Yes, I use now USB-UART from FTDI. But I not enjoy it and look at the patch https://github.com/raspberrypi/linux/co ... d3383eb1f3.I guess you won't get this with the Pi's native UARTs due to the lack of hardware RS485 support. Handling RTS in software is obviously not enough for you.
Alternatives:
1. Use USB-UARTs like FT4232H etc. They can be programmed to provide a driver enable signal hthat is generated in hardware.
2. Use NXP SC16IS1762 SPI-UARTs. They also have hardware RS485 support. I'm unsure whether the Linux driver can make use of this feature.
3. Use a small MCU like STM32C031 to handle the transceivers. This STM32's UART0 even has got a special MODBUS support to ensure correct intra-character spacing timing requirements. Use one MCU for each port. The Pi sends the Modbus request to the MCU, the MCU handles the request with the peripherial and returns the answer packet to the Pi. The Pi doesn't need to do anything timing critical then at all.
Statistics: Posted by YurgenGz — Mon Dec 22, 2025 12:42 pm