configure handshakeline of serial port as powersupply

[rdam]

I need RTS/DTR line as supply for the optocoupler of a digital multimeter.
How can i configure my com-port to get the voltage (RTS -12V/DTR +12V)?

[Dennis_Knutson]

Check this other post from yesterday.

[rdam]

i checked the post, but how i have to configure the flow control? the rts line need a hardware handshake.

[PdB]

Don't be too sure the signal levels on RS-232 are +/- 12 Volt. In practice, aspecially on notebooks these voltages are way less. Also check that the popular RS-232 driverchips can actually be loaded by your power-circuit. When we designed a LabVIEW-controlled RS-232 powered external audio-mixer we learned by experience that the manufacturers not always comply to the RS-232 standard.

[JeanPierre]

Since the RTS and DTR lines are used to power the RS232 interface of the device, they can't be used for flow control. Configure the flow control of the port to "none" and after you set the state of RTS and DTR lines.

[rdam]

Hi Jean-Pierre,

i did it in the way wich you discribed. See the attached screenshot. But i don't get any strings from the device.

[JeanPierre]

Control lines are used to provide +/-12V to the device, one must be asserted and the other unasserted. Try both combinations. Usually, you provide the same polarity as HyperTerminal does when initialyzing the port.

[rdam]

Hi Jean-Pierre,

thanks for your help.
i tryed it in the way you discribed. but i dont get any strings. i attache the small labview file. can you see any mistake?

[JeanPierre]

That should work but without further info about your instrument, we can't figure what goes wrong. Have you been able to talk to your instrument with Hyperterminal?