Lomax
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Can an LCD share the SPI bus with another device

Tue Jan 15, 2019 9:55 pm

Sketching on a portable device based on the Pi Zero W, for which I'd like to use a Sharp "Memory LCD" display. These have a SPI interface, and should work with the FBTFT framebuffer. But I have another device I'd like to include, which also uses SPI, and only SPI0 will be free. Can the LCD share the bus with another device without issues, or will it kill the framerate (not that MIP type displays are particularly snappy), or cause other issues?

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DougieLawson
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Re: Can an LCD share the SPI bus with another device

Wed Jan 16, 2019 12:25 am

There's two SPI buses and five chip select (chip enable) pins on the 40 pin header. You can have five SPI devices.

https://pinout.xyz/pinout/spi
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Lomax
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Joined: Wed May 20, 2015 9:43 pm

Re: Can an LCD share the SPI bus with another device

Wed Jan 16, 2019 8:29 am

DougieLawson wrote:
Wed Jan 16, 2019 12:25 am
There's two SPI buses and five chip select (chip enable) pins on the 40 pin header. You can have five SPI devices.
Yep, SPI0 with two chip select and SPI1 with three. But I need the SPI1 pins for other use (I2S audio) so only have SPI0 and CE0/CE1. I'm worried that toggling between the LCD and another device will cause display issues like flickering, tearing or low framerate. I've never tried sharing a SPI bus with a display before...

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DougieLawson
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Re: Can an LCD share the SPI bus with another device

Wed Jan 16, 2019 10:23 pm

Try it, it's the only way you'll find out for sure.
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