Thank you for trying out the camera module and sharing your findings. We haven't had a chance to test with the OV3660, so your results are quite helpful!

All of the hardware configuration parameters for the camera are currently defined only in the manifest. For example, here is the manifest fragment for the Xiao Sense board:

		"camera": {
			"xclk": 10,
			"pclk": 13,
			"href": 47,
			"vsync": 38,
			"scl": 39,
			"sda": 40,
			"d0": 15,
			"d1": 17,
			"d2": 18,
			"d3": 16,
			"d4": 14,
			"d5": 12,
			"d6": 11,
			"d7": 48
		}

Since the xclk_freq_hz is also a hardware configuration property, it will be fixed for any camera. Therefore, I think it makes sense to also define it in the manifest, rather than in script:

		"camera": {
			"xclk": 10,
			"xclk_freq_hz": 20000000,
			"pclk": 13,
			...

Then in the camera.c implementation, add this near the top:

#ifndef MODDEF_CAMERA_XCLK_FREQ_HZ
	#define MODDEF_CAMERA_XCLK_FREQ_HZ (24000000)
#endif

...and change this line:

	.xclk_freq_hz = MODDEF_CAMERA_XCLK_FREQ_HZ,

If we want to make xclk_freq_hz configurable from script, then we should probably make all the hardware camera properties configurable. I'm not sure if is necessary right now, however.

What do you think?

@phoddie
Thank you for your response. It looks reasonable for me for instance.

In addition to your proposal, camera_config.jpeg_quality is also for configurable.

sensor_t config in ESP32-Camera repository is important for image quality, but not defined in camera.c
brightness, contrast, saturation, sharpness and denoise are parameters for image quality.
I think this is furthermore enhancement.

(sorry for the blog page in Japanese, but good information for the difference between OV2640 and OV3660)
https://intellectualcuriosity.hatenablog.com/entry/2024/03/21/215308

@kitazaki – Thanks for reviewing. I'll make the change to add XCLK_FREQ_HZ and JPEG_QUALITY options to the manifest.

brightness, contrast, saturation, sharpness and denoise are parameters for image quality.
I think this is furthermore enhancement.

Completely agreed. These are values that we will want to change at runtime, so they will require an API. @mkellner has started to investigate this already. My hope is to standardized the API as part of ECMA-419 (the current Camera API is already scheduled to be part of ECMA-419 3rd Edition).

...good information for the difference between OV2640 and OV3660)

Very nice piece. Thanks for sharing!