Yocto Recipe to install FBTFT driver for Intel Galileo (gen1 and gen2)

This recipe will install fbtft driver (Commit #71994224c5ed951eab7ca9da2c919456d1632d15) with patch to disable dma. Full fbtft driver source can be downloaded from https://github.com/notro/fbtft.

The usage below is specific to Intel Galileo Gen 1 & Gen 2 only.

Pre-requisite

Please ensure the yocto kernel has the following config options enabled before proceed:

FB_SYS_FILLRECT
FB_SYS_COPYAREA
FB_SYS_IMAGEBLIT
FB_SYS_FOPS
FB_DEFERRED_IO
FB_BACKLIGHT

Usage:

Copy the contents in the "recipe/" folder to /meta-clanton_vX.Y.Z/meta-clanton-distro/recipes-kernel/*.

Append the line IMAGE_INSTALL += "fbtft-driver" to the files listed below:

/meta-clanton_vX.Y.Z/meta-clanton-distro/recipes-core/images/image-full.bb
/meta-clanton_vX.Y.Z/meta-clanton-distro/recipes-core/images/image-spi.bb

Once done, enter the following command in the yocto build environment:
```
~$ bitbake fbtft-driver -c build
```

Rebuild the rootfs and transfer the image into the SDCard:

~$ bitbake image-spi #for spi image
or
~$ bitbake image-full #for full featured yocto BSP.

Hardware Wiring Recommendation

This guide assume Adafruit 2.8" TFT shield v2 (based on ili9341 chip) is used. Please refer to Adafruit Website for more details. This guide assumes that the default pins are used - TFT_DC (Arduino #IO9) and TFT_CS (Arduino #IO10). ~~Fbtft driver do not work well with the GPIOs connected to the I2C expander.~~ ~~Please re-route TFT_DC (IO9) and TFT_CS (IO10) to Digital IO2 and IO3 as they connect directly to Quark SoC.~~

Setting-Up GPIO (Valid for Intel Galileo Gen1 board only)

Create a shell script to initialize the GPIO. Execute the script before loading FBTFT driver module. Please refer to Malinov's Website for Intel Galileo GPIO mapping details. I will provide the script to enable Gen2 GPIO later

#!/bin/sh

#GPIO42 is IO10_MUX
echo -n "42" > /sys/class/gpio/export
echo -n "out" > /sys/class/gpio/gpio42/direction
echo -n "1" > /sys/class/gpio/gpio7/value

#initialize CS pin and drive the pin low.
echo -n "16" > /sys/class/gpio/export
echo -n "out" > /sys/class/gpio/gpio16/direction
echo -n "0" > /sys/class/gpio/gpio16/value

#SPI1 pins

#IO11_MUX (SPI1_MOSI)

echo "43" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio43/direction
echo "0" > /sys/class/gpio/gpio43/value

#IO12_MUX (SPI1_MISO)

echo "54" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio54/direction
echo "0" > /sys/class/gpio/gpio54/value

#IO13_MUX (SPI1_SCK)

echo "55" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio55/direction
echo "0" > /sys/class/gpio/gpio55/value

#note: TFT_DC pin (GPIO19) and SPI1 will be initialized & owned by the fbtft driver

Loading the Kernel Module from Yocto Shell:

Execute the following shell commands in the shell to load fbtft driver:

~# modprobe fbtft_device custom name=fb_ili9341 buswidth=8 gpios=dc:19 width=240 height=320 busnum=1 bgr=1 speed=5000000
~# modprobe fb_ili9341

Verify that /dev/fb0 exists and execute "cat /dev/urandom > /dev/fb0" in the priviledged shell.
You should see random dots printed on the tft device.