eespressif: ParallelImageCapture: keep peripheral running

[jepler]

Otherwise, a lot of frames were being dropped, leading to a low framerate in the "directio" demo for OV5640 cameras

Before:

After:

Note that as we're not doing anything to overlap the display write with the capture of the next frame, it's expected that 2 vsync pulses are needed for one display refresh.

[ladyada]

ok tested, it def cuts down on capture time, now 400ms instead of 600ms. still - why are we only able to get 4mhz pixclk? i feel like we should be zooming thru the data. and why does hqvga take the same amount of time as qvga??? so many ????!

[jepler]

Yeah, the OV5640 datasheet says we can do up to 120fps at 320x240, with a pixel clock of "24/48MHz". Clock/mode setting would need to be an issue filed against Adafruit_CircuitPython_OV5460. Adding background capturing would be an issue to add in the core first, then in the driver.