STM32 LTDC TFT-LCD controller and low power modes

[vesusejage]

Posted on October 05, 2016 at 00:53

Hello, I have trouble understanding something about the LTDC, bare LCDs and STM32 low power modes. If the TFT-LCD controller sends an image to a bare LCD (no controller, no framebuffer) and the STM32 then goes in STOP mode for a minute, will the image keep being displayed on the LCD ? Thank you, Jage

[Tesla DeLorean]

Posted on October 05, 2016 at 01:43

I'm thinking no. The clocks and pin drivers are likely to be pulling the bulk of the current in any case.

[vesusejage]

Posted on October 05, 2016 at 01:55

I would think no too but ''2.2.3 Running application steps'' (page 19) in ''Managing low-power consumption on STM32F7 Series

microcontrollers'' [1] has me doubting. In this low power example, an image is sent and the MCU goes in STOP mode but they don't say if the image is retained.1: www.st.com/resource/en/application_note/dm00219305.pdf

[Walid FTITI_O]

Posted on October 05, 2016 at 12:12

Hi 

vesuse.jage, 

The image Display is achieved during Sleep mode which is after Run-3 ( as indicated in 

Figure 6. Application low-power transition states). Then the RTC wake-up the CPU to enter then to STOP mode. In the STOP mode, all the peripheral clocks are gated, so the display is stopped. The device remains in stop mode until RTC time elapsed or a wake-up bottom is pressed before that. Hope it is clear for You now.-Hannibal-

[vesusejage]

Posted on October 05, 2016 at 21:55

Thank you for your answers. I will then use an LCD with a controller+framebuffer chip.

I would like to use an external SDRAM connected to the FMC too. Now, to transfer from this SDRAM and the LCD, are there any advantages to the LTDC or is FMC good enough ?We would like HS-USB too and :       HS-USB+SDRAM+LCD over FMC is possible on LQFP144,       HS-USB+SDRAM+LCD over LTDC would require LQFP176.Thank you !

[Walid FTITI_O]

Posted on October 07, 2016 at 19:44

Hi vesuse.jage, 

Yes the FMC do the job.-Hannibal-