Is imgSessionTriggerRead edge sensitive or can you just read out a logic level

[Michiel Bronswijk]

Hello,

we are currently using an IMAQ PCI 1422 board connected to a CCD. In order to program this CCD we are using three of the external trigger lines to program the device in a serial way. External trigger #3 is wired as input data line from the CCD. I can successfully program the CCD, but I can not read back its response on External trigger #3.

I'm using imgSessionTriggerRead from the IMAQ library under Visual C++. The response on the scope we hooked up to our setup shows that the CCD gives the right data pattern back onto External trigger #3 but for some reason I do not get reliable read-outs using imsgSessionTriggerRead. Does this function only respond when the signal transitions from high to low or vice versa or can you directly read the current logic level of the trigger line. The help provided in the manual is a bit confusing.

Thanks in advance,

Michiel Bronswijk

[KvZ]

Upon return, the imgSessionTriggerRead sets status to a non-zero value if the trigger is asserted and to a zero value if the trigger is unasserted. So the function does not react to a edge.

As I understand you are trying to capture a digital pattern for your CCD then I would not recommend using a trigger line for this. The hardware is simply not designed to look for patterns. To work around this you will need to read the trigger line software timed and because of software jitter (and with Windows this can be in a range of 10ms) you will not get a accurate time base and can even miss pulses in your pattern.

you will need to use hardware that is able to do hardware timed digital input for the best representation of the pattern.

Hope this helps

Met vriendelijke groet / Kind regards,

Karsten
Applications Engineer
National Instruments