Experimental Physics and
Industrial Control System

And if the frame arrives when I’m not waiting I need to know to send another trigger. 

 

Are you sure about that? That is not how I would expect that function to work. I would expect that is there is a frame available that you have not yet read it would return it to you.

 

Mark

 

Sent from my iPhone

On Jun 22, 2022, at 9:29 PM, David Vine <dvine at sigray.com> wrote:



The scheme you describe might be the best option. But it will miss a certain percentage of frames and I guess I’ll just have to work around that. 

 

On Wed, Jun 22, 2022 at 7:18 PM David Vine <dvine at sigray.com> wrote:

Yes but there’s a possibility the frame arrives when I’m not in that function. 

 

The polling loop would need to:

getIntegerParam(ADAcquire, &acquire)

If (acquire ==0) break

GevWaitForFrame()

 

And if the frame arrives when I’m not waiting I need to know to send another trigger. 

 

On Wed, Jun 22, 2022 at 6:46 PM Mark Rivers <rivers at cars.uchicago.edu> wrote:

Hi David,

 

Can you call GevWaitForFrame(timeout) with a short timeout?  If so then can’t that thread just poll with a short timeout. It should abort the polling loop if any of the following happens:

- It receives the frame OK

- It receives an abort signal

- It has been polling for significantly longer than the exposure time.

 

Mark

 

Sent from my iPhone

On Jun 22, 2022, at 7:04 PM, David Vine via Tech-talk <tech-talk at aps.anl.gov> wrote:



Hi all,

 

I wrote a driver for the Teledyne Shadobox 6k flat panel detector.

 

The API has a function called GevWaitForFrame(timeout) which must be being executed by the driver when a frame arrives from the camera or the frame will be missed. Are there any examples of a driver that has a similar API?

 

The problem is that it creates a race condition so if I execute the code sequentially:

 

send trigger

GevWaitForFrame(1 second)

 

It's possible for the frame to arrive before I'm "waiting" for it. Right now I have two threads that receive epicsEventSignal - one to send the trigger and one to wait.

 

That works ok but since I can't abort the GevWaitForFrame the driver gets out of sync for longer exposures. Eg I have a 5 second exposure so I set a 7 second timeout but then abort after 1 second my wait thread is stuck for 6 seconds.

 

I haven't had a camera API work like this before so any examples would be really helpful.

 

Thanks,

David

 

 

 

 

 

 

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