STM32F207 direct drive of LCD

[oe2]

Posted on February 07, 2012 at 21:22

I'm up for a new project, to save money on the LCD we are looking in to use a realy sheep display without driver. The resolution is 480x286 so I guess to display a simple static GUI using the FSMC would not be a big problem. We plan to add external RAM to be used as video memory, and use DMA to lower the load on the CPU. However the pixel clock for the display must be around 9MHz. Have any one done someting simular using STM32F207?

#stm32f207-lcd-driect-drive

[emalund]

Posted on February 09, 2012 at 15:55

Changing horses in the middle of the stream

.... usually get you wet I think you need to either bite the bullet and switch to another ARM or accept external display control I do not think you will see a dramatic price difference between a 'dumb' display plus an external controller with associated components and a display with the same controller built in. THUS, either switch to an ARM with a LCD controller or save a bunch of headaches and get the display and the controller as one package Erik

[Tesla DeLorean]

Posted on February 10, 2012 at 00:57

Some how I think the chip is too specialized and difficult to design around that it's not going to be at a retail distributor.

CPU load on approx 1% I think this is a bit deceptive, the bus loading will be significantly higher, which might be fine if you are not contending for access. For higher resolution, higher bandwidth displays, this will become crippling.

[oe2]

Posted on February 10, 2012 at 12:02

Thanks for the input.

[infoinfo980]

Posted on February 11, 2012 at 09:15

> I cant seem to find where to by SSD1963 I have tried Digikey, Farnell/Newark, Mouser.

http://www.techtoys.com.hk/

 have them for US$7 each. Of course if you want enough of them then Solomon Systech will be only too happy to talk to you.

[sjo2]

Posted on February 22, 2012 at 13:10

Just for info i have used the STM32/SSD1963 for a few ref designs, driving upto 10'' panels - it works well.

http://www.youtube.com/watch?v=SiGuGaEDeC8

Spen

[kobus]

Posted on May 23, 2012 at 09:44

for the sake of clarity, I'd like to know what the limiting factor is that would prevent one from using the STM32 to drive a larger display. To give some background, we have used LCD's with the STM32F207 in a few designs in the past, and thus have a reasonable investment in the platform. We would now like to upgrade one project to a 10''+ display from a 7'' one (with built in SSD1963). We've calculated that the SSD1963 could handle the resolution (800x600 16 bit) of the display we have in mind, but we cant seem to source this chip anywhere locally.

So again, we'd like to investigate the idea of using the direct connection method to see if this is possible. Surely it isn't necessary to go to an arm9/cortex A8 just to display some infrequently updated icons?!We intend to use a STM chip solely for display driving and can accept a lower refresh/pclk rate, so surely it should be possible if a 320x240 only uses 1% CPU load.If anyone has some input we'd appreciate it before we go on.      

[alok472]

Posted on May 23, 2012 at 10:10

so for 10'' TFT the resolution is 800x600 16 bit ?

Can you also check the TFT frame rate ? Normally that would define how many bytes need to be dumped on FSMC.

[Tesla DeLorean]

Posted on May 23, 2012 at 15:57

We intend to use a STM chip solely for display driving and can accept a lower refresh/pclk rate, so surely it should be possible if a 320x240 only uses 1% CPU load.

If anyone has some input we'd appreciate it before we go on.   

Again, I'm going to suggest this 1% is misleading. The limiting factor is the saturation of the external bus, via DMA, and your potential desire to access the frame buffer (1MB). Unless I lost the plot somewhere, the DMA does a Read then Write back-to-back. So you're bandwidth is halved immediately, toss in whatever number of cycles your memory/lcd is set to consume for the access. I don't think you can get it to do just a Read and throw the data away. ie say the LCD interfacing could snoop the external bus and grab the data directly as it comes out of the external SRAM. Look at the timings and do the math. The STM32 is simply not designed for driving dumb panels efficiently. Controllers which do either use internal frame buffers, or use SDRAM hung of separate buses (ie harvard style) and have signalling/clocks