u8g2-copy/sys/arm-linux

U8g2 for arm-linux has been modified to use c-periphery userspace library.

• Deprecated sysfs method is no longer used for GPIO thus increasing speed and stability, but you can still use sysfs for legacy kernels.
• GPIO, I2C and SPI can be closed and unallocated.
• Overall performance should be better.
• Run as non-root user.

Non-root access

If you want to access devices without root do the following (you can try udev rules instead if you wish):

• sudo groupadd u8g2
• sudo usermod -a -G u8g2 username (Use a non-root username)
• sudo nano /etc/rc.local

chown -R root:u8g2 /dev/gpiochip*
chmod -R ug+rw /dev/gpiochip*
chown -R root:u8g2 /dev/i2c*
chmod -R ug+rw /dev/i2c*
chown -R root:u8g2 /dev/spidev*
chmod -R ug+rw /dev/spidev*

• sudo reboot

Download U8g2 project

• cd ~/
• git clone --depth 1 https://github.com/olikraus/u8g2.git

Modify source as needed

• Change example (SPI 4 wire hardware for instance)
• nano ~/u8g2/sys/arm-linux/examples/c-examples/u8g2_4wire_hw_spi\u8g2_4wire_hw_spi.c
• Change the GPIO chip number (0 uses /dev/gpiochip0)
• #define GPIO_CHIP_NUM 0
• Change the SPI bus number (0x10 uses /dev/spidev1.0)
• #define SPI_BUS 0x10
• Change the DC and RESET as needed (NanoPi Duo here using tx1 and rx1)
• #define OLED_SPI_PIN_RES 199
• #define OLED_SPI_PIN_DC 198

Build source with GPIO character device

• cd ~/u8g2/sys/arm-linux
• make clean
• make CPPFLAGS=-DPERIPHERY_GPIO_CDEV_SUPPORT=1 CC=gcc CXX=g++

Build source with GPIO sysfs

• cd ~/u8g2/sys/arm-linux
• make clean
• make CC=gcc CXX=g++