Trouble with voltage of COM-port

[EdbO]

Hi folks,

I've got troubles to read data from the COM-port. To read data from the PCB (which controls a heatrecovery unit) we use the COM-port for the connection. Our vendor use the voltages on pin 4 and 20 to feed the PCB. When I start LabView I got -6,5V on pin 4 and 7,6V on pin 20. When I send the command "SBIM" (to readout the PCB) I got 7,4V on pin 4 and -6,9V on pin 20. After the timeout, the voltages are the same when I start LabView

The problem is that the voltages turn when I send a command and this does not may happen. Is there a property node or something where I can change this?

Thanks

Eddy

[Henrik_Volkers]

Check your flow control, since you (ab)use your hardware flow control lines. Shouldn't be set to hardware

Next: Set the state of DTE and RTS 'by wire' : drop the visa properties  node on your diagram and choose :modem line settings to set  the DTE and RTS line levels.

If you use a notebook you might get into trouble, sometimes the voltage level is to low to power circuits. Use a USB2RS232 cable in that case.