Commit 34ae5f14 authored by Manolis Surligas's avatar Manolis Surligas

Fix CRC16 calculation and transmission

The CC1120 uses the non-reversed version of the CRC16-CCIIT. Also the
CRC16 is transmitted in network byte order
parent 0c354da1
......@@ -76,8 +76,42 @@ namespace gr
0xE606, 0xD49D, 0xC514, 0xB1AB, 0xA022, 0x92B9, 0x8330, 0x7BC7,
0x6A4E, 0x58D5, 0x495C, 0x3DE3, 0x2C6A, 0x1EF1, 0x0F78 };
static const uint16_t crc16_ccitt_table[256] =
{ 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7, 0x8108,
0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF, 0x1231,
0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6, 0x9339,
0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE, 0x2462,
0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485, 0xA56A,
0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D, 0x3653,
0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4, 0xB75B,
0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC, 0x48C4,
0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823, 0xC9CC,
0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B, 0x5AF5,
0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12, 0xDBFD,
0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A, 0x6CA6,
0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41, 0xEDAE,
0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49, 0x7E97,
0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70, 0xFF9F,
0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78, 0x9188,
0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F, 0x1080,
0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067, 0x83B9,
0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E, 0x02B1,
0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256, 0xB5EA,
0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D, 0x34E2,
0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xA7DB,
0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C, 0x26D3,
0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634, 0xD94C,
0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB, 0x5844,
0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3, 0xCB7D,
0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A, 0x4A75,
0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92, 0xFD2E,
0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9, 0x7C26,
0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1, 0xEF1F,
0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8, 0x6E17,
0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0 };
static inline uint16_t
update_crc16_ccitt(uint16_t crc, const uint8_t *data, size_t len)
update_crc16_ccitt_reversed(uint16_t crc, const uint8_t *data, size_t len)
register size_t i;
for (i = 0; i < len; i++) {
......@@ -86,10 +120,25 @@ namespace gr
return crc;
static inline uint16_t
crc16_ccitt_reversed(const uint8_t *data, size_t len)
return update_crc16_ccitt_reversed(0xFFFF, data, len) ^ 0xFFFF;
static uint16_t
update_crc16_ccitt (uint16_t crc, const uint8_t *buf, size_t len)
while (len-- != 0) {
crc = crc16_ccitt_table[((crc >> 8) ^ *buf++) & 0xff] ^ (crc << 8);
return crc;
static inline uint16_t
crc16_ccitt(const uint8_t *data, size_t len)
return update_crc16_ccitt(0xFFFF, data, len) ^ 0xFFFF;
return update_crc16_ccitt(0x0000, data, len);
......@@ -26,6 +26,7 @@
#include "upsat_fsk_frame_acquisition_impl.h"
#include <satnogs/log.h>
#include <satnogs/utils.h>
#include <arpa/inet.h>
namespace gr
......@@ -269,6 +270,8 @@ namespace gr
/* Retrieve and check the CRC */
memcpy(&crc_received, d_pdu + d_frame_len - sizeof(uint16_t),
/* The CRC is transmitted in network byte order */
crc_received = ntohs(crc_received);
crc_calc = crc16_ccitt(d_pdu, d_frame_len - sizeof(uint16_t));
if(crc_calc == crc_received) {
message_port_pub (
......@@ -277,7 +280,8 @@ namespace gr
d_frame_len - 1 - sizeof(uint16_t)));
LOG_WARN("Frame with wrong CRC");
LOG_WARN("Frame with wrong CRC got 0x%x calc 0x%x",
crc_received, crc_calc);
reset_state ();
......@@ -26,6 +26,7 @@
#include "upsat_fsk_frame_encoder_impl.h"
#include <satnogs/log.h>
#include <satnogs/utils.h>
#include <arpa/inet.h>
namespace gr
......@@ -173,6 +174,8 @@ namespace gr
if(d_append_crc) {
crc = crc16_ccitt(d_pdu + d_preamble_len + d_sync_word_len,
d_pdu_len + 1);
/* CRC must be transmitted MSB first */
crc = htons(crc);
memcpy(d_pdu + d_preamble_len + d_sync_word_len + 1 + d_pdu_len,
&crc, sizeof(uint16_t));
d_pdu_len += sizeof(uint16_t);
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