first pass simultaneous two raw date mode tx/rx

Author: drowe67

README_freedv.md

@@ -34,6 +34,8 @@ The current demo programs are as follows:
 | [freedv_700d_rx.py](demo/freedv_700d_rx.py) | Receive a voice signal using the FreeDV API in Python |
 | [freedv_datac1_tx.c](demo/freedv_datac1_tx.c) | Transmit raw data frames using the FreeDV API |
 | [freedv_datac1_rx.c](demo/freedv_datac1_rx.c) | Receive raw data frames using the FreeDV API |
+| [freedv_datac0c1_tx.c](demo/freedv_datac0c1_tx.c) | Transmit two types of raw data frames using the FreeDV API |
+| [freedv_datac0c1_rx.c](demo/freedv_datac0c1_rx.c) | Receive two types of raw data frames using the FreeDV API |
 
 So also [freedv_api.h](src/freedv_api.h) and [freedv_api.c](src/freedv_api.c) for the full list of API functions.  Only a small set of these functions are needed for basic FreeDV use, please see the demo programs for minimal examples.
 

demo/CMakeLists.txt

@@ -11,5 +11,7 @@ add_executable(freedv_datac1_tx freedv_datac1_tx.c)
 target_link_libraries(freedv_datac1_tx codec2)
 add_executable(freedv_datac1_rx freedv_datac1_rx.c)
 target_link_libraries(freedv_datac1_rx codec2)
+add_executable(freedv_datac0c1_tx freedv_datac0c1_tx.c)
+target_link_libraries(freedv_datac0c1_tx codec2)
 add_executable(freedv_datac0c1_rx freedv_datac0c1_rx.c)
 target_link_libraries(freedv_datac0c1_rx codec2)

demo/freedv_datac0c1_rx.c

@@ -4,11 +4,14 @@
   AUTHOR......: David Rowe
   DATE CREATED: Dec 2021
 
-  Demonstrates receiving frames of raw data bytes using the FreeDV API.  Two
-  parallel receivers are running, so we can receive either DATAC0 or DATAC1
-  frames.
-
-  See freedv_datac0c1_tx.c for instructions.
+  Demonstrates receiving frames of raw data bytes using the FreeDV
+  API.  Two parallel receivers are running, so we can receive either
+  DATAC0 or DATAC1 frames.  Demonstrates a common use case for HF data
+  - the ability to receive signalling as well as payload data frames.
+
+  usage: 
+  cd codec2/build_linux
+  ./demo/freedv_datacc01_tx | ./demo/freedv_datac0c1_rx
   
 \*---------------------------------------------------------------------------*/
 
@@ -69,18 +72,19 @@ int main(int argc, char *argv[]) {
     int c1_frames = 0;
 
     short buf[NBUF];
-    
+
+    // read a fixed buffer from stdin, use that to fill c0 and c1 demod_in buffers
     while(fread(buf, sizeof(short), NBUF, stdin) == NBUF) {
 
+        if (run_receiver(freedv_c0, buf, demod_in_c0, &n_c0, bytes_out_c0)) {
+            fprintf(stderr, "DATAC0 frame received!\n");
+            c0_frames++;
+        }
         if (run_receiver(freedv_c1, buf, demod_in_c1, &n_c1, bytes_out_c1)) {
             fprintf(stderr, "DATAC1 frame received!\n");
             c1_frames++;
         }
 
-        if (run_receiver(freedv_c0, buf, demod_in_c0, &n_c0, bytes_out_c0)) {
-            fprintf(stderr, "DATAC0 frame received!\n");
-            c1_frames++;
-        }
     }
 
     fprintf(stderr, "DATAC0 Frames: %d\n", c0_frames);

demo/freedv_datac0c1_tx.c

@@ -0,0 +1,93 @@
+/*---------------------------------------------------------------------------*\
+
+  FILE........: freedv_datac0c1_tx.c
+  AUTHOR......: David Rowe
+  DATE CREATED: Dec 2021
+
+  Transmitting alternate frames of two different raw data modes.  See
+  freedv_datac0c1_rx.c
+  
+\*---------------------------------------------------------------------------*/
+
+/*
+  Copyright (C) 2021 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 <stdio.h>
+#include <stdint.h>
+
+#include "freedv_api.h"
+#include "ofdm_internal.h"
+
+void send_burst(struct freedv *freedv);
+
+int main(void) {
+    struct freedv *freedv_c0, *freedv_c1;
+
+    freedv_c0 = freedv_open(FREEDV_MODE_DATAC0); assert(freedv_c0 != NULL);
+    freedv_c1 = freedv_open(FREEDV_MODE_DATAC1); assert(freedv_c1 != NULL);
+
+    for(int b=0; b<10; b++) {
+        send_burst(freedv_c0);
+        send_burst(freedv_c1);
+    }
+
+    freedv_close(freedv_c0);
+    freedv_close(freedv_c1);
+
+    return 0;
+}
+
+
+void send_burst(struct freedv *freedv) {
+    size_t bits_per_frame = freedv_get_bits_per_modem_frame(freedv);
+    size_t bytes_per_modem_frame = bits_per_frame/8;
+    size_t payload_bytes_per_modem_frame = bytes_per_modem_frame - 2; /* 16 bits used for the CRC */
+    size_t n_mod_out = freedv_get_n_tx_modem_samples(freedv);
+    uint8_t bytes_in[bytes_per_modem_frame];
+    short mod_out_short[n_mod_out];
+
+    /* generate a test frame */
+    uint8_t testframe_bits[bits_per_frame];
+    ofdm_generate_payload_data_bits(testframe_bits, bits_per_frame);
+    freedv_pack(bytes_in, testframe_bits, bits_per_frame);
+    
+    /* send preamble */
+    int n_preamble = freedv_rawdatapreambletx(freedv, mod_out_short);
+    fwrite(mod_out_short, sizeof(short), n_preamble, stdout);
+        
+    /* The raw data modes require a CRC in the last two bytes */
+    uint16_t crc16 = freedv_gen_crc16(bytes_in, payload_bytes_per_modem_frame);
+    bytes_in[bytes_per_modem_frame-2] = crc16 >> 8;
+    bytes_in[bytes_per_modem_frame-1] = crc16 & 0xff;
+
+    /* modulate and send a data frame */
+    freedv_rawdatatx(freedv, mod_out_short, bytes_in);
+    fwrite(mod_out_short, sizeof(short), n_mod_out, stdout);
+                    
+    /* send postamble */
+    int n_postamble = freedv_rawdatapostambletx(freedv, mod_out_short);
+    fwrite(mod_out_short, sizeof(short), n_postamble, stdout);
+
+    /* create some silence between bursts */
+    int inter_burst_delay_ms = 200;
+    int samples_delay = FREEDV_FS_8000*inter_burst_delay_ms/1000;
+    short sil_short[samples_delay];
+    for(int i=0; i<samples_delay; i++) sil_short[i] = 0;
+    fwrite(sil_short, sizeof(short), samples_delay, stdout);
+}