7" inch tft display project - Page 1
Forum section: electronics / beginners

author: christos
author_rank: Regular Contributor
timestamp: August 14, 2021, 12:59:09 pm
content: Hello!Not really a project but a question to find a way to make a 7" tft display to work with a microcontroller.I have a AT070TN90 tft with 50 pins and would like to know how to control it with a stm32.The main problem is that I dont have a clue on how it could work. Is there any way to control these 50 pins via a display driver or any other chip?I made a block diagram on paint of what I think is the correct way to control the display.Thank you!

author: darkspr1te
author_rank: Frequent Contributor
timestamp: August 20, 2021, 06:59:04 am
content: You will need to provide a bit more on the project, which stm32 you wish to use (eg stm32f407 has dsi for connecting to lcd's)the AT070TN90 models have different interfaces depending on brand/modeltry this place for datasheets.https://www.displayfuture.com/engineering/datasheets.aspalso what language /compiler setup are you wanting to use ? there is stmcube mx , arduino, libcm3some support glcd some support lvgl graphics/lcd libsdarkspr1te

author: amyk
author_rank: Super Contributor
timestamp: August 21, 2021, 06:23:50 am
content: Take a look at these:https://www.st.com/resource/en/application_note/cd00278141-qvga-tftlcd-direct-drive-using-the-stm32f10xx-fsmc-peripheral-stmicroelectronics.pdfhttps://www.st.com/resource/en/application_note/dm00287603-lcdtft-display-controller-ltdc-on-stm32-mcus-stmicroelectronics.pdf

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 21, 2021, 08:19:09 am
content: Do you have any expectations in mind, as to what to expect from your interfaces?I2C is utterly helpless here; sometimes it appears on panels for configuring settings, or touch controller, stuff like that. It has far too little bandwidth to transfer video. (I'm not sure what displays are even available for video over I2C; probably just small character displays or the like?)SPI is marginal at best. At a typical 10MHz maximum, it's just passable for small e.g. 160x128x16bpp displays, capable of a full refresh at maybe 20 FPS. A bigger panel might support up to 50MHz, but even with quad channel (QSPI) it's going to be a stretch.Most controllers, for panels of this size, have a parallel interface I think; the speed is similar but transferring whole bytes/words at a time is obviously a win. Full speed, full screen video (60FPS) is feasible I think.Not that it's a prerequisite that the controller and CPU be capable of delivering live video; PCs didn't even have that until the 90s (special hardware aside). But it's a good wave-of-the-hand baseline to get a feel for how much power you might want to pair with the thing.Your panel is digital RGB, which requires an external controller (framebuffer, addressing, sync generation, etc.). Some micros have this internal, e.g. STM32F417 I think. Note that sharing video and system RAM (you likely need to add an external SDRAM) will have some performance impact on the CPU; don't expect the world out of it. (Probably still enough to run Doom, for point of reference.If maybe not at full screen.)You can get standalone controllers for these. I've played with one before, though the board I made doesn't quite match your panel's pinout, so you'd have to make an adapter cable to use it; but I do have spares if you're interested, and are able to solder SMTs (it's about 50 components, the most difficult being a 0.4mm pitch TQFP, or a no-lead; hot air or oven reflow is required). It uses an Epson S1D13517F00A100, a... fairly pricey (and, apparently out of stock right now..) controller, which presents a parallel 8/16 bit interface. Would be a good match to an STM32 parallel port, or even FSMC.https://imgur.com/gallery/w1FjqoXThis is writing a test pattern, then an image from SD card, using an 8-bit MCU (XMEGA).As for available options, I don't know, I haven't shopped display controllers very much -- YMMV.Since this panel is available from Adafruit, have you checked what resources they offer? More pointedly, have you checked what it is (the panel, datasheet), what's recommended for it, etc. at all..?Tim

author: mon2
author_rank: Frequent Contributor
timestamp: August 22, 2021, 03:53:53 pm
content: Agree with the comments here and adding...1) for this rather large display, you will want to work with a MIPI DSI interface.2) respectively, you will want to select a micro that offers the MIPI DSI interface or as a plan B, use a parallel to MIPI bridge (ie. Solomon) but this approach will require some custom coding which for now is not recommended.3) for the sake of sanity, download and dry run the ST TouchGFX toolchain (free) and select a supported kit from their GUI tool that features the DSI interface. Once you are ok with the selection, proceed to purchase this kit (they are not that costly vs. the amount of time you will save as their wizard will do the heavy work on your behalf). Before you jump in, do check on the availability of the STM32 CPU onboard the kit if you plan to build your own widget. STM32 devices are not easy to find in this crazy state of the world today.4) a totally different approach is to purchase a rather low cost Raspberry PI with an HDMI interface and then proceed to use one of the many HDMI to MIPI kits on Aliexpress that can easily drive this size display. Plenty of support for the RPI devices.