Problems getting RS232-Communication to work

Hello everyone,

in my current setup an external controller is sendingcommands to the MBL1660 every time the desired output changes, where xxxx stands for the desired power output level (open loop configuration).

I configured the external controller according to the data sheet (8 bits, 1 stop bit, no parity, 115.200 baud rate).

I checked and rechecked the RS232 wiring but nothing seems to work. A script running on my external controller converts the command into the ascII representation. I tried the above command with a carriage return and without (didn't know whether it was needed by the controller).

I was thinking that maybe the rs232 levels defined by each product aren't compatible. The Datasheet mbl1xxx.pdf says "RS232 I/O pins Voltage" is max 15 V. Does the mbl use -3..-15 V as 0 and 3..15 V as 1 (that's what the external controller uses I think)?

What else could cause the problem?

Thanks in advance and
kind regards
Felix

Perhaps, just wire the 2,3, and ground(5, or 13).