USB data transmission pauses

[E Murphy]

Hello everybody:

I´m using a DaqPad 6015 for USB and use an external trigger signal to start data acquisition. In some laptops, I have a problem of a pause  between readings and loose some data (vibration readings during a coastdown) On other laptops, data is acquired without the pauses. I have tried disabling Norton or other background programs but still I don´t get continuous readings.... any ideas?

Thanks

Eduardo Murphy

[Tania_Lozoya]

Hi E Murphy!

Are you doing a finite or continous adquisition? Does this problem also occurs when you are not using a trigger?  Have you tried to modify the samples per cycle to see if that has any effect?

What version of the driver are you using? Are you using LabVIEW (what version?)? Or using another software?

If you give me a little more of details, we can try with an example and reproduce the problem.

We also need to know if we are using the minimum system requeriments for the hardware and software, so we need to know what processor, RAM, OS, we are using in each laptop.

Also, are you using High speed USB ?

Tania Lozoya

NI MEXICO

Mensaje editado por Tania Lozoya

[E Murphy]

Hi Tania Lozaya:
Thanks for your reply.
We are doing finite sample acquisition at different sampling frequencies. Number of samples is constant.
We are using VB.NET
On our LapTop (Toshiba, Celeron, 2.4 GHz, 2004) we had some problems. We found out that resetting the DAQPad 6015 reduced the pauses. Recently we bought another DAQPad and noticed that the pauses were gone. Also, the problem seems cured with the older DAQPad (2004) We think that maybe it was because we recompiled our program (after some minor changes) Our client has a brand new HP LapTop (with widescreen) and we were supposing that he was not going to have any problems, but in fact, the pauses occur every 5 or 10 seconds and last about 2 seconds on that machine. No problem with our computer. We tried closing most of the background programs (NAV, Palm Synch, ...) but had no changes.
I don´t know if the USB ports are high or low speed. In my computer I checked the task administrator and one port shows a 10% bandwidth, whether the other one shows 11% (I have only to physical USB ports) I will try to determine the speed of the ports on my and my client's LapTop.
Regards
Eduardo Murphy
PD I have 256 k of RAM

[Tania_Lozoya]

Hi E Murphy,

Well if you are doing finite adquisitions, the pauses could happening between one fine adquisition and the next. Can we make a test a do an continuos adquisition, to see if the pause occurs during a continiuous adquisition. If this is the case, the problem could be in the board, if not, we can try something in software, maybe changing the samples to read in the finite adquisition, maybe we are using a large number of samples in every iteration. Can you tell me some of the samples to read, and the sample rate, is this in just one channel?

What version of the driver are you using?

Tania Lozoya

NI MEXICO

[E Murphy]

Hi Tania:

I´m gathering less than 200 samples i each finite acquisition. Sampling rate is less than 5 kHz. The new 6015 board works without pauses with my Toshiba LapTop (2004) and so does my old 6015 (2004) With the new HP LapTop, the new 6015 works with pauses, so I think the problem is with the computer and the USB configuration or it´s priority.
I´m using 8.0 NIDAQ
Regards
Eduardo Murphy

[Tania_Lozoya]

Hi!

Have you tried to use one of the shipping examples, like "Acq&Graph Voltage-Int Clk-Dig Start.vi"?

Have you tried to use a code without a trigger? To see if it has the same behavior.

This could be the USB connection, hter behavior is that after the trigger, adquires some samples, stops for a while, and then ends the adquisition? Just to see if I understood the problem, I'm checking my resources.

Thanks for you patience.

Tania Lozoya

NI MEXICO

[E Murphy]

Hello Tania:

I have tried on demand acquisition of samples and only get some trouble when trying to read more than 8000 samples at more than 50 kHz (2 channels) I have "solved" this lowering the number of samples.

With the triggered acquisition I first detrmine the speed (measure period) and then establish the sampling frequency. If I continuously read the speed, I have no problem. It is when speed and acquiring samples cycles that give the pauses.

Regards

Eduardo Murphy 

[Tania_Lozoya]

Hi!

Have you tried with one of the shipping examples?, so we have code in common, this model uses USB 1.1, it could be the USB connection, but to make sure, I would like to use the shipping examples, to see if you have the same behavior.

Tania Lozoya

NI MEXICO