Hello, I'm having the same problem. I can't read any internal register as SC18IM704 starts responding before the message from the master is terminated with the 'P' character. I tried with 9600 and 115200 kbps, and it looked the same.
The identification message is working correctly, the "OK" message is transmitted after startup as well. Writing the internal register was obviously ok as well since I managed to switch the baudrate.
I tried to power SC18IM704 down, for checking the message from master and it was ok.
Can you please help me?
Thank you.
Tomas


