DAQ assistant not detecting hardware

[sandeepchinni]

Hi Albert,

Thanks for the suggestion, but maybe why I did not think of it in the first place was, I am working on a remote system and I dont have anyone else sitting at the remote location!

What I was probably looking at was, is there a feedback loop mechanism by which I can verify that the pulses are being generated on the correct pins. Any suggestions?

Thanks,

Sandeep

[sandeepchinni]

Hi Kristen,

I executed the LL Trigger Drive.vi with various inputs and I got the following results.

1) When I had the trigger type as external and trigger number as 0 to 3 the program worked.

     I am assuming that this means that I can send signals to external devices through the pins 1 to 4 marked as TTL_Trig(0..3), is this correct?

2) When I had the trigger type as RTSI and trigger number as 0 to 6 the program worked.

     What does this mean?

In all other cases I got the error "NI IMAQ: The requested trigger line is invalid. Please verify that this trigger line exists and is properly connected to your device."

3) The trigger polarity field says that it drives the line(high or low) when the signal is true. Which signal is it referring to?

4) The trigger drive field is set to "Horizontal Synchronization Signal" by default. What does this mean?

5) And at last, do I generate pulses on the output lines periodicallt by placing the "IMAQ Trigger Drive2.vi" in a loop? or is done any other way?

Thanks,

Sandeep

[Kristen_K.]

Hi sandeep,

1) you are correct

2) the signal is sent to the RTSI lines on your card- you may not have a RTSI bus connected so it just goes nowhere, basically.

3) the signal it is refering to is the trigger - it allows you to set whether you want a high to correspond to true or low to correspond to true.

4) the "horizontal synchronization signal" is the signal that drives the trigger line.

5) generating periodic pusles will depend on the trigger drive.

This VI sends a trigger pulse to an external location based on camera events.  I would recommend looking at the NI-IMAQ VI Reference for more information about the IMAQ Trigger Drive2.  You can find this document by turning on context help, hovering your mouse over IMAQ Trigger Drive2, and clicking "Detailed Help" on the context help window.  

Kristen H.

[sandeepchinni]

Hi Kristen,

Thanks for the response. After going through the 1426 manual, I noticed one more thing regarding pins 7,8 and 14,15. It says that pins (7,8,14,15) "Alternatively, these pairs can be used as independent RS-422 trigger inputs instead of, not in addition to, TTL_TRIG<3..2>."

So, Does that mean I can send the trigger signals over these pins? And can I read the signals sent back on these pins, or can I read them only over the TTL pins(1-4)?

I am trying to connect the 15 pin D-sub port to a USB port on an external device and someone told me that using the RS-422 triggers would be useful in such a case. Please let me know your thoughts.

Thanks & Regards,

Sandeep

[Kristen_K.]

Hi sandeep,

 
The pins 7,8,14,15 can be used as RS-422 trigger inputs, but cannot be used at the same time as TTL <3..2> (pins 3 and 4).  The RS-422 is input only, so you will not be able to send a trigger on those lines. You are correct that you can only read through the TTL lines (pins 1-4).  In order to verify a trigger is sent, you can do a loopback test using the TTL lines.  The loopback test is done by wiring, for example TTL(0) [pin 1] to TTL (1) [pin 2].  You would then send a trigger through TTL(0) and read from TTL (1).  

Kristen H.

[sandeepchinni]

Thanks Kristen!

That finally gives me some idea as to how work with things. Now I need to find the last piece of the puzzle.

As I might have mentioned previously, I need to connect the PCI 1426 to a USB port of the GPS device. As you know the USB port has 4 pins, two data and two power pins. Since the 1426 doesnt have a power pin as such, can I have one of the 4 TTL line(1-4) continously at+5v high and connect it to the power pin(1) of the USB?

So, can my configuration be like this?

1426                 USB

pin1--------------pin1    Keeping the pin1 of 1426 continuously at +5v

pin2--------------pin2    For sending and receiving data

pin3--------------pin3    For receiving data

pin9--------------pin4    ground connections

Regards,

Sandeep

[Kristen_K.]

Hi Sandeep,

I would not recommend the configuration you posted for two reasons.  First,  USB requires encoding (NRZI convention, the wikipedia article on USB has a good description).  Second, providing a steady 5V to pin 1 will not necessarily provide the power required of the GPS device.  It may be possible to do (although I am not sure how you are planning on wiring it up), but is not recommended.  

Kristen H.