5761 Trigger Leads Analog CH 0 by 10.16 usec

Hi LV Developers,
I am having a bit of a headache here working with my FlexRIO. I have a 5761 AC Coupled Digitizer connected to a 7954r FPGA. All of this is mounted on a PXI Chassis 1031DC and I am running the system remotely through Ethernet. I am trying to do someting that is very simple: Use the SYNC output of my Agilent 33220A function generator to Trigger the TRIG line of my Digitizer in order to collect the waveform coming out of the function generator for a pre-specified amount of time on Channel 0. My code searches the TRIG line for a rising edge and once it detects it, it collects "X" amount of samples at a rate of 250 MHz until these "X" samples add up to the pre-specified sampling duration shown as "Record length in microseconds" on the screenshot below. Everything works well, and I can even get this system to trigger on falling edges. The problem is that the SYNC line is not in phase with my Output line when I record these. My Output line from the function generator seems to be leading the Sync line by 10.16 usec. Ideally, the SYNC lines becomes a TTL high (3.46 V) when the Ouput voltage is greater than zero.
Attachments:
Trigger Input 1 Waveform.zip ‏3864 KB

The lead actually depends on the frequency of the Output signal coming out of the function generator. I have found the following table:
frequency            Output lag in Sample points
5MHz            19 samples (@250Mhz Sample rate)
10MHz          9 samples
20 MHz       5 samples
and this is as high as my function generator can go. I plan to use this FPGA code to run a 10kHz signal.....so extrapolating the graph, I think I may be several hundred of samples out of phase.

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ich versuche eine Messung mit einem analogen Eingangssignal zu starten und zu beenden. Ich benutze die Messkarte NI-USB-6251. An Eingang ai0 ist ein Sinus-Signal angeschlossen. An Eingang apfi0 ist der Triggereingang angeschlossen. Das Triggersignal löse ich immer per Tastendruck auf dem Funktionsgenerator aus. Hier ist ein Teil des Quellcodes:
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int32 read;
float64 *data;
float64 sampleRate = 1000; //Samples per Channel per Second
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double triggerLevel = 2.0;
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Ich habe die Sample Rate (1000/s) und die Samples pro Kanal (4000) so gewählt, dass die Aufzeichnung 4 Sekunden dauert. Ich schaffe es auch die Aufzeichnung über den Trigger zu starten, jedoch funktioniert das Stoppen mit der Funktion DAQmxCfgAnlgEdgeRefTrig nicht. Aktuell ist es so, dass das Array immer mit 4000 Werten gefüllt wird.
Ich hatte mir erhofft, dass ich durch einmalige Triggerung die Messung starten kann und beispielsweise nach zwei Sekunden erneut triggere und die Messung damit stoppe und dann nur 2000 Werte eingelesen habe.
Ich hoffe, ihr könnt mir dabei helfen.

Hi Martin,
I looked over your code and noticed that you called the function without checking the returnvalue.
Try to change the line to the following:
First: define a new int32 value and call it for example: errorcode
Second: The function returns a status code, wich if it fails, includes an error code so save this code in the new generated value
errorcode = DAQmxCfgAnlgEdgeRefTrig (taskHandle, "/dev1/apfi0", DAQmx_Val_RisingSlope, triggerLevel, 3000);
and try to run the programm and read out this value.
If you got this value, please post it here and I will try to help you if I can.
Regards
Philipp

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Attachments:
use external A quad B singal as daq trigger.vi ‏57 KB

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Attachments:
Rotary.vi ‏213 KB

Never mind after looking at it somemore i found i was using the wrong sample rate

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poczatek.vi ‏124 KB
poczatek.vi ‏124 KB
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Attachments:
RC001 v_1.vi ‏49 KB

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===If this fixes your problem, mark as solution!===
Attachments:
RC001 v_1mod.vi ‏25 KB

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the error:
could you help me?
Thanks a lot!

You set your task up to run at a rate of 2400 samples per second, and request 64 samples to be read. This means that it will take at least 37.5ms to take the data.
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Output Side:
amplitude = 1
freuency = 50kHz
Sampling Frequency = 1MHz
3 of Samples = 200
Input Side:
Input Buffer 4000
trigger type = analog
pretrigger = 5
edge or slope = rising
scan rate = 500kHz
# of scans = 2000
Conditional Retrieval
mode = on
slope = rising
skip count = 0
level = .1
offset = 0
hysteresis = 0
So what we want to do is capture the ten
cycles of the 50k output pulse on the input and need to store that so we can plot it later, do you have any suggestions. we are using the PCI-MIO- 16E board.
Thanks,
Jarrod
Attachments:
InputOutput2.vi ‏88 KB

1) Toss the sequence frames (no flames please).
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3) After the output, go back and read the data that is waiting for you.
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End of Ben's suggestions for now.
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5761 Trigger Leads Analog CH 0 by 10.16 usec

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