Problem with serial read/write

[cirrusio]

Hello all,

I am not sure if this belongs here or on one of the hardware boards, but I thought I would start here.

I have two devices which I am currently trying to talk to via serial ports on a PXI chassis under real time.  In both instances, I have serial software that appears to be working fine when I use the serial port on the controller (i.e. COM1).  Now, I have two cards that I have been using on two different systems to talk to these devices - 8430/2 and the 8430/4.  In both instances, when I use these cards, it seems I have periodic delays in response by the devices when using the same code that I use when talking through the controller serial port (i.e. I get a time out on the attempt to read, error code -1073807339).  I have tried swapping the cards with spares but I get the same issue.  I can handle the delays by retransmitting the command, but this ultimately destroys the determinism of the system given that the delay can create a pause of up to about 2 seconds.  I have tried changing the buffer size but I seem to get the same problem.  Does anyone have any thoughts as to what might be going on?

Cheers, Matt

[-lucho-]

Hello Matt, hope you are doing great.

Seems to me what you are experiencing is a timeout error.

You can check this and let us know if it worked afterwards,

Warm regards Matt.

Luis Martinez.

Applications Engineer.

National Instruments. 

[cirrusio · Accepted solution]

Thanks, Luis.  Indeed, one of the errors being thrown was a timeout error (the other was thrown by one of the devices indicating that it did not understand the command sent).  However, the problem was not that I was getting a timeout, but rather that I was getting an error on one platform and not on another.  But, it seems that I have solved my problem - I simply set the VISA Write function I/O mode to synchronous and this seemed to fix the issue that I was having.

Cheers, Matt