How to start serial instrument control with BOC Edwards Active Gauge Controller (AGC)?

[M_T]

I have been unable to establish serial instrument control using the rs232 option with a BOC Edwards Active Gauge Controller (AGC).  I have tried the BOC edwards ASCII commands ?AL and ?DP, as a try.  The termination character is set at 13 for carriage return and a line feed, as a start.  The BOC Edwards RS232 AGC manual, says information is transmitted with each line separated by CR LF.  The block is terminated by four characters: $ CR LF EOF (ASCII chars 36, 13, 10, 26/CTRL Z.  I maybe having confusion with the termination character settings.  I have used serial read/write.VI as a start.  I have troublshooted the computer's COM1 port and cables by successfully doing instrument control with a Keithley sourcemeter.

On the AGC controller, I have programmed the serial port settings to be the same as the computer's settings.  MAX shows that the COM1 port is working properly with the AGC connected.

I have also tried the NI instrument driver for TIC gauges with no success.  

Any suggestions?  

[M_T]

Additional information:

From the Boc Edwards manual.  "Each query or command is sent to the AGC via the RS232 serial link as a text message - a sequence of ASCII coded characters."

In the Labview VI, serial read write.  I used a termination character of a carriage return \r for the query,  "?dp\r".  Because in the BOC edwards instructions it noted the last character must be a carriage return (ascii char 13).

[Dennis_Knutson]

First, MAX does not verify that the com port is working with or without your instrument connected. All MAX does is say that the pc reports a serial port is present. Second, check a serial cable with one instrument does not mean it is the correct cable for a different instrument. There are two types - null-modem and straight-through. Try both. Third, try using hyperterminal before you try writing your own program. Get that to work and LabVIEW should be a piece a cake. Forth, verify that your termination character is actually the control code \n and not the separate characters '\' and 'n'. You need '\' Codes Display turned on for the control code. Lastly, the VISA Configure Serial Port does not do anything for a termination character on a write. It only sets up how to detect a character during a read.

[M_T]

Thanks.  I will be giving a crossover serial cable a try.    I reread the equipment manual and it mentioned that a crossover cable is required for direct computer attachment and a normal cable is required when connected to a modem. 

Again, thanks for the suggestions and troubleshooting procedure.