Hello,
I assume that you are referring to DB9 (9-pin) female connectors on both boards. If so, it is possible that both boards are configured as "data communications equipment" (DCE).
However, the use of a standard 9-way through lead assumes that the DCE device is connected to a "data terminal equipment" (DTE). A computer serial port is normally configured as a DTE.
For a DCE to communicate with another DCE (or for two DTEs to communicate), a special lead or adaptor is necessary. This is called a "null modem". You might purchase a null modem adaptor, or alternatively make your own null modem lead.
In the latter case, the data connections will need to be swapped, as a minimum. If hardware handshaking is implemented, other swapped connections may also need to be present.
End 1: End 2
TXD ----------- RXD
RXD ----------- TXD
RTS ----------- CTS
CTS ----------- RTS
DTR ----------- DSR
DSR ----------- DTR
GND ----------- GND
DCD No connection
RI No connection
Regards,
Mac
