For anyone who is interested here are the pinouts for an IBM compatible PC
COM Port along with their signal direction.
DB9 Male connector on PC
1 - DCD - Input
2 - RxD - Input
3 - TxD - Output
4 - DTR - Output
5 - GND
6 - DSR - Input
7 - RTS - Output
8 - CTS - Input
9 - RI - Input
DB25 Male connector on PC
2 - TxD - Output
3 - RxD - Input
4 - RTS - Output
5 - CTS - Input
6 - DSR - Input
7 - GND
8 - DCD - Input
20 - DTR - Output
22 - RI - Input
Notice how TxD and Rxd use pins 2 and 3 on both connectors but are reversed
between them, this is te reason you need to reverse them with an OMNI-VI!
I opened my OMNI up and took the DVM and checked into the TxD and RxD
signals. Tentec has pin 3 on the DB25F (RxD) going to pin 14 of the MAX232
TTL to RS232 chip, this is a transmit pin. Pin 2 on the DB25F goes to pin
13 on the MAX232 which is a receive pin. This means that they did the
TxD/Rxd swap inside the radio, therefore NO NEED to do it in the cable!
73,
Warren - N2BCC
wwalsh@intac.com
|