rs232 cable

[pilulkin]

Hello!

I've been writing a program to communicate with TTi  1705 programmable multimeter and unfortunately, there is a catch: TTi says that I should use RS232 interface with XON/XOFF or NONE handshaking to communicate with PC or others controllers…

Communication settings

baud -9600

parity- none

handshaking- XON/XOFF /NONE

data bits-8

So, if I'm using regular RS232 cable it isn't working (with XON/XOF or NONE)-I just can send commands and there is no answer despite that DDM implement commands , if I'm using RS232 with only 3 physical  wires (TXD,RXD,GND )it's working well. Can I get your advice how to solve this issue?

[Dennis_Knutson]

I don't understand exactly what you are saying. You say there is no answer but in the next sentence, you say it is working well.

XON/XOFF handshaking is a software method so a 3 wire cable (if wired correctly) will work. Verify what the instrument is set to and then set your code to match. I would also suggest using a terminal emulation program such as Hypertermina, Procomm, Putty, etc. to check basic communication before writing a program.

[pilulkin]

Hi Dennis!

I mean that if I'm using RS232 cable made by me  with only 3 wires it's working well, with another standard cables it does't work. The same thing happens with Hyperterminal- with my cable it works well- I can communicate with device, with  another cables there is no responce.

In any case, thanks for the answer )))

[_Xilinx_]

The other lines in your cable are DTR & RTS, those are only needed for hardware handshaking.

I think you have the hardware handshaking turned on in some way in the software.

OR

If you use a custom made cable it's possible TX/RX (pin 2/3) are straight (ping 2 -> pin2 ) and not crossed (pin2 -> 3 and 3 ->2, GND=5), that might be the reason it's not working.