communication problem

Not sure what you're trying to do, but for devices to talk to eachother pins 2 & 3 need to "crossover" like this.

Device #1 Device #2 Connector #1 connector #2

pin #2 (transmit) pin #3 (recieve) pin #3 (recieve) pin #2 (transmit)

Staight cables (what you have) are sometimes used in special cases - like flashing EPROMs.

Not always the case, I spent 20 years in software and did RS232 stuff many many times and it all depends on how the maker wired their kit and whether they considered it DCE or DTE and what is at either end. RS232 comms probably causes more problems than anything I can think of. I've needed straight through on some applications, null modem?, and crossed on others, then of course if handshaking is added into the mix other signals may need to be added or pulled to an appropriate state to satisfy flow control.

But again, without knowing what the OP is trying to connect to what, there's no way to know how the cable should be pinned.

Hello djb, I am trying to get my software DeskCNC to communicate with a second generation controller for my cnc refit. I am a EE and have tried all i can think of trying a third computer setup presently. I was aware of the DCE and DTE differences even thru a 2 to 3 flip block in during testing. i am not sure if the software is getting to the port, i do have adjustment for he port number in the ini file but that has no guarantee function. im about to sell all this hardware and license on eBay and give someone else my money.

Thanks for your input

I'd insert a breakout box and watch the rxd and txd lines with a scope while trying to ping the controller with Hyperterm.

What does the controller expect for baud rate, parity, stop bits etc?

-jsw

"Jim Wilkins" fired this volley in news:mq60ji$50s$1 @dont-email.me:

AND DTE/DCE control signals and/or their 'strapping'.

It's JUST RS-232. If you can't make the controller respond, the first thing to do is put a terminal on the output of the computer, and see if it's sending anything...

And if you don't have a terminal or another computer to use as one (with a simple term like Hyperterm), then try a 'loopback test'.

Lloyd

Well, that's probably an EIA232 port, of the IBM 9-pin flavor. But the other end could be RS-422 (Macintosh style serial port), or RS-485, or have almost any pinout. So, have you looked at its quiescent voltages with a voltmeter? EIA232 input pins float around ground, and output pins are (+) when inactive. The data output pin on your 9-pin port on the computer is undoubtedly IBM-style wiring, TXD- is on pin 3.

If the controller has the same wiring as the computer, its pin 3 will have the same quiescent voltage signature, and a straight-through cable won't work. Null-modem cable is required.

Null modem?

I have a double ended USB cable with a module in the middle.

You plug it into the old computer and plug it into the new. If the two accounts are the same name, it copies everything like the old computer. New is ready to go like the old one.

I got it on Amazon as I recall.

Mart> >> Not sure what you're trying to do, but for devices to talk to eachother

It is a Easy Transfer Cable by Easy Computer Sync For Win 7, and later / vista/ xp.

Supports Window "Easy Transfer". No drivers needed. USB 2 to USB 2 Or a 3

Martin

If your computers are on a LAN You can use this freeby to do about anything you want with minimum hassle

The cable I mentioned transfers your 'old' account to your new computer. e.g. your email and everything. Doesn't transfer everything but gets you working on that end. Use the same username on both computers for it to work.

The LAN software is for small companies and common files for meetings...

Mart> >