Write and test UART, SPI and I2C driver software for openPLC (running in ARM processor on Raspberry Pi (pi-pico, pi3, pi4, pi5), Stem32, MSP 430 etc.) to use with various items such as RYLR998 UART Interface 868/915 MHz Lora Module or AD 9364 module or Ublox M10 module or with iridium 9603.
OpenPLC drivers are located on OpenPLC_v3/webserver/core/hardware_layers. Take one of these files as example to build yours. It is written in C.
If you're using the GPIO pins for UART, make sure that the pins you're using for UART (TX and RX) are not being used by other functions in your WiringPi setup. You can configure the pins in your WiringPi code to avoid conflicts.
Following links may be helpful:
https://openplc.discussion.community/post/solvedproblem-to-connect-with-arduino-uno-and-generic-modbus-rtu-10489043
https://github.com/kinsamanka/openplc-stm32-freertos/blob/master/src/uart_task.c
https://openplc.discussion.community/post/studies-project-openplc-on-raspberry-and-arduinos-on-modbusrs232-11359207
Let's discuss this first before I can award this project to you!