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raspi-pico-aprs-tnc
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Split into lib + example application

main
eleccoder 2021-08-01 17:18:36 +02:00
rodzic 190667f82b
commit 906e390786
5 zmienionych plików z 186 dodań i 96 usunięć
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62
CMakeLists.txt
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@ -11,7 +11,7 @@ set(CMAKE_CXX_STANDARD 17)
pico_sdk_init()
# Setup of eleccoder's 'ax25-aprs-lib'
# (1) Setup of eleccoder's 'ax25-aprs-lib'
include(FetchContent)
FetchContent_Declare(ax25_aprs_lib
@ -24,30 +24,56 @@ FetchContent_MakeAvailable(ax25_aprs_lib)
add_library(ax25_aprs_lib::ax25beacon ALIAS ax25beacon)
# Setup of the application
# (2) Configure the library build
set(EXE_NAME aprs_pico)
set(TARGET_LIB_NAME aprs_pico)
add_executable(${EXE_NAME}
src/aprs_pico.c
add_library(${TARGET_LIB_NAME}
src/aprs_pico.c)
set_target_properties(${TARGET_LIB_NAME}
PROPERTIES
ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib"
)
target_include_directories(${EXE_NAME} PRIVATE
target_include_directories(${TARGET_LIB_NAME} PUBLIC
include
)
#target_compile_options(${EXE_NAME} PRIVATE "-Wall")
# Enable on demand
#target_compile_options(${TARGET_LIB_NAME} PRIVATE "-Wundef;-Wall")
# Set the console interface
pico_enable_stdio_usb(aprs_pico 1) # USB
# pico_enable_stdio_uart(aprs_pico 1) # UART
# create map/bin/hex file etc.
pico_add_extra_outputs(${EXE_NAME})
target_link_libraries(${EXE_NAME}
pico_stdlib
pico_audio_pwm
# This properly resolves the include dirs of the dependent libraries
target_link_libraries(${TARGET_LIB_NAME}
ax25_aprs_lib::ax25beacon
pico_audio_pwm
pico_stdlib
)
# (3) Configure the example application build
set(TARGET_EXAMPLE_EXE_NAME aprs_pico_example)
add_executable(${TARGET_EXAMPLE_EXE_NAME}
src/aprs_pico_example.c
)
target_include_directories(${TARGET_EXAMPLE_EXE_NAME} PRIVATE
include
)
# Set the console interface
pico_enable_stdio_usb(${TARGET_EXAMPLE_EXE_NAME} 1) # USB
#pico_enable_stdio_uart(${TARGET_EXAMPLE_EXE_NAME} 1) # UART
# create map/bin/hex file etc.
pico_add_extra_outputs(${TARGET_EXAMPLE_EXE_NAME})
target_link_libraries(${TARGET_EXAMPLE_EXE_NAME}
${TARGET_LIB_NAME}
ax25_aprs_lib::ax25beacon
pico_audio_pwm
pico_stdlib
)

23
README.md
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@ -6,21 +6,25 @@ An analog line-out audio signal will be produced at GPIO-pin 'GP0'. You can obse
Basically, this is the data/signal flow:
```
APRS (text msg + geo-coordinates + meta-data) -> AX.25 -> PCM -> PWM -> Low-Pass filtering -> AFSK signal
APRS (text msg + geo-coordinates + meta-data) -> AX.25 -> PCM -> PWM -> Band-Pass filtering -> AFSK audio signal
```
Both a static library `libaprs_pico.a` and an example application will be generated by the build.
## Preliminaries
Your host platform is assumed to be LINUX.
If you have already installed the Pico-SDK, set the `PICO_SDK_PATH` environment variable accordingly to avoid installing the SDK twice.
## Hardware
We just need a simple band-pass filter to extract the AFSK-signal from the PWM signal:
![band-pass filter](https://github.com/eleccoder/raspi-pico-aprs-tnc/blob/main/doc/schematic/band_pass_filter.png)
## Build the application
## Build the library and the example application
```
(cd into the cloned dir)
@ -28,28 +32,27 @@ cmake -S . -B build
cmake --build build
```
## Run the application
`build/lib/libaprs_pico.a` and `build/aprs_pico_example.xxx` will be created.
## Run the example application
```
cd build
(flash 'aprs_pico.uf2' or 'aprs_pico.elf' to the Pico board as usual)
(flash 'aprs_pico_example.uf2' or 'aprs_pico_example.elf' to the Pico board as usual)
```
The GPIO-pin 'GP0' is the line-out for the analog AFSK-signal. You can observe it by using 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).
![AFSK scope screenshot](https://github.com/eleccoder/raspi-pico-aprs-tnc/blob/main/doc/img/afsk_scope.png "Scope screenshot of an AFSK output signal")
## Modify the application
To send an APRS message of your choice, you have to modify the *main()* function in `src/aprs_pico.c`.
## TODO (Aug 2021)
- [x] Thorough evaluation
- [x] Thorough evaluation, in general
- [x] Send the APRS message on the console (USB or UART) rather than hard-coding
- [x] Code documentation
- [x] Show how to connect to a Baofeng HT
- [x] PTT control for HTs
- [x] PTT control for RF tranceivers
## Acknowledgements

44
include/aprs_pico.h 100644
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@ -0,0 +1,44 @@
/*
* Project 'raspi-pico-aprs-tnc'
* Copyright (C) 2021 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
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* 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 General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef APRS_PICO_H
#define APRS_PICO_H
#include <stdint.h>
#include <stdbool.h>
// 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
#define APRS_PICO__PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ (22050)
void sendAPRS(const char* call_sign_src,
const char* call_sign_dst,
const char* aprs_path_1,
const char* aprs_path_2,
const char* aprs_message,
const double latitude_in_deg,
const double longitude_in_deg,
const double altitude_in_m,
const uint8_t volume,
const bool is_loop);
void send1kHz(unsigned int sample_freq_in_hz, uint8_t volume);
#endif // APRS_PICO_H

105
src/aprs_pico.c
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@ -16,7 +16,8 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdbool.h>
#include <aprs_pico.h>
#include <stdio.h>
#include <math.h>
@ -26,21 +27,16 @@
#include <ax25beacon.h>
// 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
#define PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ (22050)
#define SINE_WAVE_TEST (0) // For test & debug
typedef struct AudioCallBackUserData
{
uint aprs_sample_freq_in_hz;
bool is_loop;
uint8_t volume;
unsigned int aprs_sample_freq_in_hz;
bool is_loop;
uint8_t volume;
} AudioCallBackUserData_t;
audio_buffer_pool_t* init_audio(uint sample_freq_in_hz, uint16_t audio_buffer_format)
static audio_buffer_pool_t* init_audio(unsigned int sample_freq_in_hz, uint16_t audio_buffer_format)
{
const int NUM_AUDIO_BUFFERS = 3;
const int SAMPLES_PER_BUFFER = 256;
@ -68,12 +64,12 @@ audio_buffer_pool_t* init_audio(uint sample_freq_in_hz, uint16_t audio_buffer_fo
}
static void init(uint sample_freq_in_hz)
static void init(unsigned int sample_freq_in_hz)
{
// 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
if (sample_freq_in_hz == PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ)
if (sample_freq_in_hz == APRS_PICO__PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ)
{
// This is the safe case, see the comment above
set_sys_clock_48mhz();
@ -83,7 +79,7 @@ static void init(uint sample_freq_in_hz)
// Compensate a non-'PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ' sampling frequency
// by a adapting the system clock accordingly
float sys_clock_in_mhz = 48.0f * (float)sample_freq_in_hz / (float)PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ;
float sys_clock_in_mhz = 48.0f * (float)sample_freq_in_hz / (float)APRS_PICO__PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ;
// Round to full Mhz to increase the chance that 'set_sys_clock_khz()' can exactly realize this frequency
sys_clock_in_mhz = round(sys_clock_in_mhz);
@ -96,9 +92,9 @@ static void init(uint sample_freq_in_hz)
static void fill_audio_buffer(audio_buffer_pool_t* audio_pool, const int16_t* pcm_data,
uint num_samples, uint8_t volume, bool is_loop_forever)
unsigned int num_samples, uint8_t volume, bool is_loop_forever)
{
uint pos = 0u;
unsigned int pos = 0u;
bool is_keep_going = true;
while (is_keep_going)
@ -106,7 +102,7 @@ static void fill_audio_buffer(audio_buffer_pool_t* audio_pool, const int16_t* pc
audio_buffer_t* buffer = take_audio_buffer(audio_pool, true);
int16_t* samples = (int16_t*)buffer->buffer->bytes;
for (uint i = 0u; i < buffer->max_sample_count; i++)
for (unsigned int i = 0u; i < buffer->max_sample_count; i++)
{
samples[i] = (volume * pcm_data[pos]) >> 8u;
pos++;
@ -131,13 +127,23 @@ static void fill_audio_buffer(audio_buffer_pool_t* audio_pool, const int16_t* pc
}
static void sendAPRS_audioCallback(void* callback_user_data, int16_t* pcm_data, size_t num_samples)
{
const AudioCallBackUserData_t user_data = *((const AudioCallBackUserData_t*)callback_user_data);
audio_buffer_pool_t* audio_pool = init_audio(user_data.aprs_sample_freq_in_hz, AUDIO_BUFFER_FORMAT_PCM_S16);
fill_audio_buffer(audio_pool, pcm_data, num_samples, user_data.volume, user_data.is_loop);
}
// Test tone: 1 kHz sine wave
static void send1kHz(uint sample_freq_in_hz, uint8_t volume)
void send1kHz( unsigned int sample_freq_in_hz, uint8_t volume)
{
init(sample_freq_in_hz);
const uint tone_freq_in_hz = 1000u;
const uint num_samples = sample_freq_in_hz / tone_freq_in_hz;
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));
@ -146,7 +152,7 @@ static void send1kHz(uint sample_freq_in_hz, uint8_t volume)
panic("Out of memory: malloc() failed.\n");
}
for (uint i = 0u; i < num_samples; i++)
for (unsigned int i = 0u; i < num_samples; i++)
{
sine_wave_table[i] = (int16_t)(32767.0f * sinf(2.0f * (float)M_PI * (float)i / (float)num_samples));
}
@ -159,26 +165,16 @@ static void send1kHz(uint sample_freq_in_hz, uint8_t volume)
}
static void sendAPRS_audioCallback(void* callback_user_data, int16_t* pcm_data, size_t num_samples)
{
const AudioCallBackUserData_t user_data = *((const AudioCallBackUserData_t*)callback_user_data);
audio_buffer_pool_t* audio_pool = init_audio(user_data.aprs_sample_freq_in_hz, AUDIO_BUFFER_FORMAT_PCM_S16);
fill_audio_buffer(audio_pool, pcm_data, num_samples, user_data.volume, user_data.is_loop);
}
static void sendAPRS(const char* call_sign_src,
const char* call_sign_dst,
const char* aprs_path_1,
const char* aprs_path_2,
const char* aprs_message,
const double latitude_in_deg,
const double longitude_in_deg,
const double altitude_in_m,
const uint8_t volume,
const bool is_loop)
void sendAPRS(const char* call_sign_src,
const char* call_sign_dst,
const char* aprs_path_1,
const char* aprs_path_2,
const char* aprs_message,
const double latitude_in_deg,
const double longitude_in_deg,
const double altitude_in_m,
const uint8_t volume,
const bool is_loop)
{
static AudioCallBackUserData_t callback_user_data;
@ -200,30 +196,3 @@ static void sendAPRS(const char* call_sign_src,
aprs_message,
'/', 'O');
}
int main()
{
#if (SINE_WAVE_TEST == 1)
const uint8_t VOLUME = 128u;
send1kHz(PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ, VOLUME);
#else // !SINE_WAVE_TEST
// Send an APRS test message
sendAPRS("SRC", // Src call sign
"DST", // Dst call sign
"PATH1",
"PATH2",
"Test message",
10.0, // Lat in deg
20.0, // Long in deg
100.0, // Alt in m
128u, // Volume (0 ... 255)
false); // Loop forever
#endif // SINE_WAVE_TEST, !SINE_WAVE_TEST
return 0;
}

48
src/aprs_pico_example.c 100644
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@ -0,0 +1,48 @@
/*
* Project 'raspi-pico-aprs-tnc'
* Copyright (C) 2021 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
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* 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 General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <aprs_pico.h>
#define SINE_WAVE_TEST (0) // For test & debug
int main()
{
#if (SINE_WAVE_TEST == 1)
const uint8_t VOLUME = 128u;
send1kHz(APRS_PICO__PICO_EXTRA_AUDIO_PWM_LIB_FIXED_SAMPLE_FREQ_IN_HZ, VOLUME);
#else // !SINE_WAVE_TEST
// Send an APRS test message
sendAPRS("SRC", // Src call sign
"DST", // Dst call sign
"PATH1",
"PATH2",
"Test message",
10.0, // Lat in deg
20.0, // Long in deg
100.0, // Alt in m
128u, // Volume (0 ... 255)
false); // Loop forever
#endif // SINE_WAVE_TEST, !SINE_WAVE_TEST
return 0;
}