From 268446a633c590c6edc812732533e3778482cd4c Mon Sep 17 00:00:00 2001
From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Sun, 6 Mar 2016 02:21:00 +0000
Subject: [PATCH] working with test files

git-svn-id: https://svn.code.sf.net/p/freetel/code@2714 01035d8c-6547-0410-b346-abe4f91aad63
---
 codec2-dev/src/drs232.c | 197 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 197 insertions(+)
 create mode 100644 codec2-dev/src/drs232.c

diff --git a/codec2-dev/src/drs232.c b/codec2-dev/src/drs232.c
new file mode 100644
index 00000000..f0a08ef1
--- /dev/null
+++ b/codec2-dev/src/drs232.c
@@ -0,0 +1,197 @@
+/*---------------------------------------------------------------------------*\
+
+  FILE........: drs232.c
+  AUTHOR......: David Rowe
+  DATE CREATED: March 2016
+
+  Looks for a unique word in series of bits.  When found, deframes a RS232
+  encoded frame of bytes.  Used for high biit rate Horus SSTV reception.
+
+  Frame format:
+
+    16 bytes 0x55 - 0xabcd UW - 256 bytes of payload - 2 bytes CRC
+
+  Each byte is encoded as a 10 bit RS232 serial word: 
+  
+    0 LSB .... MSB 1
+
+  Building:
+   
+    $ gcc drs232.c -o drs232.c -Wall
+
+\*---------------------------------------------------------------------------*/
+
+
+/*
+  Copyright (C) 2016 David Rowe
+
+  All rights reserved.
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License version 2.1, as
+  published by the Free Software Foundation.  This program is
+  distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+  License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <assert.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+/* states -----------------------------------------------*/
+
+#define LOOK_FOR_UW    0
+#define COLLECT_PACKET 1
+
+/* packet parameters */
+
+#define UW_BYTES               2
+#define UW_BITS                20
+#define BYTES_PER_PACKET       256
+#define CRC_BYTES              2
+#define BITS_PER_BYTE          10
+#define UNPACKED_PACKET_BYTES  ((UW_BYTES+BYTES_PER_PACKET+CRC_BYTES)*BITS_PER_BYTE)
+
+/* UW pattern we look for, inclduing start/stop bits */
+
+uint8_t uw[] = {
+    /* 0xb                0xa */
+    0, 1, 1, 0, 1, 0, 1, 0, 1, 1,
+    /* 0xd                0xc */
+    0, 1, 0, 1, 1, 0, 0, 1, 1, 1,
+};
+
+ // from http://stackoverflow.com/questions/10564491/function-to-calculate-a-crc16-checksum
+
+unsigned short gen_crc16(unsigned char* data_p, int length){
+    unsigned char x;
+    unsigned short crc = 0xFFFF;
+
+    while (length--){
+        x = crc >> 8 ^ *data_p++;
+        x ^= x>>4;
+        crc = (crc << 8) ^ ((unsigned short)(x << 12)) ^ ((unsigned short)(x <<5)) ^ ((unsigned short)x);
+    }
+    
+    return crc;
+}
+
+
+int main(int argc, char *argv[]) {
+    FILE       *fin, *fout;
+    int         state, next_state, i, j, k, ind, score, bits_read;
+    char        bit;
+    uint8_t     unpacked_packet[UNPACKED_PACKET_BYTES];
+    uint8_t     packet[BYTES_PER_PACKET+CRC_BYTES];
+    uint8_t     abyte;
+    uint16_t    tx_checksum, rx_checksum;
+
+    if (argc < 3) {
+	printf("usage: drs232 InputOneBitPerChar OutputPackets\n");
+	exit(1);
+    }
+
+    if (strcmp(argv[1], "-")  == 0) fin = stdin;
+    else if ( (fin = fopen(argv[1],"rb")) == NULL ) {
+	fprintf(stderr, "Error opening input speech file: %s: %s.\n",
+         argv[2], strerror(errno));
+	exit(1);
+    }
+
+    if (strcmp(argv[2], "-") == 0) fout = stdout;
+    else if ( (fout = fopen(argv[2],"wb")) == NULL ) {
+	fprintf(stderr, "Error opening output speech file: %s: %s.\n",
+         argv[3], strerror(errno));
+	exit(1);
+    }
+
+    state = LOOK_FOR_UW;
+    for(i=0; i<UNPACKED_PACKET_BYTES; i++)
+        unpacked_packet[i] = 0;
+    bits_read = 0;
+
+    while(fread(&bit, sizeof(char), 1, fin) == 1) {
+        bits_read++;
+        if (state == LOOK_FOR_UW) {
+
+            /* put latest input bit into sliding buffer */
+            
+            for(i=0; i<UW_BITS-1; i++) {
+                unpacked_packet[i] = unpacked_packet[i+1];
+            }
+            unpacked_packet[i] = bit;
+
+            /* lets see if it matches the UW */
+
+            score = 0;
+            for(i=0; i<UW_BITS; i++) {
+                score += (unpacked_packet[i] == uw[i]);
+                /* if (i == BITS_PER_BYTE)
+                    printf(" ");
+                    printf("%1d", unpacked_packet[i]); */
+            }
+            //printf("\n");
+            
+            //fprintf(stderr,"UW score: %d\n", score);
+            if (score == UW_BITS) {
+                fprintf(stderr,"UW found!\n");
+                ind = UW_BITS;
+                next_state = COLLECT_PACKET;
+            }             
+        }
+
+        if (state == COLLECT_PACKET) {
+            unpacked_packet[ind++] = bit;
+ 
+           if (ind == UNPACKED_PACKET_BYTES) {
+
+               /* OK we have enough bits, remove RS232 sync bits and pack */
+
+               for(i=UW_BITS,k=0; i<UNPACKED_PACKET_BYTES; i+=BITS_PER_BYTE,k++) {
+                   //for(j=0; j<BITS_PER_BYTE; j++)
+                   //    printf("%1d", unpacked_packet[i+j]);
+                   //printf("\n");
+                   abyte = 0;
+                   for(j=0; j<8; j++) {
+                       abyte |= unpacked_packet[i+j+1] << j;
+                   }
+                   packet[k] = abyte;
+                   //printf("k:%d 0x%02x\n", k, packet[k]);
+                   //if (k == 4)
+                   //  exit(0);
+               }
+
+               /* output if CRC check is OK */
+
+               rx_checksum = gen_crc16(packet, BYTES_PER_PACKET);
+               tx_checksum = packet[BYTES_PER_PACKET] + (packet[BYTES_PER_PACKET+1] << 8);
+
+               fprintf(stderr, "k=%d bytes after UW  tx_checksum: 0x%02x rx_checksum: 0x%02x\n", k, tx_checksum, rx_checksum);
+
+               if (rx_checksum == tx_checksum) {
+                   fwrite(packet, sizeof(char), BYTES_PER_PACKET, fout);
+               }
+
+               next_state = LOOK_FOR_UW;
+            }
+
+        }
+        //if (bits_read == (16*10 + UNPACKED_PACKET_BYTES))
+        //    exit(0);
+
+        state = next_state;      
+    }
+
+    fclose(fin);
+    fclose(fout);
+
+    return 0;
+}
-- 
2.25.1