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#include <assert.h>
#include "sr_global.h"
#include "dsss_demod.h"
#include "con_usart.h"
#include "rslib.h"
#include "crypto.h"
void handle_dsss_received(uint8_t data[static TRANSMISSION_SYMBOLS]) {
/* Console status output */
con_printf("DSSS data received: ");
for (int i=0; i<TRANSMISSION_SYMBOLS; i++) {
int x = (data[i]>>1) * (data[i]&1 ? 1 : -1);
con_printf("%3d ", x);
}
con_printf("\r\n");
/* Run reed-solomon error correction */
const int sym_bits = DSSS_GOLD_CODE_NBITS + 1; /* +1 for amplitude sign bit */
/* TODO identify erasures in DSSS demod layer */
(void) rslib_decode(sym_bits, TRANSMISSION_SYMBOLS, (char *)data);
/* TODO error detection & handling */
/* Re-bit-pack data buffer to be bit-continuous:
* [ . . a b c d e f ] [ . . g h i j k l ] [ . . m n o p q r ] ...
* ==> [ a b c d e f g h ] [ i j k l m n o p ] [ q r ... ] ...
*/
static_assert((TRANSMISSION_SYMBOLS - NPAR) * (DSSS_GOLD_CODE_NBITS + 1) == OOB_TRIGGER_LEN * 8);
for (uint8_t i=0, j=0; i < TRANSMISSION_SYMBOLS - NPAR; i++, j += sym_bits) {
uint32_t sym = data[i]; /* [ ... | . . X X X X X X ] for 5-bit dsss */
data[i] = 0; /* clear for output */
sym <<= 8-sym_bits; /* left-align: [ ... | X X X X X X . . ] */
sym <<= 8; /* shift to second byte: [ ... | X X X X X X . . | . . . . . . . . ]*/
sym >>= (j%8); /* shift to bit write offset: [ ... | . . . . X X X X | X X . . . . . . ] for offset 4 */
data[j/8] |= sym >> 8; /* write upper byte */
data[j/8 + 1] |= sym & 0xff; /* write lower byte */
}
/* hand off to crypto.c */
oob_message_received(data);
}
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