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ST7703 send commands with video mode, question #27

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jrebsse opened this issue Jul 12, 2024 · 1 comment
Open

ST7703 send commands with video mode, question #27

jrebsse opened this issue Jul 12, 2024 · 1 comment

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@jrebsse
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jrebsse commented Jul 12, 2024

Hi,
your articles are awsome. Thanks for that.
I got a question regarding the notes section of src/dsi.md .
There it says in lines 724-727:

1.  ST7703 always runs in __DSI Video Mode__ (instead of Command Mode).

    Does this mean that all DCS Commands are sent over all 4 DSI Data Lanes? (Instead of DSI Lane 0 only)

The note is written as a question and i'm wondering is it like that, that all commands are sent over 4 DSI Data Lanes ?
The default configuration of the ST7703 is to use 4 lanes. In my use case i only got 2 lanes which means that i can't configure the ST7703 to use only 2 lanes through the MIPI DSI Interface ?

@lupyuen
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lupyuen commented Jul 13, 2024

Hi: Thank you so much for reading my articles! Sorry I made a mistake, here's how ST7703 actually works on PinePhone and other MIPI DSI Devices:

  • At Startup: DCS Commands are sent over DSI Lane 0 to init the ST7703 Display Controller. Only DSI Lane 0 is Bidirectional (not the other DSI Lanes) and supports DCS Commands.

  • After Startup: Pixel Data is sent over Multiple DSI Data Lanes, in Video Mode. Which means the Pixel Data is pushed as a continuous stream of Video Pixels, instead of plotting every pixel command by command.

So 2 DSI Lanes are perfectly OK, we only need Lane 0 to configure the ST7703 Display Controller. Both DSI Lanes will be used to push pixel data later.

I have corrected the text in my article. The correction will also make my article consistent with this section: https://lupyuen.github.io/articles/dsi#connector-for-mipi-dsi

Are all 4 DSI Data Lanes identical?
For sending commands to the Display Controller, only DSI Lane 0 is used.

Thanks! :-)

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