EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ricko_uk on April 23, 2022, 08:21:07 pm
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Hi,
first time designing with ILI9488: elecrow.com/download/ILI9488%20Data%20Sheet_100.pdf
I am using MCU data bus interface (18-bits wide). On page 137 it says "Normally, the ILI9488 has no frame buffer of its own, so all image data shall be supplied by the host processor at a
sufficiently high rate to avoid flicker or other visible artifacts."
That wording implies that the controller itself doesn't have a frame buffer BUT that paragraph is under the DSI Transmission Data Format and nowhere else anything similar is mentioned. That would imply that it is somehow relevant only to the DSI bus interface - which I am not using - and not to the MCU or RGB interfaces. Is that so? How can that be?
If I am using MCU or RGB interface and want to display a static image, do I have to continually update the display? That seems absurd...
Also not sure why it says "Normally it has no frame buffer of its own". The display I am using does not mention anything about buffer. Datasheet attached below.
Many thanks :)
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It's a bit confusing, but possibly because of the language barrier, so the translation is not ideal.
This controller has GRAM as stated in the DS. The confusion comes from the fact that you're looking at the DSI interface, which is one of the interfaces this chip offers, and which is basically a constant stream of data such as for HDMI, if you will. In this mode, you're supposed to constantly feed the controller with pixel data in the right order, or it will stop displaying properly. Like an HDMI monitor.
Unless you have a particular reason for using DSI, you should use one of the parallel MCU interface modes (or SPI). In those modes, you can only update the GRAM content and issue commands, and you don't need to constantly feed the display with new data if the image doesn't change.
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It's has framebuffer of 320x480x18bpp, but used in mcu bus mode (8080, 6800), it's very different from RGB or DSI, these provide the pixel clock, data, sync... interfacing the lcd matrix directly.
You can see RGB or DSI as HDMI or displayport. They provide a constant flow of data.
If you want to send data only when required, you should use mcu bus mode.
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Thank you SiliconWizzard and David
now it does make sense! :)