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STM32 F469-DISC0 change display resolution, LTCD frequency

Bladl
Associate

Hello!

Q1: We wonder if it is possible for evaluation to change the resolution from 800x480 to something like 640x480 (or even 320 x 240) on the f469I-DISC0 by changing parameters.

The screen should then show black 80 pixel to the left and 80 pixels to the right, the active screen should be positioned in the middle (like on a standard monitor).

Reasons to do so:

- target application does just need lower resolution

- remarkable memory saving (e.g. using internal SRAM)

- saving 20% (640/800) bus bandwidth can have an impact while evaluating for a 640 x 480 solution. With 800 x 480 we already have issues with DMA2D (we need to set the "DeadTime" to a value of 230 to avoid "bucking").

- higher framerates for nice animations

We played already with values for horizontal front- and back porches (""nt35510.h"), in the hope, this produces the black bars on the left and right side but with no positive effects, there are no black bars at all...

 

Q2: We were able to change the frequency of the LTCD to 38400MHz (384MHz / 5 / 2) for to have a higher framerate. This seems to work but of course we wonder, what the maximum frequency for the LTCD is? The "normal" TFT-LCDs (24 bit parallel control) have a range up to approx. 36MHz. But here we have this "DSI-LTCD-Blackbox" combination that makes it hard to anticipate the correct settings (what we try and what happens does often not correspond...).

 

Q3: For the "STM32H747I-DISCO" there exists an DSI-HDMI adapter to connect the board to an external monitor.

Do you know:

a) where to buy this adapter?

b) if this adapter can be connected to the board to replace the internal display of the "STM32F469I-DISC0", in other words, is it (that way) possible to connect a HDMI monitor to the F469-DISC0 Board?

 

Thank you and best regards!

1 ACCEPTED SOLUTION

Accepted Solutions

https://www.st.com/en/evaluation-tools/b-lcdad-hdmi1.html

Mouser, DigiKey, etc

https://www.mouser.com/ProductDetail/STMicroelectronics/B-LCDAD-HDMI1

The STM32F469I-DISCO is not designed for screen removal. The EVAL boards might have more options, you're working with a relatively old design.

The DSI supports 2 lanes at 500 Mbps (1Gbps), figure 1280x1024x24x60 is like 1.8 Gbps, so will need to drop colour depth, or refresh rate

1000 / 16 = 62.5 MHz (16-bpp) Max Pixel Clock w/DSI

1000 / 24 = 41.667 MHz (24-bpp)

Should be able to get slightly north of 63 MHz on LTDC, but would likely want 32-bit SDRAM width, as that will likely be the secondary constraining parameter.

The off-load rate on the DSI needs to be at least as fast as the generation rate on the LTDC

 

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View solution in original post

1 REPLY 1

https://www.st.com/en/evaluation-tools/b-lcdad-hdmi1.html

Mouser, DigiKey, etc

https://www.mouser.com/ProductDetail/STMicroelectronics/B-LCDAD-HDMI1

The STM32F469I-DISCO is not designed for screen removal. The EVAL boards might have more options, you're working with a relatively old design.

The DSI supports 2 lanes at 500 Mbps (1Gbps), figure 1280x1024x24x60 is like 1.8 Gbps, so will need to drop colour depth, or refresh rate

1000 / 16 = 62.5 MHz (16-bpp) Max Pixel Clock w/DSI

1000 / 24 = 41.667 MHz (24-bpp)

Should be able to get slightly north of 63 MHz on LTDC, but would likely want 32-bit SDRAM width, as that will likely be the secondary constraining parameter.

The off-load rate on the DSI needs to be at least as fast as the generation rate on the LTDC

 

Tips, Buy me a coffee, or three.. PayPal Venmo
Up vote any posts that you find helpful, it shows what's working..