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notro / fbtft

Linux Framebuffer drivers for small TFT LCD display modules. Development has moved to https://git.kernel.org/cgit/linux/kernel/git/gregkh/staging.git/tree/drivers/staging/fbtft?h=staging-testing
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Dual displays #403

Closed dave-lawrence-dev closed 7 years ago

dave-lawrence-dev commented 8 years ago

I have a project which requires a pair of small TFTs. My client is looking at the Adafruit ST7735R. Is it possible to connect two to the same RPi?

Thanks,

notro commented 8 years ago

Yes: https://www.youtube.com/watch?v=0vfDifIU7gw

dave-lawrence-dev commented 8 years ago

Thanks! Is this documented in a HOWTO?

notro commented 8 years ago

I haven't seen a Device Tree overlay for that display, but you can have a look at this: https://github.com/raspberrypi/linux/blob/rpi-4.4.y/arch/arm/boot/dts/overlays/pitft22-overlay.dts compatible should be "sitronix,st7735r" Then add a node for your second display.

The default gamma values for that driver is probably off for the adafruit display: http://lxr.free-electrons.com/source/drivers/staging/fbtft/fbtft_device.c#L276 You can probably use the 'gamma' DT property (string), but I have never actually tried it. See http://lxr.free-electrons.com/ident?i=fbtft_probe_dt

Info about the various properties can be found here: https://github.com/notro/fbtft/wiki/fbtft_device fbtft_device was made when Raspberry Pi didn't have DT support.

Refs: https://github.com/notro/fbtft/wiki/FBTFT-RPI-overlays https://www.kernel.org/doc/Documentation/devicetree/bindings/spi/spi-bus.txt https://github.com/notro/fbtft/wiki/Debug

dave-lawrence-dev commented 8 years ago

Hi,

after a little break I am back on this project. I now have two Sainsmart 1.8" displays and using your wiring,

"dtparam=spi=on" in /boot/config.txt

and "modprobe fbtft_device name=adafruit18 rotate=90"

I have a working display using current debian jessie on a RPi 3B.

Please can talk me through what is necessary to fire up the second display? How do I wire it? what extra config is needed to make [I guess] /dev/fb2?

Many thanks,

On 23/07/16 11:07, notro wrote:

I haven't seen a Device Tree overlay for that display, but you can have a look at this: https://github.com/raspberrypi/linux/blob/rpi-4.4.y/arch/arm/boot/dts/overlays/pitft22-overlay.dts compatible should be "sitronix,st7735r" Then add a node for your second display.

The default gamma values for that driver is probably off for the adafruit display: http://lxr.free-electrons.com/source/drivers/staging/fbtft/fbtft_device.c#L276 You can probably use the 'gamma' DT property (string), but I have never actually tried it. See http://lxr.free-electrons.com/ident?i=fbtft_probe_dt

Info about the various properties can be found here: https://github.com/notro/fbtft/wiki/fbtft_device fbtft_device was made when Raspberry Pi didn't have DT support.

Refs: https://github.com/notro/fbtft/wiki/FBTFT-RPI-overlays https://www.kernel.org/doc/Documentation/devicetree/bindings/spi/spi-bus.txt https://github.com/notro/fbtft/wiki/Debug

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notro commented 8 years ago

You have to at least add one of the display using Device Tree to make it work. fbtft_device can only add one device. Maybe this can be of help: https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=109065

dave-lawrence-dev commented 8 years ago

Hi,

Thanks for the pointer, I've made the overlay work {including the "status="ok"" fix described} for a single display. For two displays, do I wire up SCL/SDA/CS/5V/GNC in parallel? and then separate DC and RES GPIO's?

Your patience is much appreciated; this is all new ground for me. I've never worked with overlays or device trees before.

On 27/08/16 11:50, notro wrote:

You have to at least add one of the display using Device Tree to make it work. fbtft_device can only add one device. Maybe this can be of help: https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=109065

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. Dave Lawrence . Tel: +44 1628 491960 . Net: dl@alphawave.net . | Alphawave Ltd | Tel: +44 7768 224315 | Web: www.alphawave.net |

notro commented 8 years ago

You need separate CS, Chip Select, as well.

dave-lawrence-dev commented 8 years ago

Hi,

Thank you, I connected up to SE1 and set the reset and DC GPIOs to 23 and 18 and it's working!

At least on loading static images with 'fbi', I've not tried anything more advanced (X or QT as descrived by Hydrael)

I'm sure a HOWTO and FAQ on your your wiki would be well received.

Best regards,

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notro commented 8 years ago

I'm sure a HOWTO and FAQ on your your wiki would be well received.

Anyone with a github account can edit the wiki ;-)

notro commented 7 years ago

Closing issue since there has been no activity in a long time. Reopen if needed.