Development
This is a step-by-step guide showing how to add and compile a new FBTFT driver in 30 minutes.
First check if flexfb can be used.
This guide can also be used to get the latest driver update, if a new image hasn't been released yet. Follow the guide and skip the example driver. If a new driver has been added, it must be added in the kernel config for it to be built (make menuconfig).
Boot with latest FBTFT image.
Expand root file system size.
sudo raspi-config
# expand_rootfs
sudo apt-get update
sudo apt-get -y install git libncurses5-dev
Samba can be used to aid development on the Pi.
sudo apt-get -y install samba samba-common-bin
sudo cp /etc/samba/smb.conf /etc/samba/smb.conf.org
sudo sed -i '/ Share Definitions /q' /etc/samba/smb.conf
cat <<EOF | sudo tee -a /etc/samba/smb.conf
[homes]
comment = Home Directories
browseable = no
read only = no
create mask = 0644
directory mask = 0755
valid users = %S
EOF
sudo service samba restart
sudo smbpasswd -a pi
Home directory for user pi will be available at \\xxx.xxx.xxx.xxx\pi
We don't need the complete git history (--depth 1). This will speed things up considerly.
cd
git clone --depth 1 git://github.com/raspberrypi/linux.git
fbtft source
cd ~/linux/drivers/video/
git clone https://github.com/notro/fbtft.git
# Let make/kbuild see the directory and config options.
echo "obj-y += fbtft/" >> Makefile
sed -i 's/endmenu/source "drivers\/video\/fbtft\/Kconfig"\n\nendmenu/' Kconfig
cp ~/extra/.config ~/linux/
cp ~/extra/Module.symvers ~/linux/
cd ~/linux
make prepare scripts
This shows how to add a new driver.
Add to ~/linux/drivers/video/fbtft/Kconfig
config FB_HELLO
tristate "Example FBTFT driver"
depends on FB_TFT
Add to ~/linux/drivers/video/fbtft/Makefile
obj-$(CONFIG_FB_HELLO) += hellofb.o
Add to static struct spi_board_info fbtft_device_spi_displays[] in file ~/linux/drivers/video/fbtft/fbtft_device.c
}, {
.modalias = "hellofb",
.max_speed_hz = 32000000,
.mode = SPI_MODE_0,
.platform_data = &(struct fbtft_platform_data) {
.gpios = (const struct fbtft_gpio []) {
{ "reset", 25 },
{},
},
}
Create ~/linux/drivers/video/fbtft/hellofb.c
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/gpio.h>
#include <linux/spi/spi.h>
#include <linux/delay.h>
#include "fbtft.h"
#define DRVNAME "hellofb"
#define WIDTH 128
#define HEIGHT 160
/* Module Parameter: debug (also available through sysfs) */
MODULE_PARM_DEBUG;
static int hellofb_init_display(struct fbtft_par *par)
{
fbtft_dev_dbg(DEBUG_INIT_DISPLAY, par->info->device, "%s()\n", __func__);
printk("Hello World");
return 0;
}
struct fbtft_display hellofb_display = {
.width = WIDTH,
.height = HEIGHT,
};
static int hellofb_probe(struct spi_device *spi)
{
struct fb_info *info;
struct fbtft_par *par;
int ret;
fbtft_dev_dbg(DEBUG_DRIVER_INIT_FUNCTIONS, &spi->dev, "%s()\n", __func__);
info = fbtft_framebuffer_alloc(&hellofb_display, &spi->dev);
if (!info)
return -ENOMEM;
par = info->par;
par->spi = spi;
fbtft_debug_init(par);
par->fbtftops.init_display = hellofb_init_display;
ret = fbtft_register_framebuffer(info);
if (ret < 0)
goto out_release;
return 0;
out_release:
fbtft_framebuffer_release(info);
return ret;
}
static int hellofb_remove(struct spi_device *spi)
{
struct fb_info *info = spi_get_drvdata(spi);
fbtft_dev_dbg(DEBUG_DRIVER_INIT_FUNCTIONS, &spi->dev, "%s()\n", __func__);
if (info) {
fbtft_unregister_framebuffer(info);
fbtft_framebuffer_release(info);
}
return 0;
}
static struct spi_driver hellofb_driver = {
.driver = {
.name = DRVNAME,
.owner = THIS_MODULE,
},
.probe = hellofb_probe,
.remove = hellofb_remove,
};
static int __init hellofb_init(void)
{
fbtft_pr_debug("\n\n"DRVNAME": %s()\n", __func__);
return spi_register_driver(&hellofb_driver);
}
static void __exit hellofb_exit(void)
{
fbtft_pr_debug(DRVNAME": %s()\n", __func__);
spi_unregister_driver(&hellofb_driver);
}
/* ------------------------------------------------------------------------- */
module_init(hellofb_init);
module_exit(hellofb_exit);
MODULE_DESCRIPTION("Example FBTFT driver");
MODULE_AUTHOR("Noralf Tronnes");
MODULE_LICENSE("GPL");
Start kernel configuration program
cd ~/linux
make menuconfig
Enable hellofb
Device Drivers ---> Graphics support ---> Support for small TFT LCD display modules --->
<M> Example FBTFT driver
make prepare
This can be run from any directory
make -C /lib/modules/$(uname -r)/build SUBDIRS=drivers/video/fbtft modules
sudo dmesg -C
sudo modprobe fbtft
sudo insmod ~/linux/drivers/video/fbtft/fbtft_device.ko name=hellofb
sudo insmod ~/linux/drivers/video/fbtft/hellofb.ko debug=3
dmesg
fbtft_device: SPI devices registered:
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: GPIOS used by 'hellofb':
fbtft_device: 'reset' = GPIO25
fbtft_device: SPI devices registered:
fbtft_device: spidev spi0.1 500kHz 8 bits mode=0x00
fbtft_device: hellofb spi0.0 32000kHz 8 bits mode=0x00
hellofb: hellofb_init()
hellofb spi0.0: hellofb_probe()
hellofb spi0.0: fbtft_request_gpios: 'reset' = GPIO25
hellofb spi0.0: hellofb_init_display()
hellofb spi0.0: Elapsed time for display update: 16.561898 ms (fps: 60, lines=160)
graphics fb1: hellofb frame buffer, 40 KiB video memory, 4 KiB buffer memory, fps=20, spi0.0 at 32 MHz
sudo rmmod hellofb fbtft_device
sudo cp /lib/modules/$(uname -r)/build/drivers/video/fbtft/fbtft_device.ko /lib/modules/$(uname -r)/kernel/drivers/video/fbtft/
sudo cp /lib/modules/$(uname -r)/build/drivers/video/fbtft/hellofb.ko /lib/modules/$(uname -r)/kernel/drivers/video/fbtft/
sudo depmod
sudo modprobe fbtft_device name=hellofb
sudo modprobe hellofb debug=3
When doing development and testing from a SSH session, it's nice to see the that kernel panic message before everything freezes.
Make file /etc/rsyslog.d/kern_pi.conf with contents:
kern.err pi
This will show kernel error messages and worse when user pi is logged in.
service rsyslog restart