ekondratiev

Hello! After one month of testing the approach from AN and documentation (see my message from September, 27) display works OK. No glitches even if use SDRAM for working data buffers.

Hello! Hope it helps but I would wounder what are these unpredictable conditions causing HW displat controller (LTDC) to miss its sync? It runs under the debugger step-by-step run even. So, as I was written before I looked into the clocks and MPU (caches) configuration. Changed clocks to 200 HCLK and 100 for APB1, turned off the Overclock, enabled BURST in SDRAM and specified the MPU region for video memory to WT. Yesterday it worked well. I will look at it next days. I had no critical sections in my code but only ..Suspend and .. Resume the scheduled during the videobuffer switch (part 4.4.2 in STM AN4861).

Exactly the same as I get. But for 746 I've found the place with floating points calculation. At first I've fount that atan2() causes the glitch and than found out the reason. But The glitch could happen once per hour and now I think that this is a question of caches. Try to disable D-Cache and check. Have you looked at AN4861, AN4838 and AN4839 documents from ST? There are very interesting parts in AN4861 (4.6 Special recommendations for Cortex®-M7 (STM32F7 Series), 6.2.7 MPU and cache configuration - especially for M7 core). I've read it carefully and wrote down some points to try. Moreover, it is said that CPU clock should be 200 MHz maximum (where SDRAM clock will be 100 Mhz) and I run it at 216...

Hello! I'm out of my machine these days and will continue test on Monday. But befre that I will read about the caches and LTDC appnote in the part of Cortex-M7 specialities. Will do some videos on Monday/Tuesday and upload it here. I think that some operations inside M7 core cause LTDC lines/frame refresh process to halt for a little and this does glitch on the screen or this is the data cache problem. Will read about this... I've spent some days with 746 and found out that __arm_eabi_f2d (not remember the name exactly, but this is the function/intrinsic to convert floats to doubles) causes the glitch. Sometimes... But when it happens it real happen when you go one step thru it in debugger. Just "Step over" and the display flickrs.

Hello! I have exactly the same issue but with my own graphics library. I've asked in ST forum here (https://community.st.com/message/169193-stm32f7-ltdc-flickering) and described some details as well. So, I have a solution for 746 but still have no for 767. Disabling D-Cache helps but I would prefer to have the full performance there.

Oh, I have a question. Is it possible to make a pixmap 4-bits per pixel? To store 2 pixels in one byte. Or 8bpp is minimum?

Ok, I just hadn't found it :-)

Thank you!

I try to prototype the device with external e-ink displays which will be connected thru Ethernet or so. And these displays will show some "windows" with information. Okey, I'll try to implement such a big pixmap and some "renderPixmap" function to update all the screens.

Hello! I need to draw one big image (a set of smaller pictures) across several displays. So, one picture could be cut by these displays. It's like Windows windows on two monitors. You can move, for instance, Chrome window as left part of it is displayed in one monitor, and right part on another. I plan to run it under Linux on Raspberry Pi (or something similar) without X Windows and I have monitors, connected by Ethernet with some high level slow interface. RAM should be enough, so I think that pixmap buffer could work well.

Thank you for quick reply! I need to display one big image (in fact, the set of different images in one big field) on multiple displays. So, this big image must be splitted by parts to be displayed. As far as I understand, I could use pixmap and than split it inside the display driver module and than send to different displays. But in this case I need to check the changes and find out which displays are needed to be updated because the connection to these displays is rather slow. Am I right? Thank you in advance, -- Eugene

Hello! Could you help me? I try to make some kind of splitted screen. Just to draw images or lines on some one framebuffer image and than display it on two displays. Is it possible with uGfx?