Re: PCI-DAS4020/12 external triggering?

On Wednesday 20 June 2007 09:11, Assar Westman wrote:
> Hi
> I have just begun to use the comedi lib as the Linux driver for a
> Measurement computing PCI-DAS4020/12 AD card. So far I have gotten
> the card initialized and samples are taken, but the problem right now
> is how the external trigger should be set up. I am using the BNC
> connector on the backplane on this board and it seems to trigger but
> the data I get is time skewed compared with what I see with a
> oscilloscope. I have been looking into the driver code and have seen
> that you should be able to change if the trigger should occur on a
> positive or negative flank,

You want to bitwise-or the start arg with CR_INVERT to get falling edge.  
Really you should do CR_EDGE too for edge triggering, but the driver 
doesn't actually care.

> and also the trigger level should be 
> possible to change between 0 or 2.5 V but I have not found how this
> should be done through the API and I am not sure what the default
> values are.

The driver doesn't support the board's analog triggering or hardware gating 
capabilities.

-- 
Frank