STM32F4 LCD direct drive

[kqian]

Posted on November 26, 2014 at 19:13

I am going to use STM32F429 to control the  LCD with 800*600 resolution. The datasheet shows STM32F4 has an integrated LCD controller. Anyone can tell me how to use that controller to drive the LCD without adding extra LCD controller?

#freq #tft-ltdc-stm32f429-color-format #ltdc #stm32f429

[waclawek.jan]

Posted on November 26, 2014 at 22:45

Have a look at the '429 DISCOVERY for an example.

JW

[louislee]

Posted on November 28, 2014 at 02:51

Hi all,

I've inquired a free STM32F429ZI sample for driving a 10'' LCD supporting XGA 1024*768 with 65MHz refresh rate. In the STM32F429ZI datasheet, it describes that LTDC clock output frequency is 42MHz. And then I use STM32CubeMX to configure parameters, but it's possible to set LCD-TFT clocks 65.x MHz. It confuses me!!

About the configuration of STM32CubeMX, is it a correct, a bug or anything else? Hope anyone can help me.

Best Regards,

Louis Lee

[Tesla DeLorean]

Posted on November 28, 2014 at 03:30

I'd imagine it's Cube's failure to adequately scope the variables. I'd suspect the number is between 42-45 MHz depending on the SDRAM speed (84/90MHz) and that of the processor (168/180MHz)

Suggest you inquire with an FAE as to the hardware limits, and to the appropriate forum for Cube bugs.

[Tamas Novak]

Posted on November 28, 2014 at 19:44

I think all depends on the color scheme: if using 1byte/pixel (e.g. L8: 256 colors  with CLUT), the 65MB/s bandwidth is easily accessible by 16 or 32bit FCM external memory access. 2byte/pixel (e.g. RGB5-6-5 color format) is still reachable: 130MB/s-> 33MHz/32bit at external SRAM or SDRAM.

[Tesla DeLorean]

Posted on November 28, 2014 at 20:40

The poster did quote MHz, and it's not uncommon for those size panels to push 170-230 MBps at the probable colour depths in use here, with a clock of 65 MHz

I'd expect the STM32 to need a panel with a lower refresh rate to get the clocks reined in sufficiently. ST staff very may well have a list of known-to-work panels.