The Linux kernel has an RS485 mode for driving the RTS line, and that is set based on whether there is data to be transmitted rather than the FIFO fill level.
https://www.kernel.org/doc/html/latest/ ... rs485.html
If you want that mode, then you can tell the kernel so from device tree as well through the dtoverlay line in config.txt.
eg the overrides are documented for uart2 at https://github.com/raspberrypi/linux/bl ... 5235-L5250, but can also be viewed using "dtoverlay -h uart2" at the command line.
https://www.kernel.org/doc/html/latest/ ... rs485.html
If you want that mode, then you can tell the kernel so from device tree as well through the dtoverlay line in config.txt.
eg the overrides are documented for uart2 at https://github.com/raspberrypi/linux/bl ... 5235-L5250, but can also be viewed using "dtoverlay -h uart2" at the command line.
Statistics: Posted by 6by9 — Tue Jun 10, 2025 2:13 pm