notro edited this page Jun 22, 2016 · 150 revisions

Linux Framebuffer drivers for small TFT LCD display modules.

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Raspberry Pi SPI DMA

To maximize throughput, make sure txbuflen is 16k or 32k (default is usually 4k). This is needed because of the DMA mapping/engine overhead per transfer that spi-bcm2835 has.

Device Tree: txbuflen = <32768>;
fbtft_device: txbuflen=32768

# Here it is 16k
$ dmesg | grep graphics
[    8.547173] graphics fb1: fb_ili9341 frame buffer, 320x240, 150 KiB video memory, 16 KiB DMA buffer memory, fps=50, spi0.0 at 48 MHz

See /boot/overlays/README and FBTFT RPI overlays for information about Device Tree overlays.

To use fbtft_device instead of a DT overlay, add to /boot/config.txt:


Step-by-step using FBTFT (without Device Tree)

Using the Adafruit 2.2" display as an example

Enable driver

Register device (the driver will load automatically)
sudo modprobe fbtft_device name=adafruit22

dmesg will show the default pin assignements, and that the driver is loaded.

   fbtft_device:  SPI devices registered:
   fbtft_device:      spidev spi0.0 500kHz 8 bits mode=0x00
   fbtft_device:      spidev spi0.1 500kHz 8 bits mode=0x00
   fbtft_device:  'fb' Platform devices registered:
   fbtft_device:      bcm2708_fb id=-1 pdata? no
   fbtft_device: Deleting spi0.0
   fbtft_device:  GPIOS used by 'adafruit22':
   fbtft_device:    'reset' = GPIO25
   fbtft_device:    'led' = GPIO23
   fbtft_device:  SPI devices registered:
   fbtft_device:      spidev spi0.1 500kHz 8 bits mode=0x00
   fbtft_device:      fb_hx8340bn spi0.0 32000kHz 8 bits mode=0x00
   graphics fb1: fb_hx8340bn frame buffer, 176x220, 75 KiB video memory, 16 KiB buffer memory, fps=20, spi0.0 at 32 MHz


X Windows
FRAMEBUFFER=/dev/fb1 startx

Note: You might need to move an xorg config out of the way if X doesn't start:

sudo mv /usr/share/X11/xorg.conf.d/99-fbturbo.conf ~
con2fbmap 1 1

Make it permanent (Debian Jessie, Arch Linux, systemd)

Add to file /etc/modules-load.d/fbtft.conf


(the auto loading of spi-bcm2835 is too late for fbtft_device to find the spi bus, so it has to be manually loaded)

Add to file /etc/modprobe.d/fbtft.conf

options fbtft_device name=adafruit22


Without the help from other people, this project would not exist

  • Matt Porter wrote st7735fb which FBTFT grew from
  • Texy has provided much input and testing that have helped move this project forward
  • Derek Campbell did the work to implement DMA
  • Several people have provided drivers and improvements
  • Donations have helped me buy displays and accessories

Also thanks to people that help answering questions about FBTFT.