What is the highest resolution LCD that can be cleanly directly driven by an STM32 these days and developed with TouchGFX? - 800x600? 1024x768 HDTV more/less? - How many bits Colour? - Which STM32? Paul

[Peter BENSCH]

Hi Paul,

the LTDC of the STM32F4, STM32F7 and STM32H7 supports up to XGA (1024x768) with 24bit in RGB888, while the GFXMMU of the STM32L4+ supports up to 1024x1024 (32bpp) or 2048x1024 (16bpp).

Regards

/Peter

[Paul1]

Hi Peter,

The STM32L4+ chips STM32L4R9 (MIPI DSI) and STM32L4R7 (TFT) look good.

a) I really like the DSI since less wires and can drive a fair distance, but it appears to be uncommon?

Can the MIPI DSI drive the DSI input on a standard computer monitor? (I couldn't find many LCDs with MIPI DSI input, so I'm leery of using it).

We are using 7" to 12" displays at this time.

b) Do you know where I could find demo modules, examples, or app notes for the STM32L4R9 or STM32L4R7 that have higher resolutions displays? (maybe 1024x600 or higher). I looked through the ST website, but wasn't able to find anything for these that had larger LCDs, just the STM32L4R9 demo with the small round display.

Thank you

Paul

[Tesla DeLorean]

Just needs a chip to get into HDMI/DVI connectors. With two lanes you run out of bandwidth as the pixel count explodes.

Published numbers for a working 1024x600 on other threads

Was able to drive monitors at

1024x768 at 50 and 60 Hz

1280x720 at 30 Hz

1388x768 at 25 Hz

800x600 at 60 Hz

768x576 at 60 Hz

640x480 at 75 Hz

Was using a F769I-DISCO and B-LCDAD-HDMI1

7" 800x480 is the largest panel I've seen on an ST dev board.

[Paul1]

We were avoiding HDMI as the product would need licensing from HDMI, and that is totally unreasonable cost at our low quantities - unless the chip you mention includes the HDMI license?

1024x768 looks good for us.

Paul

[Tesla DeLorean]

Sure, but then you have to own the interface / connectorization.

I'd expect you'd have to own the HDMI licencing if you use that, chip vendors don't carry your portion of it.

There should be panels that take DSI, the larger ones will tend to assume you have 4 lanes, but that's often configurable, just got watch the 1Gbps ceiling (ie 2x 250MHz DDR, 500Mbps/lane) with your pixel clock, and colour depth. And your ability to factor all the PLLs within the limitations of the hw/settings there, pixel clock, line totals and the transit points for the data.

The take-up rate on the DSI >= LTDC delivery rate.

Seem to recall TI, or someone, having DSI to Parallel RGB chips.

Probably DSI to VGA out there too, but haven't looked.

Perhaps start by looking at panels you like from a price/quality/availability stand-point, and what that tells you about the direction to focus on.

[wired]

Been having the same issue with MIPI-DSI being a rare bird. I'm looking to use something very similar to the display on the STM32F469i-DISCO (4" 480x800 IPS TFT w/CTP). That panel can be purchased through Alibaba in large quantities, and there are a few others I've found that are similar, but that's about it. I also can't find any information out there about which display controllers are obsolete and which ones aren't. The DISCO uses an OTM8009A controller, which is fairly old.

[Paul1]

I've been checking with Raystar as I'm actually looking for 7" to 12" displays

I'm wasn't concerned with the ICs on the LCD as long as both the STM32 and the Display support the same MipiDSI spec. Now of course I'm wondering, and of course samples and testing were always required.

If anyone has experience with MipiDSI Displays connected to any STM32 please share what worked, and what didn't. It could save us a lot of agony.

If anyone knows of other STM32 + MipiDSI demos please share info.

At this point I'm considering STM32L4R9=MipiDSI (STM32L4+)

and also STM32H747(757)=MipiDSI

I have a lot of investigation to do, including [display memory/RAM/buffers].

Paul

[Tesla DeLorean]

The market for these types of things is very flighty, by which I mean they are working in spaces with 12-18 month product cycles, build a shed load, and then move to the next thing. It is driven by large orders for specific phones, tablets, etc, and then is gone. These aren't people sitting around thinking about others using it for 2, 5 or 10 years. The availability of parts tends to relate to how many were initially produced, and inventoried somewhere. And old parts might be designed in quickly if the availability/pricing are good for a production run.

You'd have to query the controller vendor, for a quote or roadmap, or check inventories held by parts brokers.

[wired]

Well, if you're considering the STM32H747, their DISCO board uses the same MIPI-DSI display that I'm using on the 469i DISCO board. At least you'd have a working starting point.