Why the intial output of IMAQ1409 I/O trigger line is 2V?

[TNI]

I just turn on the computer and do nothing else, the intial output of the trigger line is about 2V, why? How can I intialize it to zero, I can't find any function to do that?
And I read the the Trigger, it is always true for IMG_TRIG_POLAR_ACTIVEH, so I can't do anything to trig.

[Yusuf C]

Hello,

The trigger lines have a pull-up resistor on them and 2V signal does qualify for a TTL logic high, which agrees with the software reads that return you a true value for active high polarity.
In order to write a low value you need to call ImgSessionTriggerDrive with an unasserted trigger drive mode.
Hope this helps!

Regards,

Yusuf C.
Applications Engineering
National Instruments

[TNI]

Thanks much!
1)According to what you say, the output of trigger line is high and nothing wrong with the grab card.

2)If I want to trig by IMG_TRIG_POLAR_ACTIVEH signal, what should I do? with clean 5v power or with pulse train?
3)I just trig in trigger line 0, why I can also get image through other trigger lines?

[TNI]

4)ImgSessionTriggerDrive with an unasserted trigger drive mode. After I use the IMG_TRIG_DRIVE_UNASSERTED, the output signal become more higher. If I use ASSERTED, it works, why?

[TNI]

While in the pulse generation, always a 2v signal line between the low and high of the pulse, how can I get rid of it?

Thanks.

[Yusuf C]

You probably need to switch your polarity.

[Yusuf C]

I'm not sure if I understand what you mean by getting rid of the 2V difference between a TTL high and a TTL low. Can you rephrase your question with more specific information please?

[TNI]

Thanks much!
The question is that I use pulse generate function (like PulseStart,etc) to generate pulses, as normal there should be just clean low and high line(while dispay by oscilloscope), but here what we get is another continuous line between these two lines, the line correspond to the initial output 2v.

By the way, what is you mean to change the polarity,how can I do that?