Choice STM32 model with supporting high screen resolution - Page 1
Forum section: electronics / beginners

author: stntter
author_rank: Newbie
timestamp: April 03, 2022, 08:45:00 am
content: Hello! I want to do my petproject with stm32 and display.Ran into a problem with a choice of model supporting large resolution (5' 720*3RGB(H)X1280(V) for example).I tried filter in STM32Finder with TFT LCD (394 items found), but i need to look at each model for details. Example in attach.May be I do something wrong and is there an option to choose a cheap stm32 and some separate video module for such a resolution?Tell me, please, how to do it right?

author: TassiloH
author_rank: Regular Contributor
timestamp: April 03, 2022, 12:23:58 pm
content: I don't think any of the STM32F4 / F7 microcontrollers support the resolution you want - their TFT peripheral is limited to XGA (1024*768). The "total width" etc. from your example refers to the total scan line width including back porch and sync. The reference manual for the STM32F4 series is more specific and says the "active width/height" is limited to 0x400/0x300.I believe even the STM32H7 series uses the same peripheral, but I am not sure.Another thing to consider is the required memory and memory bandwidth - for bigger displays external SD-RAM is required. I have an application with a 800x480 display and 16bpp/60Hz using external 16 bits wide SD-RAM on an STM32F429. This requires about 50MBytes/sec and works fine, but e.g. the dual-layer feature of the TFT-controller is almost useless. Any significantly sized second display layer uses so much bandwidth that there is barely enough time left for write accesses (as long as you want to update significant portions of the image frequently), leading to display errors during writes of larger data amounts. So I guess even to use the XGA resolution in true color (24bpp) and 60Hz one needs 32bits wide SD-RAM and is somewhere at the memory bandwidth limit, no point in supporting bigger displays.For your requirements you probably have to look into an external display controller, but I have no clue what is on the market there.

author: DavidAlfa
author_rank: Super Contributor
timestamp: April 03, 2022, 09:39:15 pm
content: Anything over 320x240x16bpp will require SDRAM, that small resolution will already eat 150KB, quite a lot from the typical 192/256KB SRAM these MCUs have!Better you ask inhttps://community.st.com/!

author: SiliconWizard
author_rank: Super Contributor
timestamp: April 03, 2022, 09:47:26 pm
content: The STM32U5 series, which is pretty low power, has 786KB of RAM.Otherwise, you have the STM32H7 series, with up to 1MB (or a tad more, even), much more powerful, much more power hungry as well.

author: DavidAlfa
author_rank: Super Contributor
timestamp: April 03, 2022, 10:00:44 pm
content: Yep, but also limited to 1024x768. STM32MP are beast... but BGA-only!

author: stntter
author_rank: Newbie
timestamp: April 04, 2022, 07:48:15 am
content: TassiloH, I foundhttps://aliexpress.ru/item/1005002089493595.htmlthis. I'm correctly understood, that I can to interact with this UART and all UI will be managed with external processor t5l asic (https://forum.duet3d.com/assets/uploads/files/1611933767118-development-guide-of-t5l-asic_20200624.pdf)?If this true, i can use cheap stm32)

author: TassiloH
author_rank: Regular Contributor
timestamp: April 04, 2022, 08:12:36 am
content: Yeah, this display will manage the complex part of the UI. You store graphics, fonts etc. either on the internal flash of the display or on an SD-card and then just invoke your pre-defined UI pages via the serial port. Just keep in mind that this is a good approach for most applications except if you generate a lot of data on your microcontroller that you want to visualize (like color maps etc.) and the speed of the serial link would be limiting.

author: Berni
author_rank: Super Contributor
timestamp: April 04, 2022, 09:56:26 am
content: STM32 in general will have issues with anything above VGA resolution because there SDRAM interface becomes too slow to handle the bandwidth.But there is the STM32MP1 series that has a DDR2/DDR3 memory controller inside it. It should handle even HD resolutions just fine, but it is a chip capable of running Linux so writing baremetal C code for it might be quite a bit more complex as compared to a regular STM32F4 MCU. Tho you might actually want to run Linux on it anyway because this gives you OpenGL access to the built in GPU, so that you can push a lot more pixels around (As opposed to pure CPU drawn graphics).As for these "inteligent LCDs" they can be a good fit for mostly static UI where you have a bunch of buttons around and some settings. If you need anythyng more advanced like say drawing graphs or heatmaps etc they won't work because even the interface is too slow.

author: stntter
author_rank: Newbie
timestamp: April 05, 2022, 12:50:15 pm
content: Thank you, Berni!I need to calculate what will come out cheaper, find an STM32MP1 somewhere and find a suitable display or take a display with an external driver) of course, the STM32MP1 option looks really good.I was going to order on jlcpcb, but they are out of stock (