FAQs
cancel
Turn on suggestions
Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.
Showing results for 
Search instead for 
Did you mean: 

Why the WXGA (1366x768) at 60fps limitation for STM32MP157C MPUs?

Go to solution
AlexeyR
Associate II

‎2019-09-24 10:31 AM

I am evaluating different dual-core ARM Cortex-A7 MPUs for their graphical features; one of my requirements is that I need to support a 1280x1024 TFT LCD at 50-60fps using 16 or 24-bit parallel RGB interface.

The evaluation kits offer small LCDs below my requirements, and I need to make sure that the MPUs can support what I need.

Looking at the datasheet for STM32MP157C MPUs, it is clearly stated in multiple places that the upper pixel resolution limit for the LTDC module is WXGA (1366x768) at 60fps. However:

  • the max pixel clock - LCD_CLK is stated to be 90MHz at specified supply voltage range. At that clock frequency, barring any external memory-related bottlenecks and assuming some small HSYNC/VSYNC + porch timings, I should be able to run a 1280x1024 LCD at around 63 fps max - and for sure at 60fps. Involved memory transfer clocks seem to be fine as well (I could be wrong on this one).
  • LTDC register definitions seem to support much larger width and height values than what I need, so I should be able to program it to do what I need it to do without a problem.
  • One of the product training presentations from ST states that "Higher resolutions are possible" using LTDC, but at lower FPS. Again, the stated clock limit should allow for much better performance

With these assumptions, what ends up being the bottleneck here? Why the oddly-specific WXGA specification in the datasheet?

Thanks!

Labels:
0 Kudos
11 REPLIES 11
Go to solution
CodeWander
Associate II
In response to PatrickF

‎2019-12-13 07:29 AM

Hi PatrickF, Sorry for the intrusion. I asked this in a separate thread (with now reply, so far :downcast_face_with_sweat: ), How to enable a third party 3.5" NewHaven Display (320x240!!) connected to the LTDC port on STM32MP157C-EV1 board? Do I need to modify some config file to load the LTDC driver, or the device tree files (and rebuild linux...)? I want to display the default apps that come with the STM32MP157C-EV1 on this second 3.5" display. How do I enable the LTCD display driver? Do I physically remove the original 5.5" display form the DSI port?

I also built the OpenCV for ARM7 and used it to capture a Boson thermal imaging camera connected to the USB port on the EV1 board. It works with the 5.5" DSI display (in parallel with the default camera that comes with the board, or my own Logitech USB web cam). I want to display all of this on the 3.5" display mentioned above. Thank you for your help.

(If you don't help me I am going to get fired! NO, JUST KIDDING, but I do not feel all that smart right now! :face_screaming_in_fear: ).

The 3.5" display, NHD-3.5-320240MF-ASXN#, has a Built-in Driver / No Controller and is a 24 bit Interface.

0 Kudos
Top