# xmpl_trx_txaret.c - Transmitting Frames with TX_ARET

Application Description

The example shows, how a frame is transmitted in TX_ARET mode. Within this mode, CCA is done automatically. Additionally the example illustrates, how the fram data can be directly manipulated in the SRAM (see IRQ service routine).

Code Example

    /* $Id$ */
    /* Example for transmitting frames in tx_aret mode */

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

    static volatile bool tx_in_progress;
    static volatile uint8_t tx_cnt, fail_cnt;

    #define SEQ_OFFSET     (2)
    #define TX_FAIL_OFFSET (7)
    #define TX_SRAM_OFFSET (1)

    int main(void)
    {
    trx_regval_t rval;
    uint8_t txfrm[] = {0x21,0x08,                /* IEEE 802.15.4 FCF:
                                                    data frame with ack request */
                       42,                       /* sequence counter */
                       (PANID & 0xff), (PANID >> 8), /* destination PAN_ID */
                       (SHORT_ADDR & 0xff), (SHORT_ADDR >> 8), /* dest. short address */
                       42,                       /* TX fail counter */
                       'h','e','l','l','o',' ','µ','r','a','c','o','l','i','!', /* data */
                       'X','X'    /* these bytes are overwritten from transceivers
                                   * CRC generator directly 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 */
        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_MS(TRX_INIT_TIME_US);
        rval = trx_bit_read(SR_TRX_STATUS);
        ERR_CHECK(TRX_OFF!=rval);
        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_TX_ARET_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[SEQ_OFFSET] = tx_cnt;
                txfrm[TX_FAIL_OFFSET] = fail_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)
    {
    static volatile trx_regval_t trac_status;

        trac_status = trx_bit_read(SR_TRAC_STATUS);

        tx_in_progress = false;
        if (trac_status != TRAC_SUCCESS)
        {
            fail_cnt++;
        }
        else
        {
            tx_cnt ++;
            LED_CLR(1);
        }
    }
    #else  /* !RFA1 */
    ISR(TRX_IRQ_vect)
    {
    static volatile trx_regval_t irq_cause;
    static volatile trx_regval_t trac_status;

        irq_cause = trx_reg_read(RG_IRQ_STATUS);
        trac_status = trx_bit_read(SR_TRAC_STATUS);

        if (irq_cause & TRX_IRQ_TRX_END)
        {
            tx_in_progress = false;
            if (trac_status != TRAC_SUCCESS)
            {
                fail_cnt++;
            }
            else
            {
                tx_cnt ++;
                LED_CLR(1);
            }
        }
    }
    #endif  /* RFA1 */

    /* EOF */