Problem connecting RS232 devices

[CWT52]

Hi Daniel,

Bill has made some valid points which are all correct. I have updated the code to include much of what he mentioned (i.e. enabled termination character, trim white space, remove wait functions, etc.).

Let me know if you have any further questions.

Cory

[Daniel_CB]

Hello again,

Thanks CWT52 for the file (which is very well organized and explained). I also would like to thank billko for the comments.

I used the vi in my pump and I was not able to control it.

--When I try to change the flowrate, I click on “write” and I track the procedure in the block diagram with the “highlight execution” mode. The vi runs without any error but the flowrate is not changed in the pump.

-When I try to read the current flowrate, the vi runs until the “VISA Read” icon, then it waits for some seconds (I asume that is the default timeout) amd then it finishes with the timeout error. (and of course, I don’t get any response string).

I wonder if the problem is somehow related with the pump. It seems to be "not pluged" at all. In that case, is there any way to test if the pump RS232 connection is activated (it is new). I mean, is there any way to make a “loopback” test to verify the ports of the pump?

Many thanks for all your help!

Daniel

[CWT52]

Hi Daniel,

Here are a couple of things I check on the hardware side when I'm having similar issues. You may have already tried these, but if not, they might be a good place to start. I realize there are probably other diagnostics you can run, but I'll let someone smarter than me advise you on that.

1) Check if the pump has a setting that enables/disables RS232 communications. Some devices require you to go enable this functionality.

2) Try a different RS232 to USB cable.

3) Try HyperTerminal, PuttyTel, or some other terminal to see if you can send basic commands (i.e. write set point, etc.).

Cory

[Daniel_CB]

Thanks for these recommendations.

I also don't have experience in this field. I will chech if someone in my department can help me with this and I will let you know the results!

Daniel

[Daniel_CB]

Dear all,

After several trials with different computers, cables, adaptors, different settings, using labview, putty etc... it seems the problem is related with the device. I will contact the technical support department and let you know any news.

Thanks a lot for your help!

Best,

Daniel

[Limhes]

I faced the same problem (Jasco PU-2080 RS232 communication) and just figured out what the problem is/was. I'll share it here for future reference.

The difficulty/problem is in the serial cable/connection. I figured out the correct connection by reverse-engineering the RS232 PCB inside the pump (all TH components, luckily).

For a DB9-female connection at the PC side and a DB25-male connection at the pump, the pinout is:

DB9 pin | DB25 pin

2 (RXD) | 2 (TXD)

3 (TXD) | 3 (RXD)

4 (DTR) | 6 (DSR)

5 (GND) | 7 (GND)

6 (DSR) | 20 (DTR)

7 (RTS) | 5 (CTS)

8 (CTS) | 4 (RTS)

I just made this cable, connected it via a standard USB-to-serial converter, and ran PuTTy at the recommended settings (4800 baud, 2 stop bits, no parity, 8 bit data, Xon/Xoff). Typing (without quotes): "a_flow load p" and then [Enter] immediately returns "0.000"

Happy pumping,

René