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  • Author Author: Jan Cumps
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Port Semtech LoRaWan Modem library to Pico: Pt. 1: Gather info and prepare development infra

Jan Cumps

The Semtch LoRa-node lib, that I used with some success in  Test LoRaWan Thing code ported for Raspberry Pico . is deprecated. It's replaced by LoRa Basic Modem.  I'm going to try and port that for the RP2040 controller. I've set ambitious goals:

  • don't change Semtech's code
  • port as specified by LoRa Basics Modem Porting Guide (30 pages of instructions)
  • use CMake, for compatibility with the Pico C/C++ SDK. Unless I find a way to integrate the make files in the build.
  • reusable for other projects

image
image source: Semtech Porting guide

Create a directory structure and get the LoRa Modem lib

I created a directory in the IDE workspace. I use VSCode, but the project works for any environment that can build one of Raspberry's Pico examples.

C:\Users\jancu\Documents\Pico\PicoSDKv1.5.1\workspace_1.5.1\pico_lorawan_modem

Then checked out Semtech's LoRa Modem lib:

git clone --recurse-submodules https://github.com/Lora-net/SWL2001.git

I created a main file, empty at the moment, and 2 CMake config files.

main.cpp

#include <stdio.h>
#include "pico/stdlib.h"

int main() {
    stdio_init_all();
    while (true) {
    }
    return 0;
}

CMakeList.txt

cmake_minimum_required(VERSION 3.13)

set(PICO_DEOPTIMIZED_DEBUG 1)

# Pull in SDK (must be before project)
include(pico_sdk_import.cmake)
set(PICO_BOARD seeed_xiao_rp2040)

project(pico_lorawan_modem C CXX ASM)
set(CMAKE_C_STANDARD 11)
set(CMAKE_CXX_STANDARD 20)

pico_sdk_init()

set(RADIO sx1276)
include (CMakeSWL2001.txt)

add_executable(${CMAKE_PROJECT_NAME} main.cpp )

pico_set_program_name(${CMAKE_PROJECT_NAME} ${CMAKE_PROJECT_NAME})
pico_set_program_version(${CMAKE_PROJECT_NAME} "0.1")

pico_enable_stdio_uart(${CMAKE_PROJECT_NAME} 0)
pico_enable_stdio_usb(${CMAKE_PROJECT_NAME} 1)



# Add any user requested libraries
target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE
        pico_stdlib
        )

pico_add_extra_outputs(${CMAKE_PROJECT_NAME})

This is a very common RP2040 file. You'll see that I only added two lines for the LoRa Modem:

set(RADIO sx1276)
include (CMakeSWL2001.txt)

That's because I plan to have anything related to the Semtech lib in a separate file.

CMakeSWL2001.txt

set(LORAWAN_LIB_NAME SWL2001)
add_library(${LORAWAN_LIB_NAME} INTERFACE)

target_include_directories(${LORAWAN_LIB_NAME} INTERFACE)
set(LORAMAC_LIB_PATH ${CMAKE_CURRENT_LIST_DIR}/SWL2001/lbm_lib)

if(NOT DEFINED RADIO)
  message("You must set a radio")
  message("set(RADIO <semtech radio model>")
  message("Valid options: (lr1110 lr1120 lr1121 sx1261 sx1262 sx1268 sx128x sx1272s) sx1276")
  message(FATAL_ERROR "Fix this before continuing.")
endif()
message("Radio selected: ${RADIO}")


target_sources(${LORAWAN_LIB_NAME} INTERFACE
#    ${LORAMAC_NODE_PATH}/src/peripherals/soft-se/soft-se.c
)

target_include_directories(${LORAWAN_LIB_NAME} INTERFACE
#    ${LORAMAC_NODE_PATH}/src
)

You can see it's still in its infant stage. It can manage a few things that I'll need later:

  • configure it so that the Pico example will see it as "one of the usual" libraries
  • check if a LoRaWan radio chip is selected. Error the build if not.
  • infra to collect all include and source files that 'll be required later.

image