Copyright notice updated

CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.15)
 
-include(cmake/pico_sdk_import.cmake)    # File copied from $PICO_SDK_PATH/pico-sdk/external
-include(cmake/pico_extras_import.cmake) # File copied from $PICO_SDK_PATH/pico-extras/external
+include(cmake/pico_sdk_import.cmake)    # File copied from $PICO_SDK_PATH/external
+include(cmake/pico_extras_import.cmake) # File copied from $PICO_SDK_PATH/../pico-extras/external
 
 project(raspi-pico-aprs-tnc VERSION 0.1)
 
@@ -11,7 +11,7 @@ set(CMAKE_CXX_STANDARD 17)
 pico_sdk_init()
 
 
-# (1) Setup of eleccoder's version of Philip Heron's 'ax25beacon' project
+# Setup of eleccoder's version of Philip Heron's 'ax25beacon' project
 
 include(FetchContent)
 FetchContent_Declare(ax25_aprs_lib
@@ -24,7 +24,7 @@ FetchContent_MakeAvailable(ax25_aprs_lib)
 add_library(ax25_aprs_lib::ax25beacon ALIAS ax25beacon)
 
 
-# (2) Configure the library build
+# ##### Configure the build of the 'aprs_pico' library #####
 
 set(TARGET_LIB_NAME aprs_pico)
 
@@ -43,7 +43,6 @@ target_include_directories(${TARGET_LIB_NAME} PUBLIC
 # Enable on demand
 #target_compile_options(${TARGET_LIB_NAME} PRIVATE "-Wundef;-Wall")
 
-# This properly resolves the include dirs of the dependent libraries
 target_link_libraries(${TARGET_LIB_NAME}
     ax25_aprs_lib::ax25beacon
     pico_audio_pwm        
@@ -51,7 +50,7 @@ target_link_libraries(${TARGET_LIB_NAME}
 )
 
 
-# (3) Configure the example application build
+# ##### Configure the build of the example application #####
 
 set(TARGET_EXAMPLE_EXE_NAME aprs_pico_example)
 
@@ -63,11 +62,11 @@ target_include_directories(${TARGET_EXAMPLE_EXE_NAME} PRIVATE
   include
 )
 
-# Set the console interface
+# Configure the console interface
 pico_enable_stdio_usb(${TARGET_EXAMPLE_EXE_NAME} 1) # USB
 #pico_enable_stdio_uart(${TARGET_EXAMPLE_EXE_NAME} 1) # UART
 
-# create map/bin/hex file etc.
+# Create map/bin/hex file etc.
 pico_add_extra_outputs(${TARGET_EXAMPLE_EXE_NAME})
 
 target_link_libraries(${TARGET_EXAMPLE_EXE_NAME}

README.md

@@ -54,7 +54,7 @@ cmake --build build
 
 ```
 cd build
-(flash 'aprs_pico_example.uf2' or 'aprs_pico_example.elf' to the Pico board as usual)
+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).

cmake/pico_extras_import.cmake

@@ -26,14 +26,14 @@ if (NOT PICO_EXTRAS_PATH)
             get_filename_component(FETCHCONTENT_BASE_DIR "${PICO_EXTRAS_FETCH_FROM_GIT_PATH}" REALPATH BASE_DIR "${CMAKE_SOURCE_DIR}")
         endif ()
         FetchContent_Declare(
-                PICO_EXTRAS
+                pico_extras
                 GIT_REPOSITORY https://github.com/raspberrypi/pico-extras
                 GIT_TAG master
         )
-        if (NOT PICO_EXTRAS)
-            message("Downloading PICO EXTRAS")
-            FetchContent_Populate(PICO_EXTRAS)
-            set(PICO_EXTRAS_PATH ${PICO_EXTRAS_SOURCE_DIR})
+        if (NOT pico_extras)
+            message("Downloading Raspberry Pi Pico Extras")
+            FetchContent_Populate(pico_extras)
+            set(PICO_EXTRAS_PATH ${pico_extras_SOURCE_DIR})
         endif ()
         set(FETCHCONTENT_BASE_DIR ${FETCHCONTENT_BASE_DIR_SAVE})
     else ()
@@ -59,4 +59,4 @@ endif ()
 
 set(PICO_EXTRAS_PATH ${PICO_EXTRAS_PATH} CACHE PATH "Path to the PICO EXTRAS" FORCE)
 
-add_subdirectory(${PICO_EXTRAS_PATH} pico_extras)
+add_subdirectory(${PICO_EXTRAS_PATH} pico_extras)

cmake/pico_sdk_import.cmake

@@ -29,11 +29,22 @@ if (NOT PICO_SDK_PATH)
         if (PICO_SDK_FETCH_FROM_GIT_PATH)
             get_filename_component(FETCHCONTENT_BASE_DIR "${PICO_SDK_FETCH_FROM_GIT_PATH}" REALPATH BASE_DIR "${CMAKE_SOURCE_DIR}")
         endif ()
-        FetchContent_Declare(
-                pico_sdk
-                GIT_REPOSITORY https://github.com/raspberrypi/pico-sdk
-                GIT_TAG master
-        )
+        # GIT_SUBMODULES_RECURSE was added in 3.17
+        if (${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.17.0")
+            FetchContent_Declare(
+                    pico_sdk
+                    GIT_REPOSITORY https://github.com/raspberrypi/pico-sdk
+                    GIT_TAG master
+                    GIT_SUBMODULES_RECURSE FALSE
+            )
+        else ()
+            FetchContent_Declare(
+                    pico_sdk
+                    GIT_REPOSITORY https://github.com/raspberrypi/pico-sdk
+                    GIT_TAG master
+            )
+        endif ()
+
         if (NOT pico_sdk)
             message("Downloading Raspberry Pi Pico SDK")
             FetchContent_Populate(pico_sdk)

include/aprs_pico.h

@@ -1,6 +1,6 @@
 /*
 * Project 'raspi-pico-aprs-tnc'
-* Copyright (C) 2021 Thomas Glau, DL3TG
+* Copyright (C) 2021-2023 Thomas Glau, DL3TG
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
@@ -61,11 +61,12 @@ bool aprs_pico_sendAPRS(audio_buffer_pool_t* audio_buffer_pool,
                         uint16_t             volume);
 
 
-/** \brief Generates a 1 KHz sine wave PWM-signal at GPIO-pin 'GP0'
+/** \brief Generates a sine wave PWM-signal at GPIO-pin 'GP0'
  *
  * \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]      volume             The volume level of the generated signal (0 ... 256)
  */
-void aprs_pico_send1kHz(audio_buffer_pool_t* audio_buffer_pool, uint16_t volume);
+void aprs_pico_send_sine_wave(audio_buffer_pool_t* audio_buffer_pool, unsigned int freq_in_hz, uint16_t volume);
 
 #endif // APRS_PICO_H

src/aprs_pico.c

@@ -1,6 +1,6 @@
 /*
 * Project 'raspi-pico-aprs-tnc'
-* Copyright (C) 2021 Thomas Glau, DL3TG
+* Copyright (C) 2021-2023 Thomas Glau, DL3TG
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
@@ -108,7 +108,7 @@ static void aprs_pico_initClock(unsigned int sample_freq_in_hz)
  * \param[in]      pcm_data           The PCM audio samples to be rendered
  * \param[in]      num_samples        The number of PCM audio samples to be rendered
  * \param[in]      volume             The volume level of the generated AFSK signal (0 ... 256)
- * \param[in]      is_loop_forever    If 'true', the rendering of the audio samples will be continuously repeated
+ * \param[in]      is_loop_forever    If 'true', rendering of the audio samples will be continuously repeated
  */
 static void aprs_pico_renderAudioSamples(audio_buffer_pool_t* audio_buffer_pool, const int16_t* pcm_data,
                                          unsigned int num_samples, uint16_t volume, bool is_loop_forever)
@@ -116,24 +116,25 @@ static void aprs_pico_renderAudioSamples(audio_buffer_pool_t* audio_buffer_pool,
   assert(audio_buffer_pool != NULL);
   assert(pcm_data          != NULL);
 
-  unsigned int pos   = 0u;
-  bool is_keep_going = true;
+  unsigned int idx_src       = 0u;
+  bool         is_keep_going = true;
 
+  // Write the PCM sample data into the audio buffer(s) while applying the 'volume' value
   while (is_keep_going)
     {
-      audio_buffer_t* buffer  = take_audio_buffer(audio_buffer_pool, true);
-      int16_t*        samples = (int16_t*)buffer->buffer->bytes;
+      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 i = 0u; i < buffer->max_sample_count; i++)
+      for (unsigned int idx_dst = 0u; idx_dst < audio_buffer->max_sample_count; idx_dst++)
         {
-          samples[i] = ((int32_t)volume * (int32_t)pcm_data[pos]) >> 8u;
-          pos++;
+          audio_buffer_pcm_data[idx_dst] = ((int32_t)volume * (int32_t)pcm_data[idx_src]) >> 8u;
+          idx_src++;
 
-          if (pos == num_samples)
+          if (idx_src == num_samples)
             {
               if (is_loop_forever)
                 {
-                  pos = 0u;
+                  idx_src = 0u;
                 }
               else
                 {
@@ -143,8 +144,8 @@ static void aprs_pico_renderAudioSamples(audio_buffer_pool_t* audio_buffer_pool,
             }
         }
 
-      buffer->sample_count = buffer->max_sample_count;
-      give_audio_buffer(audio_buffer_pool, buffer);
+      audio_buffer->sample_count = audio_buffer->max_sample_count;
+      give_audio_buffer(audio_buffer_pool, audio_buffer);
     }
 }
 
@@ -176,34 +177,36 @@ audio_buffer_pool_t* aprs_pico_init()
 
 
 // See the header file for documentation
-void aprs_pico_send1kHz(audio_buffer_pool_t* audio_buffer_pool, uint16_t volume)
+void aprs_pico_send_sine_wave(audio_buffer_pool_t* audio_buffer_pool, unsigned int 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
-  unsigned int sample_freq_in_hz = APRS_PICO__PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ;
+  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;
 
-  aprs_pico_initClock(sample_freq_in_hz);
+  typedef int16_t wave_table_value_t;
+  const wave_table_value_t WAVE_TABLE_VALUE_MAX = INT16_MAX;
 
-  const unsigned int TONE_FREQ_IN_HZ = 1000u;
-  const unsigned int num_samples     = sample_freq_in_hz / TONE_FREQ_IN_HZ;
 
-  int16_t* sine_wave_table = malloc(num_samples * sizeof(int16_t));
+  aprs_pico_initClock(SAMPLE_FREQ_IN_HZ);
 
-  if (!sine_wave_table)
+  wave_table_value_t* sine_period_wave_table = malloc(num_samples_per_period * sizeof(wave_table_value_t));
+
+  if (sine_period_wave_table == NULL)
     {
       panic("Out of memory: malloc() failed.\n");
     }
 
-  for (unsigned int i = 0u; i < num_samples; i++)
+  for (unsigned int i = 0u; i < num_samples_per_period; i++)
     {
-      sine_wave_table[i] = (int16_t)(32767.0f * sinf(2.0f * (float)M_PI * (float)i / (float)num_samples));
+      sine_period_wave_table[i] = (wave_table_value_t)((float)WAVE_TABLE_VALUE_MAX * sinf(2.0f * (float)M_PI * (float)i / (float)num_samples_per_period));
     }
 
-  aprs_pico_renderAudioSamples(audio_buffer_pool, sine_wave_table, num_samples, volume, true);
+  aprs_pico_renderAudioSamples(audio_buffer_pool, sine_period_wave_table, num_samples_per_period, volume, true);
 
-  free(sine_wave_table);
+  free(sine_period_wave_table);
 }
 
 

src/aprs_pico_example.c

@@ -1,6 +1,6 @@
 /*
 * Project 'raspi-pico-aprs-tnc'
-* Copyright (C) 2021 Thomas Glau, DL3TG
+* Copyright (C) 2021-2023 Thomas Glau, DL3TG
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
@@ -31,9 +31,10 @@ int main()
 
 #if (SINE_WAVE_TEST == 1)
 
-  const uint16_t VOLUME = 128u;
+  const unsigned int FREQ_IN_HZ = 1000u;
+  const uint16_t     VOLUME     = 128u;
 
-  aprs_pico_send1kHz(audio_buffer_pool, VOLUME);
+  aprs_pico_send_sine_wave(audio_buffer_pool, FREQ_IN_HZ, VOLUME);
 
 #else // !SINE_WAVE_TEST