Guidance regarding using LTDC Controller in STM32L4R5ZI based Nucleo Board.

@Martin KJELDSEN​ any thoughts? We wanted try this out on a Nucleo board NUCLEO-L4R5ZI. and we want to be able to use the LTDC controller to drive the LCD, however since we want to be able to use the ZIO connectors for the GPIO PINS to connect to the external LCD display, are there any restrictions on only using pins that are classified to have an alternate functions of LCD_HSYNC, LCD_VSYNC etc.?

Thanks,

Yogesh

Only the pins classified to have an alternate function for LTDC.

You can refer to this AN for more details:

https://www.st.com/resource/en/application_note/dm00287603-lcdtft-display-controller-ltdc-on-stm32-mcus-stmicroelectronics.pdf

Thanks AME Support and Martin for taking the time to respond and for the clarification. So in short when I look at the reference manual or the user manual for the L5 Module we plan to use, any of the pins that have the LCD_* alternate function assigned against them, when I load up this nucleo development board in CubeMX, all I have to do is choose those specific pins and choose the alternate function, so that LTDC peripheral can use those pins? Do I have do this explicitly or I don't have to even do that since the LTDC will use those pins as soon as I enable it? I am asking these questions, because eventually we will create a custom board of our own and we will have to tie these pins to the display panel and also I need the clarification because the concept of alternate functions has been a subject of confusion for me :).

@Martin KJELDSEN​  you mentioned that "TouchGFX L5 support goes, it's on the list of things to do", by that did you mean currently a TouchGFX example doesn't exist for the L5 board and that would be made available soon?

Thanks,

Yogesh

Thanks @Community member​  for taking the time to respond. I didn't realize I have been typing L5 :). I have gone thru' most of that document related to LTDC topics and the alternate function pins. Also we know the display we plan to use has a 24 bit bpp. so we will be using all the 24 RGB pins and more to control other things like clock, control and sync related pins. However all I was trying to get a clarification is whether I need to explicitly configure those pins in cubemx that have an alternate function of LCD_* defined or by just enabling the LTDC peripheral in cubemx, these pins automatically are used, without me having to choose and configure those pins?

Thanks,

Yogesh

Hello,

If you use CubeMx and enable LTDC it'll use the default LTDC alternate functions.

Then it is up to you to remap the LTDC pins to other possibilities. You need to refer to Table 17. Alternate function in the datasheet.

For example, CubeMx will use by default PE2 for LCD_R0. Then you can manually change it to use PG13 for LCD_R0.

LCD_CLK, LCD_HSYNC, and LCD_VSYNC have one single option: PD3, PE0, and PE1 respectively.

This is per the datasheet:

https://www.st.com/resource/en/datasheet/dm00366448.pdf

Hope it is clear for you now!

Thanks that helps a lot and clarifies my questions.

Thanks,

Yogesh

By the way, STM32L4R5ZI devices don't have the LTDC peripheral (LCD_TFT) - Refer to Table 2

https://www.st.com/resource/en/datasheet/stm32l4r5zi.pdf

I am confused, in the features it says the STM32L4R5ZI following regarding the Graphics related features. Does the presence of an LCD-TFT controller not mean it supports LTDC? Also if we want to use these board to eventually drive a 24 bit display, how could we use the LCD-TFT controller to achieve the same as the LTDC?

Advanced graphics features

• Chrom-ART Accelerator (DMA2D) for enhanced graphic content creation
• Chrom-GRC (GFXMMU) allowing up to 20% of graphic resources optimization
• MIPI® DSI Host controller with two DSI lanes running at up to 500 Mbits/s each
• LCD-TFT controller

Thanks,

Yogesh

It is extremely misleading that on the stm32L4R5ZI product page under key features its list out as shown below. It should be clearly called out on the product page the only thing it supports under graphics feature is chrom-art accelerator and not the other three listed out.

https://www.st.com/en/microcontrollers-microprocessors/stm32l4r5zi.html

Advanced graphics features

• Chrom-ART Accelerator (DMA2D) for enhanced graphic content creation
• Chrom-GRC (GFXMMU) allowing up to 20% of graphic resources optimization
• MIPI® DSI Host controller with two DSI lanes running at up to 500 Mbits/s each
• LCD-TFT controller

Thanks,

Yogesh