I have a board with UART, and an external converter to RS485. It sits at /dev/ttyS1. The converter requires that I put the UART RTS pin to high when sending and to low when receiving. I can achieve that by manipulating the pin from user-space before read/write calls, but I'd much prefer to have the serial driver do that. I follow verbatim the example in Documentation/serial/serial-rs485.txt, but what I get from
ENOTTY - not a tty device. How can I proceed to understand the issue?
$ ls -l /dev/ttyS1 crw-rw---- 1 root dialout 4, 65 Aug 29 09:16 /dev/ttyS1