Could any STMCU be used to drive dual LCD screens?

[srony]

Hello Guys,

I am searching for a MCU to drive dual LCD screens. Although I see some MCU (eg, STM32U5G9ZJTXQ) providing both DSI and RGB mode interfaces without pinout collision, I didn't see any description about whether the LTDC can output 2 different images to the different interfaces respectively. Can I get your experiences sharing?

Thanks in advance,

SRONY

[AScha.3 · Accepted solution]

Hi,

if you use TFT's with a standard SPI interface , (for example) no problem to connect 2 or 3 displays , if enough SPI's on the cpu .

I use TFT with EVE controller ...like this :

https://www.matrixorbital.com/eve3-70a

https://www.mouser.de/c/optoelectronics/displays/lcd-displays/tft-displays-accessories/?series=EVE3

Displays have the EVE graphics controller onboard, so no memory problem on the cpu . 🙂

[srony]

Ohh, yes, I see. An additional display driver is required for dual displays. Seem indeed no ST MCU was designed for dual-display driver.

[AScha.3]

Right...but with TFT (with EVE = onboard graphics controller + ram ) you just need a "setup" group of commands, to make a new full screen on the next frame , instantly. 🙂

The display controller also can give an INT, when (e.g.) a menu button is touched, or x-y coordinates on any touch etc.

[Tesla DeLorean]

Video memory and bandwidth are limiting factors. Limits the resolution.

There's only one LTDC, and you can't multiplex that.

You could perhaps make a screen wider and shorter, so you could get two "frames" in view, But I'm not sure you can get much beyond 1.2 Mpixel

[srony]

Just now I looked through the LTDC chapter and DSI Host chapter in Reference manual. The DSI Host just is an interface converter, it converts LTDC RGB interface to DSI interface. And the LTDC can output video frame to external RGB interface and DSI Host LTDC interface. So the external DSI interface just is the mirror of external RGB interface.

[Tesla DeLorean]

>>So the external DSI interface just is the mirror of external RGB interface.

Well its just a funnel, one goes into the other, the DSI need to off-load at least as fast as the LTDC is shovelling data to it.

STM32 DSI implementations are limited to two lanes, so about 1.25 Mpixel at 50 Hz 16 bpp