"
    #include "task-gui.h"

    #define GUI_QUEUE_LENGTH                        (4)

    typedef struct {
        uint8_t opcode;
    } GUI_Message;

    /** Message opcodes for GUI task. */
    enum {
        GUI_OPCODE_LED_TICK,
    };

    /** Identifiers for OS timers. */
    enum {
        GUI_TIMERMAGIC_LED,
    };

    /** Local task context. */
    static struct {
        osMailQId queue;
        osTimerId ledTick;
        int led;
    } gui;

    static void GUI_osalCallback (void const *pArgument)
    {
        (void) pArgument;

        if (gui.queue == NULL) {
            return;
        }

        GUI_Message *pMessage = osMailAlloc(gui.queue, );

        if (pMessage == NULL) {
            return;
        }

        pMessage->opcode = GUI_OPCODE_LED_TICK;
        osMailPut(gui.queue, pMessage);
    }

    osMailQDef(guiQueue, GUI_QUEUE_LENGTH, GUI_Message);
    osTimerDef(led, GUI_osalCallback);

    void GUI_task (const void *pArgs)
    {
        (void) pArgs;
        GUI_Message *pMessage;
        osEvent event;

        gui.queue = osMailCreate(osMailQ(guiQueue), NULL);

        gui.ledTick = osTimerCreate(osTimer(led), osTimerPeriodic, (void *)GUI_TIMERMAGIC_LED);
        osTimerStart(gui.ledTick, );

        while () {
            /* Is there a new message? */
            event = osMailGet(gui.queue, osWaitForever);
            if (event.status == osEventMail) {
                pMessage = (GUI_Message *)event.value.p;
                switch (pMessage->opcode) {
                case GUI_OPCODE_LED_TICK:
                    gui.led = gui.led ^ ;
                    BSP_setLed(gui.led);
                    break;
                }

                osMailFree(gui.queue, pMessage);
            }
        }
    }