Has there ever been a solution to this problem? Is there any answer from bridgetek?
No, yes and maybe.
No, since as far as answers from Bridgetek, this is it, the thread went dead.
Yes, and this is based on experience since then, not on real hard data.
While the flash connected to the BT81x allows to display images directly, there is a caveat.
First off all, the bandwidth for the QSPI attached NOR flash is limited, naturally.
And this is not only limited by the clock of the QSPI but also latency when loading different assets since
reading something requires to address the flash first.
As I understand it, the pixel engine works thru the whole display list for every single line to be displayed.
So, there is a limit up to which this works as a product of the total bandwidth, the amount of data to be read per asset
and how many assets are supposed to be read, this is just a physical limitation.
Ok, yes, EVE-4 was improved and can prolong the time spent a pixel line but this reduces the refresh rate.
My advice from this is, pretend displaying anything directly from flash is not working at all.
Make use of all RAM-G before you try even try this and if you run out of RAM-G check what options you have
before starting to display anything from flash, like using ASTC for everything and check if the higher compression variants work for you.
Heck, ASTC-8x8 gave us full color plus alpha with only 2 bits per pixel while still looking good, this is like RAM-G getting 8x as large.
Not because displaying from flash is not working in general, but because it is a finite resource.
This brings me to the maybe.
Given that I had the most issues with one particular brand and model, my conclusion is that there is probably
some issue with the layout of that board between the BT815 and the flash.
There might have been reflections on the QSPI due to an impedance mismatch, so a layout issue.
But I will never know as I do not have the proper equipment to really measure a 36MHz QSPI.
My only real hint is that I used BT81x modules from three other brands and these allowed to push things further.
And looking forward we have this:
https://brtchip.com/bridgetek-is-in-embedded-world-2024-austin-texas/EVE-5 is launched at Embedded World in Austin, Texas in five weeks.
I have no idea what is coming (why oh why?
) - but it has been a few years since BT817/BT818 was launched.
I even checked if I could attend the fair, but the 11 hour flight was a no-go for me.
