6251 digital trigger

[cek]

I am using the USB 6251 and attempting to use port 0 and 1 as digital outputs to trigger external hardware. I need to trigger the a/d to take x number of samples with an external start digital trigger and a external sample clock. Since I have "expanded" to using port 1, I can not get the a/d to trigger beyond the first set of samples. It also ignores using internal clock and no start trigger. Occasionally I also get bus over run error even though there were no samples taken.

Do I have a failed USB 6251 or can I not use anything beyond Port 0 digital control? Even if I strip out every thing except the a/d ( single channel) the device does not seem to accept external triggers. I can run test patterns and do both a/d and DIO and these work. But here to I occasionally get bus over errors.

CEK

[Neal M]

Hello CEK,

Your M Series card only has 8 lines of timed digital output (port 0) as seen in the 625x Specifications:


This is why you are unable to do correlated DIO on other ports. However I am supprised that you are not seeing errors all the time when you try to use port 1, I would expect LabVIEW to tell you what is going on.  Please see this knowledgebase for more information. Post back if you have any more questions.


Message Edited by Neal M on 01-21-2008 05:48 PM

[cek]

---

@cek wrote:
I am using the USB 6251 and attempting to use port 0 and 1 as digital outputs to trigger external hardware. I need to trigger the a/d to take x number of samples with an external start digital trigger and a external sample clock. Since I have "expanded" to using port 1, I can not get the a/d to trigger beyond the first set of samples. It also ignores using internal clock and no start trigger. Occasionally I also get bus over run error even though there were no samples taken.

Do I have a failed USB 6251 or can I not use anything beyond Port 0 digital control? Even if I strip out every thing except the a/d ( single channel) the device does not seem to accept external triggers. I can run test patterns and do both a/d and DIO and these work. But here to I occasionally get bus over errors.

CEK

---

---

@cek wrote:
I am using the USB 6251 and attempting to use port 0 and 1 as digital outputs to trigger external hardware. I need to trigger the a/d to take x number of samples with an external start digital trigger and a external sample clock. Since I have "expanded" to using port 1, I can not get the a/d to trigger beyond the first set of samples. It also ignores using internal clock and no start trigger. Occasionally I also get bus over run error even though there were no samples taken.

Do I have a failed USB 6251 or can I not use anything beyond Port 0 digital control? Even if I strip out every thing except the a/d ( single channel) the device does not seem to accept external triggers. I can run test patterns and do both a/d and DIO and these work. But here to I occasionally get bus over errors.

CEK

---

Hi Neal,

Good reminder, I did note that the higher order bits are not time correlated but after considerable time on the phone with one of NI's tech rep's we agreed that a/d conversion trigger was not functioning. We did guite a number of different SE and VI's to determine this. Thanks for your follow up.

CEK