LPC1769@120MHz, emWin, 320x240 TFT based on ILI9341 in 16-bits parallel bus: how fast is a full refresh?

[lpcware]

Content originally posted in LPCWare by giusloq on Thu Apr 30 09:22:05 MST 2015
Video

Please, ignore the quality of video.

What do you think? Could it be faster?

Subject is complete. I'm using emWin libraries on LPC1769 (OM13000 developer board) running at 120MHz (4MHz from IRC and main PLL configured with multiplier 45 and divider 3).
The interface with 320x240 TFT is 16-bits parallel bus.

I'm using GUI_DrawBitmap() every 1 second to draw a 320x240 image (full screen).

I expect a better performance.

[lpcware]

Content originally posted in LPCWare by giusloq on Fri May 01 03:02:21 MST 2015
LPC1785 has smaller Flash so I think the problem of code space is similar, except if you use an external Flash memory increasing cost, board space and complexity.
Of course my application is simple so I don't have many images so I hope the internal Flash is sufficient for all.

Unfortunately I must use 2.4" Tft because it must enter in a already designed plastic enclosure. And it's strange but I can find several chinese TFT display with parallel interface at a price about 5usd, and a few 2.4" tft with rgb intrrface at a price of about 15usd.

Please, could you help me with DMA method? I never use it. I just filled the functions used by emWin ILI9341 display driver. Those functions simply change the display pins high/low state.

[lpcware]

Content originally posted in LPCWare by wmues on Fri May 01 01:17:01 MST 2015
Yes, you will need a SDRAM.
But even WITHOUT the requirement for a local framebuffer, you will need a lot of storage:
- code of the window library
- font engine storage
- pictures, icons, etc
- drawing surfaces.

I have done a LPC1785 QFP208 design with 16bit SDRAM on 2 layers, SDRAM clock is 78MHz. Working fine.
LCD is 3,5" TFT, used with RGB565, which is the cheapest "standard" TFT LCD. With resistive touch.

If you want to stay with your approach, the best solution would be to use the DMA controller to transfer the data to LCD.
DMA can move larger blocks of data faster than the CPU.

[lpcware]

Content originally posted in LPCWare by giusloq on Thu Apr 30 14:31:46 MST 2015
I know, but it is a completely different approach.

Using integrated TFT controller means having a big RAM to store framebuffer. This means at least a SDRAM connected on a high speed bus. Maybe this means 4 layers PCB. A more expensive micro.

It's strange but it is very difficult to find a good TFT 2.4" display with RGB interface at a reasonable price. Most of them provide only parallel MCU interface.

At the moment I'd like to stay with this solution and try to reach the best performnce that is possible to obtain.

[lpcware]

Content originally posted in LPCWare by wmues on Thu Apr 30 13:24:23 MST 2015
Use a LPC1785 and a TFT without a framebuffer. It will be much faster.