I am currently designing a standalone Proportional Valve curve tracer. In simple terms this is what it does :

1. The proportional valve command signals ( +/- 10V ) are generated by a MCU based on user programmed ramp rates. This is plot data #1.

2. Based on the command, the proportional valve reacts and issues a spool position feedback as (+/- 10 Volts) .This is plot data #2.

3. In a normal valve, plot data #2 will be a replica of plot data #1 but influenced by null offset and hysteris parameters. We have acceptance criteria for this.

4. This standalone unit will be interfaced to the PC via RS232 and running a VB front end for starting the test and plotting the values and other user interface controls. So far no problems.

To carry out the test start, stop it and the MCU reporting valve faults, I need a few control lines. If I use a 9-pin connection, I think I can get about 4 lines - RTS,CTS,DTR,DSR.

Question is, if I need a few more, can I use the secondary RTS, CTS etc of the 25 pin version. If so how many are available to me ? And whether all 25 pin serial ports support these ?

(I have till date just used the TXD and RXD pins. Never went beyond that. And the information on the net ( that I looked upon )is sketchy about the secondary pin functions. Hence the query)

Thanks

Raghu