> That is only partially correct ... Interesting would be the next command

The next command reads the chip ID from REG_ID register (0x302000): if the content is not 0x7C the whole wakeup sequence (reset, set CLK...) is repeated.

So I assume the chip runs at 60 MHz.

The next command after CLKEXT should be ACTIVE if it is not CLKSEL.
But yes, correct, then this is followed by reading from 0x302000 and it looks like you have the BT817 running at 60MHz.

So one thing to optimize could be to run the BT817 at 72MHz which also increases the clock for the external SPI flash.

>> I am not able to tell what the frame rate is

> It either is 61.58Hz with 60MHz clock or 73.89MHz with 72MHz clock.

Uhm... how do you calculate that? I thought that I should take the PCLK and divide it first for display width and then for display height (grossly). I obtain a frame rate of about 78 Hz (which is 30MHz divided by 800 then by 480), so I thought I could lower it down to 30 FPS to give more time to the GPU.

Is my reasoning correct? I mean - I should lower the framerate in order to ease the GPU job?

Almost, the framerate is pixel-clock / (VCYCLE * HCYCLE).
And lowering the framerate might help, for example by setting PCLK to 4.
As you have a BT817 you also can configure the pixel-clock a bit more directly by using the second PLL.
Also, within limits, the config can be tweaked to use more clocks per line.

But I would rather put as much as possible in RAM_G before displaying directly from FLASH.
The pixel engine really has to do a lot and random access to a serially attached external memory does not help.

The main clock is external, set by writing 0x44000000 during initialization.

That is only partially correct, the host commands are three bytes long and CLKEXT is 0x44 0x00 0x00.
Interesting would be the next command, if it is ACTIVE then the BT817 runs at 60MHz.
If it is CLKSEL followed by 0x46 then the BT817 runs at 72MHz - 0x61 0x46 0x00.

I am not able to tell what the frame rate is, using the above parameters - I just copied them from an example and they work.

It either is 61.58Hz with 60MHz clock or 73.89MHz with 72MHz clock.

What library is this exactly and in what version?
What TFT are you using?

BT816Q with an ESP32-WROOM-32E connected over VSPI at a 26 MHz clock.

Ok, I did some maintenance on  my library yesterday, so I dug out an ESP32-WROOM32 board for it
and connected to a an EVE3-50G which has a BT815.

We're using a modified version of your library and the ESP-IDF.

Modified how, anything that I should consider as well?

This morning I started a test using the PlatformIO project for ESP32 using ESP-IDF.

I modified the SPI clock in EVE_target.c for the display-update transfers with DMA to:
devcfg.clock_speed_hz = 26U * 1000U * 1000U;

I left the the SPI clock for single transfers at 10MHz as this is used to initially configure the EVE chip and
I observed that reading starts to fail at lower clock speeds than writing.

The display-refresh is at 50Hz.

In TFT_display() I added this:
static uint16_t fault_counter = 0;
static uint16_t reg_dlswap_faults = 0;
...
if(EVE_FAULT_RECOVERED == EVE_get_and_reset_fault_state())
{
  fault_counter++;
}

if(0 != EVE_memRead8(REG_DLSWAP))
{
  reg_dlswap_faults++;
  return;
}
...
EVE_color_rgb_burst(BLACK);

EVE_cmd_fillwidth(130);
EVE_cmd_text(10, 150, 28, 0, "First line\nSecond line\nThird line\nFourth line\nyet another line\nand one for good measure");

uint32_t arguments[2];
arguments[0] = (uint32_t) fault_counter;
arguments[1] = (uint32_t) reg_dlswap_faults;
EVE_cmd_text_var(10, 100, 28, EVE_OPT_FORMAT, "Faults: %d %d", 2, arguments);

We have 16:50 now and this is running since 9:45.
It still displays "Faults: 0 0".

So at least a longer line of text with a couple of line-breaks does not show an issue.

I do need to invest in a good logic analyzer as it's too difficult to pick out the data using our scope even though it does have a decode function; doesn't help that we also have two CAN controllers on the same SPI bus as the display so there's a fair bit of traffic going around.

I very much prefer Saleae: https://www.saleae.com/de/
But then I did not pay for neither the Logic 16 I currently have burried somewhere in the pile of boards and displays on my desk,
or the Logic Pro 8 I have in my lab at work.
The Logic 16 is a couple of years old and won't do in this case, it "only" works with 50MS/s when measuring 4 or 5 channels.
The sample rate should be several times higher than the clock of the signal to actually see details in the timing.
So with 26MHz SPI clock I would not use less than 200MS/s - and more is better.

And the Saleae Logic software decodes SPI.
Which reminds me that I started to write a high-level decoder for the EVE chips,
but it turned out to be not as straighforward as I hoped it would be.


As you can see in the attached image, I am using an ESP32 board that looks like an Arduino UNO.
The jumper wires to my adapter board are about 10cm long.
The FFC from the adapter board to the display also is 10cm long.
The adapter is one of these: https://github.com/RudolphRiedel/EVE_display-adapter/tree/master/L-D5019-08/L-D5019-08-02.
The supply is from a bench PSU that I set to 9V.
As the controller and the display both use 3.3V for the signals, the logic buffers on the adapter are not actually needed.
But what helps with performance across several development boards are the 56R series resistors.

I received a newsletter from Bridgetek on my work account that indicated that BT882 and BT883 are released, but I can not find any specifics for these.
Am I correct to assume that these are memory reduced variants of FT812 and FT813?
So like BT880 and BT881 but with 24 bit RGB interface?

Or are these BT815/BT816 or even BT817/BT818 with reduced RAM_G?

I very much prefer BT81x over FT81x for mostly three reasons, UTF-8 fonts, external Flash interface and ASTC compressed images.
And it seems like at least having ASTC would be a good idea when the size of RAM_G is reduced to a quarter.

On a slightly related note, do you have a list of display modules that are available for end users from different manufacturers?
I could probably compile such a list, but I am always on the lookout for something new to support with my library.

I just found that EAB 2.10.0 was released.

I went across it, converted images, verified images, converted a font, put that font in a flash container, packed that flash container with the asset compressor, converted the resulting .zopfli file with the BIN2C tool.
And this went very smoothly. :-)

I found one small issue though.
When converting fonts, the "Input Character:" file selection gets cleared every time a new font is selected.

Edit: just found 2.10.1 and the bug is still in while this post is still missing approval.
Edit2: and I just found 2.10.2 which is dated 2023-11-10.

I tried to use the PNG/JPEG Validator and found that the "VALIDATE" button is inactive unless I set the option "Generate Optimized File".
It still works when deselecting "Generate Optimized File".
But the "VALIDATE" button is inactive again when I remove the image and does not become active when adding an image.

This reminded me of your EVE-USB2SPI-KIT-B, are there plans to sell these thru DigiKey or Mouser and perhaps EVE4 series displays as well?
And I would like to buy an EVE4x-40G-IPS for my collection but shipping from Canada directly is a bit expensive while DigiKey and Mouser offer free shipping to EU and handling of the taxes beforehand.
Not asking for free shipping by Matrix Orbital, it's just so conveniant for me to order from Mouser or Digikey and I also can order a bag of other parts at the same time.
Most of my EVE2 and EVE3 series Matrix Orbital displays I ordered from Digikey or Mouser.

Edit:
Mouser is listing the EVE2-USB2SPI-KIT-B now, although there is no stock, yet.

I downloaded and installed EVE-Asset-Builder-setup-2.9_rc1.zip and I have an odd issue.

The button to open the explorer window to select the output folder is not working for me in "Asset Compressor" / "Compress".
When I use the button on the second tab "Validate" though it works, I can select the output folder, I have to confirm twice and
now the output folder is also changed on the "Compress" tab.