Multi sockets acquisition on 6259 lead to dummy data.

[yangyang-rexxar]

Hi

I have a 2 sockets parallel run sequence with only one DAQ card, everytime if I just run only one socket, the acquisition result is correct, but they are mostly wrong when the two sockets runs at a same time, the results are so far away from limits, I know this is caused by the two sockets manipulate the card at same time, but any way to solve it.

Thanks very much.

[Sam_Xu]

What do you mean by multi-sockets. You can not place two tasks in one programme if there is only one DAQ card. So why do not you create two channels for a single task?

[yangyang-rexxar]

Hi Sam

Multi sockets means I use parallel model for 2 UUTs, socket0 utilize 0-7 channel, socket1 utilize 15-22 channel, there are often some data acquistion steps who has dummy data, for instance, a limit between 3V-5V, but the result shows 0.1V.

[~jiggawax~]

Hi paulbin,

Are you using the default parallel model?  If so then are you making sure that the code modules you are calling are receiving the correct information regarding the different channels they need to access when doing the DAQ communication?  I don't know enough about DAQ but I'm sure if you are using DAQmx that you can multithread.  There is an example of it contained in the zip file here: http://zone.ni.com/devzone/cda/epd/p/id/840 

Things to be careful of would be resource locking (make sure you are doing it, look at the TestStand examples for info on that), information sharing (are the right values at the right place and at the right time, i.e. in testsocket 1 you need channels 0-7 and in testsocket 2 you need channels 15-22), DAQmx tasks (Are you using the same task for both threads or is each thread using a new task? if so then is this valid in DAQmx? again I don't know much about DAQmx) 

Regards,

Message Edited by Sam R on 09-07-2007 09:59 AM

[yangyang-rexxar]

Hi Sam R

I am using customized parallel model but just a little changes from original.

Every step of LabVIEW code to access DAQ dose open a new task and close the task when finish the step, and the driver is DAQmx, NI said it is multithreading safe, but I still need to lock the DAQ access blocks otherwise the card often crush.

But now I have locked related blocks regardless it is DAQmx, the sequence is better. The same case happen at serial port, if one socket have a long time reading of RS232A, another socket often has error, when I reduce the timeout time from 5 to 1, the serial ports are better than before, but still has error sometimes, I guess the two serial port has only one controller chipset:).

Another case is the DMM read step type can often not get value, see attachement.

Thanks very much. Sam