rs232 RTS

[Graziano]

Hi everybody,
   I'm using LV 7.1 and RT module.

   My purpose is to use Digicom Modems LCM 16P with cFP-2020.  These modems should implement a point-to-point communication, between an embedded application running on cFP-2020 and a PC, running LabView application (for tests).

   I have to use 2 wires between the modems.  In this way, I have to perform Hardware flow control in RS232 communication, because, I suppose, the carrier signal should be on (over the 2 wires) only when device has to transmitt data.  I was told by Digicom to use RTS signal (pin 7 on DB9 connector).

   My question is: when I set VISA 232 property, what is the setting's choice? I mean, in flow control I can choose between
       -none;
      -RTS/DTS;
      -XON/XOFF;
    .....
 
   I build a simple test application in which I use RTS/DTS flow control type, but using my scope I observed that the carrier is always present on the transmission line, instead of beung present only during transmission.  In my test app, cFP-2020 sends data, PC receives data, so no overlapping is possible.

   When I set VISA properties for the modem, the carrier signal on modem goes up, and stops when I close (VISA close) the port.

   Suggestins wellcomed!!!

graziano

[James_R]

try using the property node and programaticly toggling the bits

[Graziano]

Hi James R,
   in fact that is my idea, but I was wondering if the "line toggling" can be automatic, I mean that when I perform a VISA write, the VISA function automatically performs necessary actions to:
    - check if device is not buisy;
    - request to send;
    - activate carrier signal;
    - transmitt;
    - at the end of transmision, deactivate carrier.

Bye!

graziano