src/part2/examples/local/rf/tests/listen.c

/*
 *  ======== listen.c ========
 */
#include <xdc/runtime/System.h>
#include <local/rf/Radio.h>
#include <local/rf/Bsp.h>
#include <local/rf/Atomic.h>

static          uint8_t  sRxTid = 0;
static          Radio_LinkId sLinkID2;
static volatile uint8_t  sSemaphore = 0;

static void     linkFrom(void);
static uint8_t  sRxCallback(Radio_LinkId);  /* UART Rx callback handler */

/*
 *  ======== main ========
 */
void main(void)
{
    Radio_Addr lAddr = {0x78, 0x56, 0x34, 0x12};

    /* If an on-the-fly device address is generated it must be done before the
     * call to Radio_start(). If the address is set here the ROM value will not
     * be used. 
     *
     * This call will fail because the join will fail since there is no
     * Access Point in this scenario. But we don't care -- just use the
     * default link token later.
     *
     * We supply a callback pointer to handle the message returned by the peer.
     */
    Radio_start(sRxCallback, &lAddr);
    
    /* turn on LEDs. */
    if (!Bsp_led(2)) {
        Bsp_toggleLed(2);
    }
    if (!Bsp_led(1)) {
        Bsp_toggleLed(1);
    }
    
    /* wait for a button press... */
    for (;;) {
        Atomic_clear8((Int8 *)&sSemaphore);
        if (Bsp_button(1) || Bsp_button(2)) {
            break;
        }
    }
    
    /* never coming back... */
    linkFrom();
    
    /* but in case we do... */
    System_abort("returned from linkFrom()!\n");
}

/*
 *  ======== linkFrom ========
 */
static void linkFrom()
{
    uint8_t msg[2], tid = 0;
    
    /* Turn off one LED so we can tell the device is now listening.
     * Received messages will toggle the other LED.
     */
    Bsp_toggleLed(1);
    
    /* listen for link forever... */
    while (1) {
        if (Radio_SUCCESS == Radio_listen(&sLinkID2)) {
            break;
        }
        /* Implement fail-to-link policy here. otherwise, listen again. */
    }
    
    /* turn on LED1 on the peer in response to receiving a frame. */
    msg[0] = 0x01;
    
    /* turn on RX. default is RX off. */
    Radio_setRxOn();
    
    while (1) {
        /* Wait for a frame to be received. The Rx handler, which is running
         * in ISR thread, posts this semaphore allowing the application to
         * send the reply message in the user thread.
         */
        if (sSemaphore) {
            msg[1] = ++tid;
            Radio_send(sLinkID2, msg, sizeof(msg));
        
            /* Reset semaphore. This is not properly protected and there is a
             * race here. In theory we could miss a message. Good enough for
             * a demo, though.
             */
            Atomic_clear8((Int8 *)&sSemaphore);
        }
    }
}

/*
 *  ======== sRxCallback ========
 *  handle received messages
 */
static uint8_t sRxCallback(Radio_LinkId port)
{
    uint8_t msg[2], len, tid;
    
    /* is the callback for the link ID we want to handle? */
    if (port == sLinkID2) {
        /* yes. go get the frame. we know this call will succeed. */
        if ((Radio_SUCCESS == Radio_receive(sLinkID2, msg, &len)) && len) {
            /* Check the application sequence number to detect
             * late or missing frames...
             */
            tid = msg[1];
            if (tid) {
                if (tid > sRxTid) {
                    /* we're good. toggle LED */
                    Bsp_toggleLed(msg[0]);
                    sRxTid = tid;
                }
            }
            else {
                /* wrap case... */
                if (sRxTid) {
                    /* we're good. toggle LED */
                    Bsp_toggleLed(msg[0]);
                    sRxTid = tid;
                }
            }

            /* Post to the semaphore to let application know so it sends
             * the reply
             */
            sSemaphore = 1;

            /* drop frame. we're done with it. */
            return (1);
        }
    }

    /* keep frame for later handling */
    return (0);
}