I'm using an UL865 connected to a microcontroller via UART with hardware flow control. Conencted signals: TXD, RXD, RTS, CTS.
Everything works fine at 115200, but I want to use 921600, so I change the baud rate appropiately with AT+IPR=921600 and establish the connection. PPP negotiation works and I have access to the Internet.
Now, I want to get the modem out of data mode in order to send it some AT command (hangup, for example). I'm completely unable to do this at 921600 baud. I send the <1s pause>+++<1s pause> escape sequence and nothing happens.
Note that this works perfectly when operating at 115200 baud rate. It's only when I set 921200 when the escape sequence doesn't work. BTW any baud rate above 115200 exhibits the same problem.
(need a way to get the modem out of data mode with just those four signals, resetting the modem is not an option in my case, deasserting DTE, which I've tried and works, is not either)