capture to LVGL sample: ov5460 on a STM32H7a3zi

[josuah]

@CharlesDias I am trying to use the ov5460 on a STM32H7a3zi. Im using latest Zephyr master but I get
video_ov5640: Unsupported pixel format or resolution.

Is there any PR I need for this to run thats not yet in master? Or did I do something wrong? Im using the lvgl sample but removed all lvgl code as I dont have a display.

Originally posted by @CodingGhost in #74353 (comment)

[josuah]

Unsupported pixel format or resolution

The pixel format is selected by the application.
The application of the LVGL sample is supporting multiple hardware.
Each hardware support a different subset of formats.
To allow supporting all hardware, users might need to specify the format they wish to use. The one that matches their hardware.

You can do this with this Kconfig using a "fourCC" string such as one listed from here.
This option was introduced here:
https://github.com/zephyrproject-rtos/zephyr/pull/77879/files#diff-737bb0ca878e20bfaaf493aae9eb42d3de0e40e22a0fd17ac08d826050c1d41bR11

It is possible that this broke some other boards, for which the resolution was not specified.
If you wish to patch it upstream, you can add a line like this on a new board/stm32h7...conf file in the samples directory: https://github.com/zephyrproject-rtos/zephyr/tree/main/samples/drivers/video/capture/boards

CONFIG_VIDEO_PIXEL_FORMAT="RGB8"

Or in command line: west build ... -- -D CONFIG_VIDEO_PIXEL_FORMAT="RGB8" (I think).

With whichever format works with your particular display.
This sample does not the pixel format conversion (too slow with software), so you need to make sure the format chosen for the camera matches the one of the display.

Maybe it would be good to document that the user needs to select which pixel format to use between the display and camera...

If that does not work, we can continue the discussion here :)
Then depending on the outcome, we would know how we can patch it upstream.
Thank you for trying!

[CodingGhost]

@CharlesDias I did not change it, I dont even know how I can change it. Where can I set the Pixelclock? Maybe thats missing?
Is there anything I need to modify from the bare capture to LVGL sample because it originally doesnt use dcmi? I thought not because over at discord you posted that this sample can be used to test the ov5640 PR

[CharlesDias]

@CodingGhost , which board are ypu using? The PIXCLK depende on the oscillator used on ov5640 and some register configuration (I don't know which one).

You can meassure it using the oscilloscope or logic analyzer. Also, you can try to increase the AHB frequency.

[CodingGhost]

@CharlesDias Im using the Adafruit Ov5640 breakout on a STM32H7a3Zi-q. That makes sense, I thought the pixclk is generated by the Driver, but the pixelclock is generated by the camera, and the STM32 is just reading it. But wouldnt the ov5640 driver need to be able to set the Register for the Pixelclock speed? I will try to find out how I can change the AHB clock first though.

[CharlesDias]

@CodingGhost , check on the schematic of the board if it has a oscillator to ov5640 or if the clock came from the MCO microntroller pin.

To change the AHB frequency, you have to change the device tree configuration, nodes pll and rcc. You can use the STM32CubeMX to check the correct values or the research on datasheet. 😀

[CodingGhost]

@CharlesDias I have set a jumper on the camera board that is supposed to generate a clock for the cam. I guess thats what you mean? It also has the pxlclk pin, but if I understand correctly this pin is an output and not an input.
I will check what the clocks currently are to make sure that this is not the problem.

[CodingGhost]

@CharlesDias thanks for that Tip! I created one big sram partition and now I can use
CONFIG_VIDEO_BUFFER_POOL_NUM_MAX=2
CONFIG_VIDEO_BUFFER_POOL_SZ_MAX=262144

But the application still hangs, even though im only using 160x120.

[CharlesDias]

@CodingGhost do you have debugger and logic analyzer or oscilloscope?

[CodingGhost]

I have a debugger and a dso, I think I can use my dso with pulseview.

[CodingGhost]

@CharlesDias I checked the wiring again, and this time I found a jumper calbe with a loose connection. replaced it and it instantly works. damn it could have been so easy :D
thanks for all the help anyways! now I think I have to implement JPEG mode, do you have any hint with where to start implementing this?

[josuah]

where to start implementing this?

For the OV5640, the datasheet is exceptionally available, and even that appnote distributed to OmniVision FAEs only!

It contains sequences of registers to convert from one mode to another.

[CharlesDias]

damn it could have been so easy :D

If it were easy, it wouldn't be fun and rewarding! Congrats, @CodingGhost !

About JPEG, I didn't have the opportunity to dig into. By the way, the DCMI driver does not support JPEG so far. ASAP I'll start to work on this improvement.