Esp32, TFT SPI speed

[gcrcien]

Hello everyone,

I’ve been working on an ESP32-based SDR for a while now and the receiver is working well. For the next hardware revision, my main goal is to improve the UI refresh rate (waterfall/spectrum), since the current display feels sluggish.
Current setup
MCU: ESP32-WROOM
Display: 4" ILI9488 TFT
Interface: SPI
Library: TFT_eSPI

The display seems to be limited to around ~28 MHz SPI. The listing claimed it was an ST7796, but it turned out to be ILI9488, so performance is not what I expected.
As a reference: I previously used an ILI9341 display and was able to run SPI at around ~80 MHz, which felt much smoother.

Are there any 4" (or bigger) TFT displays that are significantly faster than the ILI9488 over SPI when used with an ESP32?
Or any supplier that sells real st7796 TFT modules that you know of?

Using 8/16-bit parallel instead of SPI if that’s the realistic path but I’d like to keep pin usage low for now

[langwadt]

afaik none of those controllers are rated for more than 30MHz spi, though some might work

it might not be the controller, those boards usually have a 5V to 3.3V translation, that might be slow

[gcrcien]

WELL DAMN 

Is there any other tft module that supports these faster speeds? it would be a wonderful upgrade to this project

[Rudolph Riedel]

Interesting, I just had a discussion about a waterfall display for a spetrum analyzer last month: https://github.com/RudolphRiedel/FT800-FT813/discussions/162

We are using Bridgtek display controller, these work fundamentally different in that these take a display list over SPI instead of raw pixels for most operations.

The solution I did for the waterfall display still generates a single pixel line bitmap for every waveform and writes that to the graphics controller.
And with each update a new line is written to a different memory location.

But then the display itself shows the current line at the top as one image, and the rest of the lines as one or two images, depending on the position of the current line in the memory which is actually used like a ring-buffer.

So the lines are not copied around and only written once, the display controller is just told to animate the waterfall.
This works as the memory is used continously and for the controller it makes no difference if the bitmap has 1 line or xx lines.

With a 750 x 450 waterfall and the waveform on top of that my display update took 387µs on a STM32F407 and 10MHz SPI, plus 3.3ms transferring the data with DMA.
Targetting 50 updates per second that leaves quite some time for data aquisition and calculations.

Sure, a RVT50HQBNWC00 for example from Riverdi costs a lot more, but I really having fun with EVE based displays.

Oh yes, my library does support ESP32 as well, with DMA.

[gcrcien]

Interesting, im going to give it a deep read, letting the screen controller animate would relax the load on the ESP32 giving it more room to do DSP and other functions, thank you very much.
I was considering EVE for my board but now i think its time to actually work on it .