Userland service that runs on a Raspberry Pi and acts as a proxy between JMRI on TCP and a C/MRI network running over RS485. The need for this came about because half-duplex RS485 requires a control signal to toggle the transceiver between transmit and receive mode, which was proving difficult to achieve otherwise.
Starting the program with cargo run --release will start a TCP listener on localhost port 4000
There are two handy scripts - install.sh and uninstall.sh. The installation script checks that Cargo is installed and then compiles the binary and copies it to /usr/local/bin. It then installs ip_to_485 as a SystemD service to run at boot and starts it off.
Similarly, uninstall.sh stops and deregisters the SystemD service and removes the program from /usr/local/bin.
During development, a Pi 4 was connected to a MAX485 (with level shift divider on the RX side) and two arduino nano clones running a simple program based on ArduinoCMRI that provides a single sensor and single light.
The transceiver was wired to UART4, corresponding to GPIO pins 8 and 9, with the direction toggle connected to RTS4 on GPIO 11.
The following photos show the test setup:
Finally, here is a scope trace showing an incoming CMRI packet followed by the next CMRI poll. The top trace is RS485-A and the bottom is RTS:
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