Pico Simple Test Not Working

[seykolla]

When I tried to save the image captured by simpletest.py for the Raspberry Pi Pico, I received a corrupted image. Additionally, setting the colorspace to jpeg mode doesn't return a memoryview object. Has anyone successfully captured an image on the Pi Pico?

[jerryneedell]

FYI -- I have been playing with the new PICOWBELL OV5640 board on a PicoW and I have found that for JPEG images, the captured image is often larger than the computed buffer so increasing the buffer size allows me to capture JPEG images.
With a too small buffer the EOI is not found int he buffer and the image is rejected.

[jmangum]

This might explain issues that I have been having with cam.capture(buffer) returning None. I have been chasing this issue with my PiCowbell OV5640 breakout running both with a RP2040 Pico W and RP2350 Pico 2W, but the behaviour was somewhat unpredictable. How much bigger does one need to make the computed capture buffer?

[jerryneedell]

This might explain issues that I have been having with cam.capture(buffer) returning None. I have been chasing this issue with my PiCowbell OV5640 breakout running both with a RP2040 Pico W and RP2350 Pico 2W, but the behaviour was somewhat unpredictable. How much bigger does one need to make the computed capture buffer?

It's been awhile since I looked at this, but in my code I had been using
jpeg_buffer = bytearray(cam.width*cam.height//5)

This was working better than the default "cam.width*cam.height//cam.quality" set in the library
https://github.com/adafruit/Adafruit_CircuitPython_OV5640/blob/main/adafruit_ov5640/__init__.py#L1239

[jmangum]

Thank you @jerryneedell . I have taken a slightly different tack and have simply scaled the size of the cam.capture_buffer_size by some amount, currently 10%:

scalebuf = 1.1 # Workaround for github issue 29 where computed
                           # buffer is too small to hold captured jpeg
capbuf = int(scalebuf*common.cam.capture_buffer_size)
#b = bytearray(common.cam.capture_buffer_size)
b = bytearray(capbuf)

So-far this seems to be working, but will monitor the IoT birdfeeder that this OV5640 is running on.

I should also note that I don't think that this issue is associated with the PiCowbell as I had in fact diagnosed the issue in December 2023 (and subsequently forgotten those tests...) with an OV5640 breakout wired to a proto board and running with a RP2040 Pico W. Posted my results to the CircuitPython forum at https://forums.adafruit.com/viewtopic.php?p=996457#p996457. Clearly the cam.capture function is cutting-off the JPEG file before it sees the EOI, as you noted.

[ladyada]

@jerryneedell can you submit a pr for that fix

[jerryneedell]

@jerryneedell can you submit a pr for that fix

Sure -- I'll dig out the hardware and do a bit more testing then submit it.

[jerryneedell]

@ladyada PR #35 submitted. Is this what you had in mind?

[jerryneedell]

@jmangum You had suggested 1.1 as the scale factor. I still ran out of room for some "quality" settings, but 2 may be overkill. Please comment on the PR is you think something in-between would be better.

As I noted in the PR, I don't think the PicoW is viable anyway and this is really targeted at the Pico2W
It works OK with a Pico

[jmangum]

@jerryneedell Agreed. I have a OV5640 breakout running with a PicoW but requires a lot of work (generous use of garbage collection to stay within memory limits). I don't have a better suggestion for the buffer size issue, but will try to do some testing to see there is a better algorithm for assigning a capture buffer that better matches the JPEG file requirements.

[ladyada]

tbh its never going to work well with picow, due to the wifi stack using so much ram. use the pico2 :)

[jmangum]

@ladyada I like the challenge!

[ladyada]

its a lot of work to save $1 🤷‍♀️