Can't get I8080 code migrated from 0.20.1 to 0.21.0 to work properly

[yanshay]

I'm developing an application, pretty large, that uses I8080 for display.
Up to version 0.20.1 it worked.
0.21.0 introduced changes to how work with I8080 takes place. I migrated my code, same data is sent out using DMA, exactly the same methods only with the API changes.

Well, it doesn't work properly. Instead of seeing the the proper UI, I see pixels drawn to screen to a smaller square that shows on the bottom right of the display.
So it seems to me like the display is getting the wrong data in some of the dma commands. I spent hours trying to figure out what's going on there but so far can't find what it is.

So I wonder, have there been any changes except the API structure of using the DmaTxBuf and transfer, etc. ?
Maybe some underlying I8080 data that was sent in previous API and now moved out and in the responsibility of the application?
Maybe timeout changes?
Or anything else that my code relied on that's now different?

BTW - the i8080 example works properly on my device, but my program is much more complex and works completely different with the display than the simplistic demo.

Thanks

[Dominaezzz]

Nothing should've changed with regards to the implementation. Make sure you don't forget to call DmaTxBuf::set_length, there's a chance you're not sending out all the data you think you are.

Are you using the Bus wrapper (in the example) in your project? Or are you doing more fun DMA buffer stuff yourself?

[Dominaezzz]

The MADCTL command should have a parameter for this.

What's MADCTL? Any pointers to this?

https://www.displayfuture.com/Display/datasheet/controller/ST7796s.pdf

[yanshay]

I Opened issue #2362

[Dominaezzz]

I've setup slint myself now and the madctl suggestion won't work by itself, you'd also have to swap the bit order on the i8080 driver.

This should let you use the public code for now.

Of course you will have to undo the swap when you send commands and redo the swap when you send data.

Having written the platform trait, I now understand the optimization you're talking about. I'm curious how often in reality you hit that code path. I guess if everything is rectangular.

Now I just need to figure out the touch screen on this thing.

[yanshay]

I ended up switching the byte order only outside the public code ( so only the line that was in previous release which is if I get it right the byte order in case of 8 bits mode). I understand the reason for the change was that the decision on word size was moved to transfer time, but seems like in reality it has to be decided at initialization of the i8080 due to this setting (or switch on on every transfer which might be expensive).

And with that setting it works just fine.

That optimization takes place pretty frequently because slint redraws the rectangle size where changes took place since last redraw. So I definitely see high rectangles being drawn and could avoid several hundred short dma bursts every such rectangle.

The interesting thing with slint is that it's line by line drawing using the software rendered is (at least was) faster than the full screen render, I told them that and they checked and agreed it was strange but seems like their optimizations for the single line drawing were very effective.

As for the touch, I am using a public crate that I found and only added some async support for utilizing the interrupts. Let me know if you have questions regarding that.

[Dominaezzz]

but seems like in reality it has to be decided at initialization of the i8080 due to this setting (or switch on on every transfer which might be expensive).

Yeah this is a tough one, ideally one shouldn't have to recreate the driver to change this setting. I think exposing a different method for each setting might be the way to go. Keep it simple.

because slint redraws the rectangle size where changes took place since last redraw

Oh neat, I'll implement the optimisation as well then.

The progress bar animation has been pretty smooth, I'm looking forward to see how far I can push this with the animations.