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LTDC clock problem

yassineelkhadiri
Associate
Posted on October 22, 2015 at 17:51

Hello,

I'm targeting the STM32F429IIT6. I have a problem with the LTDC driver clock. I'm trying to drive this 800x480

http://www.newhavendisplay.com/specs/NHD-7.0-800480EF-ATXL-CTP.pdf

at 30 fps. In my system clock configuration, I have something like this :

PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_LTDC;
PeriphClkInitStruct.PLLSAI.PLLSAIN = 120;
PeriphClkInitStruct.PLLSAI.PLLSAIR = 4;
PeriphClkInitStruct.PLLSAIDivR = RCC_PLLSAIDIVR_4;
HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct);
HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

With this I get a display with a visible scan line like shown

http://imgur.com/ZRgDCOG

(120/4/4 = 7.5 MHz for the pixel clock). According to the datasheet, the maximum pixel clock supported is 50MHz (from which we are quite far). As soon as I try to bring the pixel clock a little higher :

PeriphClkInitStruct.PLLSAI.PLLSAIR = 2;
PeriphClkInitStruct.PLLSAIDivR = RCC_PLLSAIDIVR_4;

or :

PeriphClkInitStruct.PLLSAI.PLLSAIR = 2;
PeriphClkInitStruct.PLLSAIDivR = RCC_PLLSAIDIVR_2;

I get

http://imgur.com/VzYVCDu

. Am I doing something horribly wrong? #stm32f429-ltdc-lcd-tft-clock
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