Does the STM32F have separate video memory?

[HElia.1]

I am currently looking for a microcontroller or processor with MIPI DSI output. The STM32 devices have this, but there is something that does not seem to make sense. They only have 512kB of internal memory. This would not be enough to hold a single frame of video to output to the screen.

The screen on the Discovery kit is 800x480 pixels x 24bits/pixel. This equates to a little more than 1MB of data.

Do these devices have additional video memory, enough to hold a video frame ready to be streamed out to the screen via MIPI.

Or do these devices require additional external RAM to be able to drive a display of this size?

[Peter BENSCH]

Welcome, @HElia.1​, to the community!

STM32s are not processors, but microcontrollers that are intended to contain as many functions + memory etc. as possible in one component. Depending on the requirements, the processing of video can be very computationally intensive, which is why microcontrollers are usually overburdened with this.

Depending on the requirements, you have to make compromises: either work with external memory as a frame buffer, or reduce the colour depth, for example - or both. 

With small and simple displays, there is usually no noticeable difference between graphics in RGB888 (24bit/pixel) and RGB565 (16bit/pixel), but the memory saving is enormous.

By the way, the STM32 with MIPI-DSI is not only available with 512KB RAM, but already with 1MB and soon also with 2.5MB.

Does it answer your question?

Regards

/Peter

[HElia.1]

Thanks Peter,

Just asking about the memory. Very interesting to hear that there are 2.5MB version available soon. That's easily enough internal memory for my application.

Hugo

[Tesla DeLorean]

Small low resolution screens need less memory.

Higher resolution screens use external SDRAM.

Significantly higher​ resolution screens run out of memory bandwidth and DSI lanes.

So nothing much beyond above 1280x1024, and definitely not FHD or UHD, and no video decompression ​

[HElia.1]

Thanks Tesla DeLorean,

This answers my question. There is no separate video memory, and so larger screens will need to use external memory. No problem.

Many thanks

Hugo