xmpl_linbuf_tx.c - Using Linear Buffers for Data Transmission

Application Description

The application fills a piece of text as chunks in a linear buffer and sends it. The example illustrates

• the initialization of a linear buffer (see Buffer Managment),
• the appending of characters as payload,
• the prepending of a frame header prior the payload,
• the extraction of data pointer and data size from the buffer.
• reset of the buffer.

Code Example

/* $Id: pgXmplLbufferTx.html,v 1.1.1.4 2013/04/09 21:12:16 awachtler Exp $ */
/* Example use of the buffer functions */
#include <stdio.h>
#include "board.h"
#include "hif.h"
#include "radio.h"
#include "xmpl.h"



int main(void)
{

/* buffer is smaller than a limmerick line */
#define XMPL_FRAME_SIZE (40)
/*two byte more for the CRC */
uint8_t txbuf[sizeof(buffer_t) + XMPL_FRAME_SIZE + 2];

uint8_t frame_header[] = {0x01, 0x80, 0, 0x11,0x22,0x33,0x44};
buffer_t *pbuf;
//                           1         2         3         4
//                  1234567890123456789012345678901234567890123456789
char limmerick[] = "A wonderful bird is the pelican,\n\r"
                   "His bill will hold more than his belican,\n\r"
                   "He can take in his beak\n\r"
                   "Enough food for a week\n\r"
                   "But I'm damned if I see how the helican!\n\r\n\r";

char *plim;

    /* Prerequisite: Init radio */
    LED_INIT();
    radio_init(NULL, 0);
    sei();
    radio_set_param(RP_CHANNEL(CHANNEL));
    radio_set_state(STATE_TX);

    /* Initialize the buffer structure */
    pbuf = buffer_init(txbuf, sizeof(txbuf)-2, sizeof(frame_header));
    plim = limmerick;
    while(1)
    {
        /* fill buffer until '\n' or '\0' or EOF is reached */
        do
        {
            if (buffer_append_char(pbuf, *plim) == EOF)
            {
                break;
            }
            plim++;
        }
        while (*plim != 0 && *plim != '\n');

        /* finalize the buffer and transmit it */
        buffer_prepend_block(pbuf, frame_header, sizeof(frame_header));
        radio_set_state(STATE_TX);
        radio_send_frame(BUFFER_SIZE(pbuf)+ 2, BUFFER_PDATA(pbuf), 0);

        /* wait after this run */
        LED_TOGGLE(0);
        WAIT_MS(500);

        /* prepare next run */
        BUFFER_RESET(pbuf,sizeof(frame_header));
        frame_header[2]++;
        if (*plim == 0) plim = limmerick;
    }
}
/* XEOF */