# xmpl_trx_tx.c - Transmitting Frames

The next example shows, how a frame is transmitted.

    /* $Id: xmpl_trx_tx.c,v 1.5 2009/12/22 16:47:10 joerg_wunsch Exp $ */
    /* Example for transmitting frames */

    #include "board.h"
    #include "transceiver.h"
    #include "ioutil.h"
    #include "xmpl.h"

    static volatile bool tx_in_progress;
    static volatile uint8_t tx_cnt;

    int main(void)
    {
    trx_regval_t rval;
    uint8_t txfrm[] = {1,0, /* faked ieee 802.15.4 data frame control field
                             * this is just needed, that a sniffer has to display something.*/
                       42,  /* sequence counter, updated by software */
                      'h','e','l','l','o',' ','µ','r','a','c','o','l','i','!', /* data */
                      'X','X' /* these bytes are overwritten from transceivers CRC generator just before sent. */
                      };
        /* This will stop the application before initializing the radio transceiver
         * (ISP issue with MISO pin, see FAQ)
         */
        trap_if_key_pressed();

        /* Step 0: init MCU peripherals */
        LED_INIT();
        trx_io_init(SPI_RATE_1_2);
        LED_SET_VALUE(LED_MAX_VALUE);
        LED_SET_VALUE(0);

        /* Step 1: initialize the transceiver */
        DELAY_US(TRX_INIT_TIME_US);
        TRX_RESET_LOW();
        TRX_SLPTR_LOW();
        DELAY_US(TRX_RESET_TIME_US);
        TRX_RESET_HIGH();
        trx_reg_write(RG_TRX_STATE,CMD_TRX_OFF);
        DELAY_US(TRX_INIT_TIME_US);
        rval = trx_bit_read(SR_TRX_STATUS);
        ERR_CHECK_DIAG(TRX_OFF!=rval,1);
        LED_SET_VALUE(1);

        /* Step 2: setup transmitter
         * - configure radio channel
         * - enable transmitters automatic crc16 generation
         * - go into TX state,
         * - enable "transmit end" IRQ
         */
        trx_bit_write(SR_CHANNEL,CHANNEL);
        trx_bit_write(SR_TX_AUTO_CRC_ON,1);
        trx_reg_write(RG_TRX_STATE,CMD_PLL_ON);
    #if defined(TRX_IRQ_TRX_END)
        trx_reg_write(RG_IRQ_MASK,TRX_IRQ_TRX_END);
    #elif defined(TRX_IRQ_TX_END)
        trx_reg_write(RG_IRQ_MASK,TRX_IRQ_TX_END);
    #else
    #  error "Unknown IRQ bits"
    #endif
        sei();
        LED_SET_VALUE(2);

        /* Step 3: send a frame each 500ms */
        tx_cnt = 0;
        tx_in_progress = false;
        LED_SET_VALUE(0);

        while(1)
        {
            WAIT500MS();
            if (tx_in_progress == false)
            {
                txfrm[2] = tx_cnt;
                trx_frame_write (sizeof(txfrm), txfrm);
                tx_in_progress = true;
                TRX_SLPTR_HIGH();
                TRX_SLPTR_LOW();
                LED_SET(1);
                LED_TOGGLE(0);
            }
        }
    }

    #if defined(TRX_IF_RFA1)
    ISR(TRX24_TX_END_vect)
    {
        /* transmission completed */
        tx_in_progress = false;
        tx_cnt ++;
        LED_CLR(1);
    }
    #else  /* !RFA1 */
    ISR(TRX_IRQ_vect)
    {
    static volatile trx_regval_t irq_cause;
        irq_cause = trx_reg_read(RG_IRQ_STATUS);
        if (irq_cause & TRX_IRQ_TRX_END)
        {
            /* transmission completed */
            tx_in_progress = false;
            tx_cnt ++;
            LED_CLR(1);
        }
    }
    #endif

    /* EOF */