FieldPoint Family

Showing results for 
Search instead for 
Did you mean: 

cFP-2020 COM Ports 2 and 3 usage


I'm working on an application that needs to control multiple instruments through serial interface.


I'm able to control this instrument through COM1, but when I take the same instrument and try to control it from COM2 I don't have any communication.  In fact, so far I have not even gotten a simple loop-back test to work on COM2.


Is there a clever way to verify that COM2 is writing anything out to COM2?  I'm using a custom RJ45-10position for the FP end, to an RJ45-8pos at the power supply side, (but this end I have a TXD to RXD loopback)


I've included the simple test VI I'm using as well incase this helps anyone.


Thanks for any help or suggestions,


0 Kudos
Message 1 of 6

Hi Daniel,

   I've been using all cFP COM ports, they're almost equal.  Same config, same use.  Since I've not looked at your VI yet, I suppose 2 things: 


     1) Wrong cable connections, which lines you loop-backed? More, you should use a 10 pin connector, not an RJ45 (8 pin).  Somewhere, it is referred to as RJ50, but it isn't an official name.  I strongly suggest to buy a suitable cable from NI (10 position to DB9 cable).


     2) check, in MAX, if VISA is correctly installed, and if the cFP is seen as a 4 port module.  VISA file on cFP can be corrupted, I once encountered this problem.  There's also a possibility that if UART chip is damaged, port are not seen in configuration of cFP-2020.


   Hope this help!



0 Kudos
Message 2 of 6
Message Edited by Graziano on 10-02-2008 04:36 AM
0 Kudos
Message 3 of 6



I concur with Graziano that COM ports on cFP are identical.  I use them all the time in applications similar to yours with no problems.  I would doublecheck your cabling. 

Message 4 of 6

Thanks guys.


I did another loopback test and just kept trying different lines until I got a readback.  The cFP-2020 spec I read that had the RJ45-10pos pinout seems to have the pin numbers reversed.  The loopback test works, and as soon as I have access to the instruments again I'm sure the communication will work.


Sorry for the silly hardware troubleshooting post.


0 Kudos
Message 5 of 6



daniel_vi wrote:

The cFP-2020 spec I read that had the RJ45-10pos pinout seems to have the pin numbers reversed.

    ...what do you mean?!?!?!? Here's the data you need to build the cable (RJ50, or 10 position RJ, don't call it RJ45 Smiley Happy):


   cFP-2020 COM

   (From cFP-20xx User manual, april 2004 edition)


   So be careful to connect pin 9 and 8 to have a loopback, anc not 2 and 3 (okay unless you number from right Smiley Happy)!!!




Message Edited by Graziano on 10-03-2008 02:12 AM
0 Kudos
Message 6 of 6