dear friends
i used 20 Opi zero with armbian 5.38 for communicating over ttyS1 to Megatec UPS devices
boards should send string on baud rate 2400 to UPS with RS232-To-TTL and get answer and work normally for the first time bur after a while serial stop transmitting data at all
restart , stop-start ,... not fix problems
the only way to fix the problem is connecting ttl to rs232 to pc and connect to serial with putty after that serial started send and receiving data and can use to communicate to ups devices
i faced this problems on 9 of 20 boards
programming language in python
Thank you in advance!