triggering both edges of a TTL signal

[Adrian_Bradu]

Hi,

I am currently developing a program to acquire images via an external trigger on my 1428 board (I have got a function generator connected to deliver a TTL signal to the External trigger 0 on the 1428 board). Unfortunately, when using IMAQ Configure Trigger2 I have got only 2 options for polarity: falling edge OR raising edge. What I want it's to generate 2 images: when the TTL level jumps from low to high and also from high to low (i.e. for both polarities). Is there any way in which I can achieve this?

Thanks in advance for any advice/help you can provide.

Adrian

Univ of Kent, Canterbury, UK

[johnsold]

Adrian,

Can you set the function generator to twice the frequency and trigger on two successive rising edges?  If you need the original pulse for other circuits,  an external flipflop could derive that from the faster pulses.

Lynn 

[Adrian_Bradu]

Unfortunately I cannot double the frequency. I am basically looking for an elegant solution that doesn't involve any other external devices ...

Thanks for your message.

[StevenH]

Hi Adrian,

Unfortunately the 1428 only supports Rising OR Falling, not both.

Doubling the frequency of the pulse would have been a way around this.

Regards,

Steve