Using Value as trigger??? USB 6221

[Leee]

Hi everybody,

I have a problem. I have 8 DO and 8 AI and I want to record my AI but I want to start recording at a specific point. For example of an rising edge of my signal which should at least reach 4 Volts. Is this possible and how to do it.

Another question is I want to know how long it is going to take my device to send out a signal and when I can receive it ( I connected DO with AI). Hoiw can I accomplish this test.

thanks for answering

[Kobi_K]

Hi,

1.Before you can set the trigger use for the channel settings

DAQmxErrChk (DAQmxCfgSampClkTiming(g_AItaskHandle,"",g_d_AIFreq,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,g_i_NumOfSampelsToRead)); 

2.This is for the trigger....

DAQmxErrChk (DAQmxCfgDigEdgeStartTrig(g_AItaskHandle,g_c_triggerSource,g_i_triggerEdge));  

3.This function will give you retrigger option....by the g_c_triggerSource ( Digital Soruce )

DAQmxErrChk (DAQmxSetTrigAttribute(g_AItaskHandle,DAQmx_StartTrig_Retriggerable,1));  

Hope it helps...

[Leee]

Hmm,

my Do and Ai are synced. They are using the same clock. So how do I tell my record that it should start recording when it sees a value over 4 volts.

[Philipp_Kost]

Hi Leee,

you only need to place the triggerfunction before the start function.

You can see it in several examples fron the LabVIEW-Examples library like the Acq&Graph Voltage-Int Clk-Retriggerable.vi.If you use an analog Edge, you can choose a channel and and a level for this function to start.

Regards,

Philipp

AE | NI Germany

[Kobi_K]

DAQmxErrChk (DAQmxCfgDigEdgeStartTrig(g_AItaskHandle,g_c_triggerSource,g_i_triggerEdge));

youer DO needs to be read by onw of the DI in the decive then g_c_triggerSource is your DI and g_i_triggerEdge is falling or rising.

when youer seeting this function it's basiclly saing the device when you aquice and DI falling q rising start the g_AItaskHandle Task.

as Philipp said you can use alot of exmples from ni help center or the cvi examples and they will be very helpfull

[Philipp_Kost]

I'm sorry.

I haven't watch the toppic of this thread.

But there are almost the same functions in CVI like Kobi has mentioned.

Regards,

Philipp