STM32F479 datasheet(67/91 Pages) STMICROELECTRONICS

67 / 91 page

DocID029237 Rev 2

67/91

AN4861

LTDC application examples

For the 24 bpp color depth and in a double framebuffer configuration, the required

framebuffer size exceeds the internal SRAM size (2 x 382.5 Kbyte), so using an external

SRAM or SDRAM is a must for this configuration.

The next step is to check if the SDRAM 16-bit bus width can sustain the desired resolution

and color depth.

Check if a 480 x 272 resolution with 24 bpp fits the SDRAM 16-bit

configuration

At this stage the user should have decided to use an external SDRAM but still has to check

if the SDRAM 16-bit bus width (actual hardware implementation in the discovery board)

matches the 480 x 272 @ 60 Hz display size and 24 bpp color depth.

In order to conclude if such hardware configuration can support the desired display size and

color depth or not, the user should first compute the pixel clock.

The computed LCD_CLK is about 9.5 MHz (for computing pixel clock refer to Section 6.2.3:

LTDC GPIOs configuration.

Then the user should check based on the following parameters if the computed pixel clock

is not higher than the maximum LCD_CLK indicated in Table 11.

–

Number of used LTDC layers: in this example only one layer is used.

–

System clock speed HCLK and framebuffer memory speed: HCLK @ 200 MHz

and SDRAM @ 100 MHz.

–

External framebuffer memory bus width SDRAM 16-bit.

–

Number of AHB masters accessing concurrently to external SDRAM: 2 masters

(DMA2D and LTDC).

Referring to the pixel clock Table 11 in the “LTDC + DMA2D” column and one layer row, the

pixel clock can reach 34 MHz for SDRAM of 16-bit.

So the SDRAM 16-bit bus width is quite enough to sustain a 480 x 272 @ 60 Hz resolution

(LCD_CLK = 9.5 MHz) with 24 bpp color depth.

6.2.3

LTDC GPIOs configuration

As shown on Figure 34, the ROCKTECH RK043FN48H display is connected to the

STM32F746xx using a parallel RGB888 of 24 bits.

LTDC RGB interface pins configuration

Once that the STM32CubeMX project is created, in the Pinout tab choose one from the

listed hardware configurations. Figure 36 shows how to select the RGB888 hardware

configuration with the STM32CubeMX.

The user can also configure all the GPIOs by setting the right alternate function for each

GPIO one by one.

STM32F479 датащи(PDF) 67 Page - STMicroelectronics

STM32F479 датащи(HTML) 67 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91

датащи скачать

ссылки URL