On Thu, Apr 21, 2022 at 05:36:26PM +0200, Vicente Bergas wrote: > 2.- Although "linux,rs485-enabled-at-boot-time" is set in the DTS, > the RTS/DriverEnable line is asserted all the time the /dev/ttyS1 > device file is closed. > As soon as the device file is openned, the RTS line is deasserted. > Then it works as expected: it is asserted only during transmissions. > When the device file is closed again, the RTS line goes back to the > asserted level and stays there. > When the rs485 mode is enabled, it is expected that the RTS line be > deasserted by default. That's probably the same issue as reported here: https://lore.kernel.org/linux-serial/20220329085050.311408-1-matthias.schiffer@xxxxxxxxxxxxxxx/ Basically, some drivers have historically used inverse RTS polarity and others haven't. I'm still busy sorting out which drivers use which. Sorry, this is quite complex and takes some time. Have you configured "rs485-rts-active-low" in the device tree? Which kernel version are you using exactly? Thanks, Lukas
