serial remote transmission

[Identcor]

Hi,

I have a serial transmission between a NI system and another microcomputer using a cable working well, both computers are running a LabView application. When I tried to substitute this cable by a remote transmission (using a transmitter and a receiver modules) this communication stopped working well. Some of the data received is wrong.

I observed that the problem is in the transmission, that is, the wrong data received is introduced by the transmission, because I did these tests:

-Putting a computer running a MatLab application to perform the  transmission (not using the Labview application) and another computer running the receiving LabView application (using the transmitter and a receiver remote modules, not a cable) the transmission works well.

-Putting a computer running the transmission LabView application and another computer receiving the data using the Windows Hyperterminal (using the transmitter and a receiver remote modules, not a cable) some of the data received is wrong.

- Both computers using MatLab for the transmitting and receiving  applications (using the transmitter and a receiver remote modules, not a cable) work well.

If someone could help me I´d thank.

Celia

[chilly_charly]

If it works with a cable, there is no reason to believe that there is something wrong with your LV application. Have a look at the transmission rate, and switch to a much slower baud rate.

[Identcor]

Hi CC,

I've already done that (varying the baud rate) and it it didn't work.

Thanks,

Celia

[chilly_charly]

Few years ago, I had a problem with a poorly coded driver (not my work ;)) on a serial instrument. When hyperterminal was used to send data, everything was fine, but when LabVIEW was used, there were always transmissions errors. Of course everybody thought LabVIEW was the cause of the trouble. It wasn't. An undocumented delay of 0.1 sec was required between the transmission of each character, independently of the baud rate ! Of course typing in the commands with hyperterminal was fine...

In your case, everything works fine when you use a cable. And if you change the cable, you sometimes get errors. The wireless transmission introduces some kind of uncertainity in the connection. You could pick up random noise from a nearby source, possibly from your experimental setup. The fact that the transmission is working when using MatLab does not mean the problem is with LV. The problem is still will the transmission, but the way Matlab handles it is less prone to error with your wireles transmitter. 

What I would do is to write a short test program to send frames of the same character and check the reception to see if the problem is random or appears for some given chars. Try also  to insert a short delay between chars and see what happens.

Could you tell us the model of your wireless transmitter ? And the baud rate ?

[Identcor]

Hi CC,

I finally found a problem with my remote transmiter  hardware. There is a capacitor with a problem.

Thank you very much for your help.

Celia

[chilly_charly]

Good to ear that ! 🙂