I'd like to have a 3.5 inch LCD screen hooked up to my Raspberry Pi and also to the TV through HDMI with both screens displaying the same thing at all times.
Is this possible yet without getting super tech into it?
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1 Answer
It's not possible, at least with official LCDs. As explained here, only one screen on the RPi can have a framebuffer, which is needed for most GUI apps. Only some videoplayers (which use hardware video decoding) and games (which draw on the screen using GLES) are capable of using a second screen simultaneously, and that mode is not screen duplication either.
However, there are people who managed to get their (SPI) LCD screens to work in parallel with HDMI. See this for example. As far as I understand, SPI screens have their own drivers independent of the videocore, so they can have allocate regular RAM as additional framebuffer devices.
Also bear in mind that many HDMI screens simply don't support typical touchscreen resolutions like 480x320 or 800x480. I know my screen doesn't, since I have tried doing what you want with a Banana Pi (which can use both video outputs at once).
answered Mar 1, 2017 at 11:41
