Multi-platform (Arduino-free) library version of Philip Heron's ax25beacon project

This simple library generates the AFSK baseband audio tones for an AX.25 packet for use on the APRS (Automatic Packet Reporting System) network. It encodes position, altitude and an optional comment field.

Essentially, this is what a TNC (Terminal Network Controller) is doing in hardware.

Build the library

• All non-Windows platforms (for Raspberry Pi Pico, see down below for a special build configuration)

cmake -S . -B build
cmake --build build

• Windows (MinGW)

cmake -G "MinGW Makefiles" -S . -B build
cmake --build build

Run the example program (on targets w/ OS only)

cd build
./ax25beaconExample

Creates a aprs.wav file containing the AFSK audio tone encoding of an APRS test message. Decoding the original message can be done using the direwolf program:

cat aprs.wav | direwolf -r 48000 -D 1 -

Test Status

Platform	Arch	OS	Test Status
PC	x86_64	Ubuntu LINUX	✔️ Lib compiles & example runs
PC	x86_64	Windows 10 (MinGW)	✔️ Lib compiles & example runs
Raspberry Pi 3B+, 4B	ARMv7l/ARMv8	Raspberry Pi OS 32-bit	✔️ Lib compiles & example runs
Raspberry Pi Pico	ARMv6	none	✔️ Lib compiles

Special build configuration for Raspberry Pi Pico

Since this is a cross-platform build for an ARM target, you can't directly use the shipped CMakeLists.txt file, as it would perform a host build. Instead, you'll have to integrate the build of ax25-aprs-lib into the cmake configuration of your own Pico application in a manner like this:

cmake_minimum_required(VERSION 3.15)

# Copy this file from $PICO_SDK_PATH/pico-sdk/external
include(pico_sdk_import.cmake)

project(__YOUR_PROJECT_NAME_HERE__ VERSION 1.0)

set(CMAKE_C_STANDARD 11)
set(CMAKE_CXX_STANDARD 17)

pico_sdk_init()

# Setup of eleccoder's 'ax25-aprs-lib'

include(FetchContent)
FetchContent_Declare(ax25_aprs_lib
    GIT_REPOSITORY    "https://github.com/eleccoder/ax25-aprs-lib.git" 
    GIT_SHALLOW       ON
)

FetchContent_MakeAvailable(ax25_aprs_lib)

# Setup of the application

set(EXE_NAME __YOUR_EXECUTABLE_NAME_HERE__)

add_executable(${EXE_NAME}
    src/file.c
)

target_include_directories(${EXE_NAME} PRIVATE
    include
)

# 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
    ax25_aprs_lib::ax25beacon
)

Acknowledgements

• I've taken something from perplexinglysimple's pre-work
• I'm using brglng's libwav for the example program