Multi - counter and card of PCI 6602

[credo]

Hi All,
   I have 4 PCI 6602 cards in my PC,connected by RTSI cable.In the past I programmed them to count 32 channel in the same time.
After I look in deep details of Synchronize,I try to synchronize my board by set 1 counter on dev1 to the master trigger signal and route it to RTSI0
the in other counter use this signal to start Trigger of count.I also sent the master timebase from dev1 to others too.
  my code below is my first try to do as I mention above,but it found some error as in file below.

Please help to see my vi and comment
  I want 1 counter to generate signal to start trigger such as read every 5 seconds and send this through the RTSI to all dev.

Regards,

[Matt_A]

Hello credo,

The Start Trigger is not supported for Counter input operations. Instead, you would need to use the Arm Start Trigger. You can find a demonstration of this operation in the example program here. I also wanted to provide you with this example, which demonstrates how to program multiple counters for the same operation on the same device.

[credo]

Thank for your advice,I can sync it and arm it at the same time as attachment below
and I expand my project to share timing source and arm signal to other computer through PFI line

My project need 50 counter channel and I already have 4 PCI card then I need to buy another 3 card
It cheeper than but the new PXI systems
In master PC I send timing interval to slave PC through PFI line and inside each PC I connected RTSI cable to all card
and sahre master timebase.
Now I can start arm counter and stop on both computer at the same time

I think it's not actually sync between PC,but in 1 PC I'm sure it's sync.

I try to find the way to share master timebase between PC using output from RTSI cable or PFI line /Please help

[Matt_A]

Hello credo,

How are you connecting the PCI cards in the two different systems? At most, you can only connect 5 devices using National Instruments' RTSI cables and the longest cable is only a foot or so long. How are you able to connect 7 devices in 2 different computers?

You mention that you are sharing the arm start and stop triggers as well as the master timebase between systems. However, I believe you also said that you do not think that the acquisition is actually synchronized on both computers. Is that correct? Why don't you think both computers are synchronized?

[credo]

Hello Matt A
    Thank for youe mention,The reason that made me think both PC don't synchronize is They don't run on the same master timebase.
one PC share timebase between card,same to other,but they don't link to each other.They link only the timing source(I use to generate for acquistion period such as 2 second interval) and armstart signal through PFI line.but as I try in my lab both are start at the same time and can count the pulse signal from my generator in the same count value over 24 hrs.Or this is synchronized?

    If It can route 20 MHz timebase to RTSI line I will use some wire to connect this signal to RTSI pin on 1 card in other PC and I will route this timebase for sharing between card in that PC.

Regards,
credo

[Matt_A]

Hello credo,

If you share an arm start trigger signal between your two computers, then the start of your acquisition will be synchronized between the two. However, this does not synchronize the clocks onboard the devices. You may not need this level of synchronization as both systems will be running off their independent 20 MHz clocks. Depending on the width of the pulses you are trying to count, a 20 MHz clock may be enough to guarantee that you maintain the same count. In fact, I believe you mentioned that the two systems maintain the same count over a 24 hour period. This would indicate to me that your systems are synchronized within the necessary specifications for your application.

However, it is true that your application does not currently share the master timebase. If you would like to share the master timebase to synchronize both systems, you can export the signal to RTSI7 from the master system and import RTSI7 to the master timebase of the slave system. I have attached images of how your would export and import the signal.

One problem with this setup is that there will most likely be some delay between the master timebase signal on the master device and the signal that arrives at RTSI7 on the slave device. This delay can be attributed to the wiring you will have to use to connect the two separate systems. Additionally, depending on how you connect the systems, outside sources could induce noise on this clock signal that could affect the timing of your application. These are considerations that you will have to take into account if you choose to use the RTSI lines to route the master timebase.

Message Edited by Matt A on 07-09-2007 01:15 PM

[credo]

Thank you Matt, Now I  understand the use of DAQmx and counter card more than the beginning,I will try as your advice.Now I can route 20MHz timebase to RTSI7 with no error and can import RTSI to mastertimebase with no error in 1 PC,I will try to test on 2 PC and I think it will be fine with no error too.

Regards,
credo

[marconi 2042]

Hi Matt,

 

I am reading the post you and credo were discussing synchronize multi PCI 6602 card. Currently I am working on 20 PWM input channels. I have some problem on my labview code. Would you give some advice on my vi? I crated labview code for 2 channels for now. I am doing semi period measurement. I want to measure the frequency and duty cycle of the PWM signal. But when I run it, it has error. Please give some advice where I did wrong on my vi.

 thanks

Johnny

[Margaret F.]

Hello,

Thank you for posting to the NI forums. My suggestion is to take the read out of the for loop and run both reads in parallel while loops. You are bottlenecking right now because you have to wait on your slowest PWM. Running the reads in separate parallel while loops as well as reading more samples should fix the problem. Hope this helps!

[marconi 2042]

Hi Margaret,

 

Thanks for your advice, I tried your suggestion, it works. If I want to read 20 channels, so I need 20 while loops in parallel. Would that synchronize with other two PCI 6602 card?

 

Thanks,

 

Johnny