STM32F207 and WVGA 7 inches TFT LCD

[johann23]

Posted on January 16, 2012 at 11:25

Hello,

I plan to use a STM32F207 MCU in order to display pictures stored in a SD card on a controller-less 7 inches TFT display (WVGA, 800x480, 18bpp). The pictures are static. Is it possible to interface such a display with the STM32F207 without the use of an external LCD controller? If yes, what should I be aware of in order to implement this STM32F207 based TFT LCD controller (SRAM speed, SDIO speed, ...)? If no, what are the other solutions (obsolescence is a major factor)? Note: the STM32F207 will be used for other purposes too and the TFT LCD display is the Hitachi TX18D35VM0AAA. Thank you, Johann #stm32-tft-lcd-controller

[balmukund66]

Posted on January 16, 2012 at 12:34

I have tested the same you are describing for QVGA (320X240) 16 bpp.

For me  SRAM size is 4 Mbits. access time of SRAM 55 ns. & STM32F20xx is used for other purpose also. For your Application  the SRAM size will be more(It should be sufficient enough to store two image   ,for wvga  SRAM size should be slightly more than 800x480x18 bits  x2 ).  Even on this access time , you can achive very high frame rate. Regards Balmukund Prasad

[johann23]

Posted on January 16, 2012 at 13:59

Thank you for your answer.

I agree with you for the SRAM size but the 55ns access time would be too slow for a pixel clock of 30MHz, isn't it? Best regards, Johann

[Tesla DeLorean]

Posted on January 16, 2012 at 15:30

I agree with you for the SRAM size but the 55ns access time would be too slow for a pixel clock of 30MHz, isn't it?

Yeah, I'm hard pushed to see you having the bandwidth to direct drive such a screen. The external bus is 60 MHz max, and half of that will disappear to the screen, the other to the memory, with no margins. Have you considered a micro that is actually designed to direct drive TFT displays of this size? You'd presumably want a micro that supports SDRAM and TFT-LCD natively. Have you looked at the LPC1788? Obsolescence is a huge problem, what time frame are you talking about? The rate un-economic lines are getting killed you want a design that is flexible/adaptable.

[johann23]

Posted on January 16, 2012 at 16:09

• The external bus is 60 MHz max, and half of that will disappear to the screen, the other to the memory, with no margins.

Yes, designing with no margins is not a good idea and not an option.

• Have you considered a micro that is actually designed to direct drive TFT displays of this size?

Not yet but it can be interesting, if production life time is long enough. Do you have any experience with such MCUs?

• Have you looked at the LPC1788?

No. I'll take a look at it.

• Obsolescence is a huge problem, what time frame are you talking about?

5+ years.

[rmteo]

Posted on January 16, 2012 at 16:36

Plus if you go with the LPC1788 (also the LPC18XX and LPC43XX which run to 204MHz and have unique peripherals such as SPIFI, SDRAM, SGPIO, SCT, etc.), you get to use the Segger emWin Graphics Library for free. 

See video

http://www.youtube.com/watch?v=KsnPmN5V2M8&feature=related

[johann23]

Posted on January 17, 2012 at 10:16

I will consider the LPC1788, it is more convenient for my target application Furthermore, as you said, there are some ''plus'' such as the free graphic library.

Thank you for your answers. Regards, Johann