DCMI format support

[armindavatgaran]

Posted on July 02, 2015 at 14:10

Hello

According to DCMI section of stm32f407 datasheet and RM0090, RGB565 is supported.

Is raw RGB(888) supported too?

Thanks.

[nesrine]

Posted on July 02, 2015 at 14:51

Hello,

Checking RM0090 reference manual:

In the paragraph 15.6.3 RGB format: it said that “Only 16 BPP (bits per pixel): RGB565 (2 pixels per 32-bit word) is supported. The 24 BPP (palletized format) and grayscale formats are not supported»: so the RGB888 is not supported 

I hope this answered your questions.

Syrine

[Tesla DeLorean]

Posted on July 02, 2015 at 17:23

I'm not sure the DCMI really cares what format the data's in, it provides a 8-14 bit wide parallel interface, and timing signals.

The limits would seem to be driven by speed, bus width, and DMA frame size.

[armindavatgaran]

Posted on July 03, 2015 at 14:47

According to what clive1 said, how can dcmi distinguish between different formats, whether it is raw RGB or RGB565 ?

[Tesla DeLorean]

Posted on July 03, 2015 at 16:25

The format of data received in memory is going to be primarily dependent on the format your source device has been configured to send it in, the bit/byte ordering, the colour depth, and format. And then how the STM32 buffers, writes, or aligns, into it's 8, 16 or 32-bit memory space.

I haven't had cause to do much with the DCMI, but my understanding is it's just copying data into memory via DMA, either a byte at a time, or 14-bit words as 16-bit half-words on the ARM side. I'm sure a picture is painted in the manual, and you can look at, or analyze, the data in your buffers.

It's the display side device that's going to be most dependent on the RGB formatting, and if you expect to be able to pipe the camera directly to the display, the formats are going to need to be coherent. In most cases, you might have to transcode image data between differing formats.