From cea60ead2bd12f6034b6948221aa2b737e52e513 Mon Sep 17 00:00:00 2001
From: Zilog80 <rs1729@users.noreply.github.com>
Date: Sun, 9 Sep 2018 20:08:09 +0200
Subject: [PATCH] LMS6-ECC: FRAME 300 / RS-BLOCK (255+5)

---
 lms6/lms6.txt  | 25 ++++++++++++++++++++++---
 lms6/lms6ecc.c | 17 ++++++++++-------
 2 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/lms6/lms6.txt b/lms6/lms6.txt
index 34360d8..3dee373 100644
--- a/lms6/lms6.txt
+++ b/lms6/lms6.txt
@@ -2,6 +2,7 @@
 Lockheed Martin Sippican LMS6
 (403 MHz)
 
+
 FSK 4800 baud
 NRZ-S, convolutional code R=1/2
     K=8: 0x95: pA = x^7+x^4+x^2+1 = (x+1)(x^6+x^5+x^4+x+1)        = (x+1)qA
@@ -12,11 +13,29 @@ NRZ-S, convolutional code R=1/2
 bits: little endian
 bytes: big endian
 
-Reed-Solomon RS(223,32)-CCSDS
-(msg[223],par[32]): 223+32 byte vor 5-byte-Block [00 58 f3 3f b8] (ring-buffer!)
 
+4800 bit/s: rate=1/2: 300 byte/s
+
+Reed-Solomon RS(223,32)-CCSDS blocks
+block format: SYNC (5 byte) + RS-codeword (255 byte) (-> block size: 260 byte)
+SYNC: 0x0058f33fb8
+RS-codeword: RS-MSG (223 byte) + RS-PAR (32 byte)
+
+260:300 = 13:15 - every 13 sec block-position repeats,
+full-frame length 13 sec (data-frames): 13*300 byte = 15 blocks
+
+1 data-frame per sec: 223 DATA bytes ( + fill)
+DATA = 221 byte + 2 byte CRC16
+DATA: 24 54 00 00 .. (len=221+2)
 CRC16: poly 0x1021
-crc-frame: 24 54 00 00 00 .. (len=221)
+
+synchronisation:
+a) (24)54 00 00 .. (DATA-frame)
+b) (00)58 f3 3f b8 (RS-block)
+
+every 6/7 sec: DATA=RS-MSG | SYNC | ...
+
+
 
 
 sync/header:
diff --git a/lms6/lms6ecc.c b/lms6/lms6ecc.c
index 766885d..4abad53 100644
--- a/lms6/lms6ecc.c
+++ b/lms6/lms6ecc.c
@@ -4,7 +4,7 @@
    (403 MHz)
 
     gcc lms6ecc.c -lm -o lms6ecc
-    ./lms6ecc -v -b --ecc <audio.wav>
+    ./lms6ecc -v -b --ecc2 <audio.wav>
 */
 
 #include <stdio.h>
@@ -228,6 +228,12 @@ ui8_t *frame_bytes = frame+OFS; // { 0x00, 0x7A, ... }
 
 ui8_t *p_frame = frame;
 
+// RS-SYNC
+// (00)              58               f3               3f               b8              
+//  ................ 0000001011110011 1110110100100011 0110100000001011 0101110001011110
+ui8_t rs_sync[] = { 0x00, 0x58, 0xf3, 0x3f, 0xb8};
+
+
 char buf[HEADLEN];
 int bufpos = -1;
 
@@ -748,16 +754,13 @@ int get_GPSvel24() {
 #define rs_K 223
 #define rs_R (rs_N-rs_K) // 32
 ui8_t rs_cw[rs_N];
-int eccnt = 0;
-
-ui8_t rs_ecc32end[] = { 0x00, 0x58, 0xf3, 0x3f, 0xb8};
-
-ui8_t frm_bytes[FRAME_LEN+OVERLAP +8];
 
 #define ECCBUF_LEN (3*FRAME_LEN+32)
 ui8_t ecc_buf[ECCBUF_LEN];
 int bufidx = 0;
 
+ui8_t frm_bytes[FRAME_LEN+OVERLAP +8];
+
 typedef struct {
     int pos;
     ui8_t bytes[FRAME_LEN+OVERLAP+5 +8];
@@ -890,7 +893,7 @@ void proc_frame(int len) {
     pos = 0;
     for (n = 0; n < flen-rs_R-5; n++) {
         int bf = 0;
-        for (j = 0; j < 5; j++) bf += (frm_bytes[n+rs_R+j] == rs_ecc32end[j]);
+        for (j = 0; j < 5; j++) bf += (frm_bytes[n+rs_R+j] == rs_sync[j]);
         if (bf == 5) {
             if (k < kMAX) {
                 rsbf[k].epos = rs_R + n;