Extra parameter for aprs_pico_send_sine_wave()

CMakeLists.txt

@@ -6,7 +6,6 @@ include(cmake/pico_extras_import.cmake) # File copied from $PICO_SDK_PATH/../pic
 project(raspi-pico-aprs-tnc VERSION 0.1)
 
 set(CMAKE_C_STANDARD 11)
-set(CMAKE_CXX_STANDARD 17)
 
 pico_sdk_init()
 

README.md

@@ -48,7 +48,7 @@ cmake -S . -B build
 cmake --build build
 ```
 
-`build/lib/libaprs_pico.a` and `build/aprs_pico_example.uf2|.elf|.xxx` will be generated.
+`build/lib/libaprs_pico.a` and `build/aprs_pico_example[.uf2|.elf|.bin]` will be generated.
 
 ## Run the example application
 
@@ -59,12 +59,38 @@ Flash 'aprs_pico_example[.uf2|.elf|.bin]' to the Pico board as usual
 
 The analog AFSK audio signal will be available at the filter's line-out. You can probe it by a scope, listen to it by using an audio amp, or connect it to any RF transceiver to send it on the air (ham radio license required).
 
-## TODO (Sept. 2021)
+## Test the example application using *Dire Wolf* (on LINUX)
+
+We can use the famous [Dire Wolf](https://github.com/wb2osz/direwolf) CLI software to decode the APRS data after sampling our APRS audio signal by means of a soundcard.
+
+1. Connect the line-out of our circuit above to the microphone input of your soundcard of your (ALSA-supported) LINUX system.
+2. Check if you can hear the typical APRS 'modem-sound' on your audio output device by monitoring the input signal:
+
+```
+arecord -f cd -c 1 -t raw - | aplay -f cd -c 1 -t raw
+```
+
+3. Install [Dire Wolf](https://github.com/wb2osz/direwolf) on your system. Probably, you just have to run:
+
+```
+sudo apt install direwolf
+```
+
+4. Let's sample the APRS audio signal fed to the soundcard and forward the audio stream to *Dire Wolf*:
+
+```
+arecord -f cd -c 1 -t raw - | direwolf
+```
+
+5. Enjoy the decoded APRS message:
+
+![Decoded APRS message by Dire Wolf](https://github.com/eleccoder/raspi-pico-aprs-tnc/blob/main/doc/img/direwolf_decoding.png)
+
+## TODO (Dec. 2022)
 
-- [x] Thorough evaluation, in general
 - [x] Send the APRS message on the console (USB or UART) rather than hard-coding
-- [x] Show how to physically connect to a Baofeng HT
 - [x] PTT control for RF transceivers
+- [x] Show how to physically connect to a Baofeng HT
 
 ## Ingredients / Acknowledgements
 

include/aprs_pico.h

@@ -65,8 +65,9 @@ bool aprs_pico_sendAPRS(audio_buffer_pool_t* audio_buffer_pool,
  *
  * \param[in, out] audio_buffer_pool  The pool of audio buffers to be used for rendering the sine audio signal
  * \param[in]      freq_in_hz         The frequency of the sine wave to be generated (in Hz)
+ * \param[in]      sample_freq_in_hz  The sampling frequency of the sine wave to be generated (in Hz)
  * \param[in]      volume             The volume level of the generated signal (0 ... 256)
  */
-void aprs_pico_send_sine_wave(audio_buffer_pool_t* audio_buffer_pool, unsigned int freq_in_hz, uint16_t volume);
+void aprs_pico_send_sine_wave(audio_buffer_pool_t* audio_buffer_pool, unsigned int freq_in_hz, unsigned int sample_freq_in_hz, uint16_t volume);
 
 #endif // APRS_PICO_H

src/aprs_pico.c

@@ -116,19 +116,23 @@ static void aprs_pico_renderAudioSamples(audio_buffer_pool_t* audio_buffer_pool,
   assert(audio_buffer_pool != NULL);
   assert(pcm_data          != NULL);
 
-  unsigned int idx_src       = 0u;
-  bool         is_keep_going = true;
+  unsigned int idx_src                  = 0u;
+  bool         is_all_samples_processed = num_samples == 0u;
 
-  // Write the PCM sample data into the audio buffer(s) while applying the 'volume' value
-  while (is_keep_going)
+  // Write the PCM sample data into the next audio buffer while applying the 'volume' value
+  while (!is_all_samples_processed)
     {
       audio_buffer_t* audio_buffer          = take_audio_buffer(audio_buffer_pool, true);
       int16_t*        audio_buffer_pcm_data = (int16_t*)audio_buffer->buffer->bytes;
 
-      for (unsigned int idx_dst = 0u; idx_dst < audio_buffer->max_sample_count; idx_dst++)
+      unsigned int idx_dst = 0u;
+
+      while (!is_all_samples_processed && (idx_dst < audio_buffer->max_sample_count))
         {
           audio_buffer_pcm_data[idx_dst] = ((int32_t)volume * (int32_t)pcm_data[idx_src]) >> 8u;
+
           idx_src++;
+          idx_dst++;
 
           if (idx_src == num_samples)
             {
@@ -138,13 +142,15 @@ static void aprs_pico_renderAudioSamples(audio_buffer_pool_t* audio_buffer_pool,
                 }
               else
                 {
-                  is_keep_going = false;
-                  break;
+                  is_all_samples_processed = true;
                 }
             }
         }
 
-      audio_buffer->sample_count = audio_buffer->max_sample_count;
+      assert(idx_src <= num_samples);
+      assert(idx_dst <= audio_buffer->max_sample_count);
+
+      audio_buffer->sample_count = idx_dst;
       give_audio_buffer(audio_buffer_pool, audio_buffer);
     }
 }
@@ -177,20 +183,17 @@ audio_buffer_pool_t* aprs_pico_init()
 
 
 // See the header file for documentation
-void aprs_pico_send_sine_wave(audio_buffer_pool_t* audio_buffer_pool, unsigned int freq_in_hz, uint16_t volume)
+void aprs_pico_send_sine_wave(audio_buffer_pool_t* audio_buffer_pool, unsigned int freq_in_hz, unsigned int sample_freq_in_hz, uint16_t volume)
 {
   assert(audio_buffer_pool != NULL);
 
-  // WARNING: ATTOW, the pico audio PWM lib worked only @ 22050 Hz sampling frequency and 48 MHz system clock
-  //          This is documented here: https://github.com/raspberrypi/pico-extras
-  const unsigned int SAMPLE_FREQ_IN_HZ      = APRS_PICO__PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ;
-  const unsigned int num_samples_per_period = SAMPLE_FREQ_IN_HZ / freq_in_hz;
-
   typedef int16_t wave_table_value_t;
   const wave_table_value_t WAVE_TABLE_VALUE_MAX = INT16_MAX;
 
 
-  aprs_pico_initClock(SAMPLE_FREQ_IN_HZ);
+  aprs_pico_initClock(sample_freq_in_hz);
+
+  const unsigned int num_samples_per_period = sample_freq_in_hz / freq_in_hz;
 
   wave_table_value_t* sine_period_wave_table = malloc(num_samples_per_period * sizeof(wave_table_value_t));
 

src/aprs_pico_example.c

@@ -31,26 +31,31 @@ int main()
 
 #if (SINE_WAVE_TEST == 1)
 
-  const unsigned int FREQ_IN_HZ = 1000u;
-  const uint16_t     VOLUME     = 128u;
+  const unsigned int FREQ_IN_HZ        = 1000u;
+  const unsigned int SAMPLE_FREQ_IN_HZ = 48000u;
+  const uint16_t     VOLUME            = 128u;
 
-  aprs_pico_send_sine_wave(audio_buffer_pool, FREQ_IN_HZ, VOLUME);
+  aprs_pico_send_sine_wave(audio_buffer_pool, FREQ_IN_HZ, SAMPLE_FREQ_IN_HZ, VOLUME);
 
 #else // !SINE_WAVE_TEST
 
+  double alt_in_m = 0.0f;
+
   while (true) // Loop forever
     {
       // Send an APRS test message
       aprs_pico_sendAPRS(audio_buffer_pool,
-                         "SRC",          // Source call sign
-                         "DST",          // Destination call sign
-                         "PATH1",        // APRS path #1
-                         "PATH2",        // APRS path #2
-                         "Test message", // APRS message
-                         10.0,           // Latitude  (in deg)
-                         20.0,           // Longitude (in deg)
-                         100.0,          // Altitude  (in m)
-                         128u);          // Volume    (0 ... 256)
+                         "DL3TG",  // Source call sign
+                         "DL3TG",  // Destination call sign
+                         "PATH1",  // APRS path #1
+                         "PATH2",  // APRS path #2
+                         "APRS by RPi-Pico - https://github.com/eleccoder/raspi-pico-aprs-tnc", // APRS message
+                         10.0,     // Latitude  (in deg)
+                         20.0,     // Longitude (in deg)
+                         alt_in_m, // Altitude  (in m)
+                         128u);    // Volume    (0 ... 256)
+
+      alt_in_m = (alt_in_m < 1000.0) ? alt_in_m + 100.0 : 0.0;
     }
 
 #endif // SINE_WAVE_TEST, !SINE_WAVE_TEST