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SAM S70 Image Sensor Interface synchro signals

Posted: Mon Jan 18, 2016 3:10 am
by MGen
Hi folks!

Has anybody experients with the ISI_VSYNC input signal's shaping here?

I have been capturing raw 12-bit pixels from a 1.3Mp sensor and sending through USB realtime. I have to capture the image line by line as full images (X * 1 sized image). Everything goes well, except that the code stucks at random time, random position (line number) etc. There are several symptoms.
I figured out (since 2 weeks now) that the VSYNC signal is the cause. I do my own VSYNC signal (by gpio) after a line has been transferred by DMA. But there is no details in the datasheet about the signal's timing (befeore/after HSYNC, pulse width etc.) I am currently trying almost all the possible pulse positions and widths and have found one that has been running for 27k frames now without fault. (Just some lost line (=my USB buffer full) but that's okay for the PC as host.) Other pulse configuration needs only some or some hundred frames to cause fault and they seem to depend on the USB host's activity too.

How or where can I be informed about that VSYNC signal? How to use it properly? What are the constraints?
It's annoying not to know why my code "works" or fails very rarely. :/