STM32 LTDC vs 8080 interface (for low-power applications)

[Tuoman]

Hi,

For LCD interfacing, is there any reason to use 8080 over LTDC, than to save GPIO pins?

Previously I have understood 8080 is better in power consumption than RGB, because the display is not constantly needed to refreshed. But how does LTDC fix this? It uses RGB also, so does it actually get lower power consumption than 8080 interface?

https://www.st.com/content/ccc/resource/technical/document/application_note/group0/25/ca/f9/b4/ae/fc/4e/1e/DM00287603/files/DM00287603.pdf/jcr:content/translations/en.DM00287603.pdf

"FTDC: Ideal for low power and mobile applications such as smartwatches."

Thanks.

[Tesla DeLorean]

The LTDC can feed to DSI, and that uses less pins than either.

Low power would be an end-to-end issue. You can move the consumption to the display if it has its own controller/buffer, rather than you holding the memory and driving the signals. Large displays have a lot of memory behind them with significant clocking/bandwidth that comes with that.

What sort of graphics/display does you application need? Does the display need to persist in the low power mode? Do you have animation/interactivity?

Would ePaper display be viable?

[Tuoman]

Thanks for reply.

>What sort of graphics/display does you application need? Does the display need to persist in the low power mode? Do you have animation/interactivity?

Would ePaper display be viable?

It is 320x240 display, simple animations, such as transitions might be necessary. Display is on active when used, just like mobile phone. It shows changing measurement data, graphs and numbers, as well as menus. E-paper is too slow.

>The LTDC can feed to DSI, and that uses less pins than either.

Use of pins is not an issue. I prefer low-power technology, that is fast enough for animations. I can even use RGB interface if necessary. I assume serial will be two slow for animations.

So far I thought 8080 is the best in my use, but this LTDC solution was new to me.

>You can move the consumption to the display if it has its own controller/buffer, rather than you holding the memory and driving the signals. Large displays have a lot of memory behind them with significant clocking/bandwidth that comes with that.

I thought that RGB driving requires more energy, than LCD with integrated controller right? With RGB, MCU needs to be processing always. 8080 is only updated when necessary, not all the time. But is this consumption negligible compared to backlight? And is it irrelevant if measurement values or menus on screen keep changing, and I need to keep the MCU active when the display is used anyway...

Are RGB, 8080 and Serial all viable options in this use-case?