STM32L4 and DCMI with 24bpp

[AJans.3]

Hi,

I´ve done a lot of reading and testing...

For some reason, its stated in both the datasheet and the DCMI application note that 24 bit per pixel formats are not supported.

Trying to understand why...

The DCMI is "stupid" in the sense that we only tell it how many bytes to read.

It doesn´t know anyting about the format and just shuffles data through DMA into the buffer.

I´ve done a lot of testing with the eval board and the OV5640 camera but for some reason get the wrong colors (or something mismatches). Even though with making sure that the pixels number align with correct number of 32-bit words.

I was just hoping that someone has an explain why it doesn´t work...

[Tesla DeLorean]

>>.. that 24 bit per pixel formats are not supported. Trying to understand why...

Most likely because groups of 3 bytes are handled by the DMA or other HW efficiently.

In other 24-bit imaging each pixel has it's own word, with a slack byte.

The 14-bit forms go into 16-bit words, supported by the DMA

I'd imagine that 8-bit forms, be it JPEG bytes, 8-bit color, or 3-byte RGB triplets, would in fact be captured, and provided everything was suitably clocked and synchronized, that you could pick through the capture buffer. Not going to be efficient, and high frame rate.

I've not spent much time on the STM32 video capture side of things, as the resolution is woeful, and the resources of the system are pretty limited/arcane. We're talking about people who designed DMA units with 16-bit transfer counts..