I have checked the spec, the MCU board has a RS232 compatible IC (TSC232), and the device i would like to communicate, is a printer that has the following structure:

The printer has a DB-25 port:
TXD - 2
RXD - 3
RTS - 4
CTS - 5
GND - 7
DCD - 8

it comes with a cable that convert DB-25 to DB-9(PC)
RXD - 2
TXD - 3
CTS - 8
DCD - 1
GND - 5
DTR - 4
DSR - 6

and i have tried to connect the MCU's RX to Printer's TX, and vice versa, but they are still not working. Is there any problems? The spec for the printer has just the layout of the cable.