/*! \brief This function will upload a frame from the radio transceiver's frame
* buffer.
*
* If the frame currently available in the radio transceiver's frame buffer
* is out of the defined bounds. Then the frame length, lqi value and crc
* be set to zero. This is done to indicate an error.
*
* \param rx_frame Pointer to the data structure where the frame is stored.
*
* \ingroup hal_avr_api
*/
void hal_frame_read( hal_rx_frame_t *rx_frame )
{
uint8_t frame_length;
AVR_ENTER_CRITICAL_REGION( );
HAL_SS_LOW( );
//Send frame read command.
frame_length=hal_RF_SPI_Send_Data(HAL_TRX_CMD_FR); //
frame_length=hal_RF_SPI_Send_Data(frame_length);
//delay_ms(1);
/*Check for correct frame length.*/
if ((frame_length >= HAL_MIN_FRAME_LENGTH) && (frame_length <= HAL_MAX_FRAME_LENGTH)) {
uint16_t crc = 0;
uint8_t *rx_data = (rx_frame->data);
uint8_t tempData;
rx_frame->length = frame_length; //Store frame length.
/*Upload frame buffer to data pointer. Calculate CRC.*/
do{
tempData = hal_RF_SPI_Send_Data(frame_length);
*rx_data++ = tempData;
crc = crc_ccitt_update( crc, tempData );
} while (--frame_length > 0);
/*Read LQI value for this frame.*/
rx_frame->lqi = hal_RF_SPI_Send_Data( tempData);
HAL_SS_HIGH( );
/*Check calculated crc, and set crc field in hal_rx_frame_t accordingly.*/
if (crc == HAL_CALCULATED_CRC_OK) {
rx_frame->crc = true;
} else { rx_frame->crc = false; }
} else {
HAL_SS_HIGH( );
rx_frame->length = 0;
rx_frame->lqi = 0;
rx_frame->crc = false;
}
AVR_LEAVE_CRITICAL_REGION( );
}
ssize_t frame_send(FILE *out, void *data, size_t nbytes)
{
char *d;
char *end;
uint16_t crc = FRAME_CRC_INIT;
fputc(FRAME_START, out);
for(d = data, end = d + nbytes; d < end; d++) {
char c = *d;
crc = crc_ccitt_update(crc, c);
SEND_BYTE(out, c);
}
crc = htons(crc);
SEND_BYTE(out, crc >> 8);
SEND_BYTE(out, crc & 0xff);
fputc(FRAME_START, out);
fflush(out);
return nbytes;
}
ssize_t frame_recv(FILE *in, void *vbuf, size_t nbytes)
{
uint16_t crc = FRAME_CRC_INIT;
size_t i;
char *buf = vbuf;
bool recv_started = false;
bool is_escaped = false;
for(i = 0;;) {
int data = fgetc(in);
if (data == EOF) {
return EOF;
}
if (data < 0) {
return data;
}
if (ferror(in)) {
return -255;
}
if (data == FRAME_START) {
if (recv_started) {
if (i != 0) {
/* success */
if (crc == 0) {
ungetc(data, in);
return i - 2;
} else {
fprintf(stderr, "crc = %d\n", crc);
i = 0;
crc = FRAME_CRC_INIT;
continue;
}
}
} else {
recv_started = true;
}
continue;
}
if (!recv_started)
continue;
if (data == FRAME_RESET) {
/* restart recv */
i = 0;
continue;
}
if (data == FRAME_ESC) {
is_escaped = true;
continue;
}
if (is_escaped) {
is_escaped = false;
data ^= FRAME_ESC_MASK;
}
crc = crc_ccitt_update(crc, (uint8_t)(data & 0xff));
if (i < nbytes) {
buf[i] = data;
i++;
} else {
return -ENOSPC;
}
}
return i;
}
