diff options
Diffstat (limited to 'reset-controller/fw/src/protocol.c')
| -rw-r--r-- | reset-controller/fw/src/protocol.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/reset-controller/fw/src/protocol.c b/reset-controller/fw/src/protocol.c new file mode 100644 index 0000000..6b7d8b7 --- /dev/null +++ b/reset-controller/fw/src/protocol.c @@ -0,0 +1,44 @@ + +#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); +} + |