These steps will help you through the installation of preempt-rt on the Raspberry Pi 4. The kernel that is used is the 4.19.86 linux kernel.
- It contains additional support as an option to use W5500 Ethernet network driver for users who need extra ethernet port on raspberry pi.
- You can find out much more simplified method using pre-built kernel on the link
- Raspberry Pi 4
- 16gb Micro-SD card + reader
- Computer with Ubuntu
- (Option) WIZnet W5500 Ethernet chip with SPI interface
Create a new raspbian image on the micro-SDcard with the Pi imager. Use the file on the link below.
2020-02-13-raspbian-buster.zip
- Create directories on the host computer
host@ubuntu:~$ mkdir rpi-kernel
host@ubuntu:~$ cd rpi-kernel
host@ubuntu:~/rpi-kernel$ mkdir rt-kernel- Start by pulling the linux repository
host@ubuntu:~/rpi-kernel$ git clone -b rpi-4.19.y-rt https://github.com/raspberrypi/linux.git
host@ubuntu:~/rpi-kernel$ git clone https://github.com/raspberrypi/tools.git- Environment variable setting
host@ubuntu:~/rpi-kernel$ export ARCH=arm
host@ubuntu:~/rpi-kernel$ export CROSS_COMPILE=~/rpi-kernel/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-
host@ubuntu:~/rpi-kernel$ export INSTALL_MOD_PATH=~/rpi-kernel/rt-kernel
host@ubuntu:~/rpi-kernel$ export INSTALL_DTBS_PATH=~/rpi-kernel/rt-kernel- Setting for Raspberry pi 4
host@ubuntu:~/rpi-kernel$ export KERNEL=kernel7l
host@ubuntu:~/rpi-kernel$ cd linux/
host@ubuntu:~/rpi-kernel/linux$ make bcm2711_defconfig- Configurate Kernel Compile options
host@ubuntu:~/rpi-kernel/linux$ sudo apt-get install libncurses-dev libssl-dev flex bison
host@ubuntu:~/rpi-kernel/linux$ make menuconfig- Edit the following variables:
[Kernel hacking] → [Debug preemptible kernel] Off
(Option) [Device Drivers] → [Network device support] → [Ethernet driver support] → [WIZnet W5100 Ethernet support], [WIZnetW5100/W5200/W5500 Ethernet support for SPI mode] On
- Build the linux kernel (This can take some time, so get coffee or tea...)
host@ubuntu:~/rpi-kernel/linux$ make -j4 zImage modules dtbs
host@ubuntu:~/rpi-kernel/linux$ make –j4 modules_install dtbs_install- Create .img Kernel file
host@ubuntu:~/rpi-kernel/linux$ mkdir $INSTALL_MOD_PATH/boot
host@ubuntu:~/rpi-kernel/linux$ ./scripts/mkknlimg ./arch/arm/boot/zImage $INSTALL_MOD_PATH/boot/$KERNEL.img- Replace the Kernel to Raspberry Pi
host@ubuntu:~/rpi-kernel/linux$ cd $INSTALL_MOD_PATH
host@ubuntu:~/rpi-kernel/rt-kernel$ tar czf ../rt-kernel.tgz *
host@ubuntu:~/rpi-kernel/rt-kernel$ cd ..
host@ubuntu:~/rpi-kernel$ scp rt-kernel.tgz pi@<raspberry pi IP address>:/tmp- Inside the raspberry pi, unpack the .tgz and copy it
pi@raspberrypi:~$ cd /tmp
pi@raspberrypi:/tmp$ tar xzf rt-kernel.tgz
pi@raspberrypi:/tmp$ cd boot
pi@raspberrypi:/tmp/boot$ sudo cp -rd * /boot/
pi@raspberrypi:/tmp/boot$ cd ../lib
pi@raspberrypi:/tmp/lib$ sudo cp -rd * /lib/
pi@raspberrypi:/tmp/lib$ cd ../overlays
pi@raspberrypi:/tmp/overlays$ sudo cp -d * /boot/overlays
pi@raspberrypi:/tmp/overlays$ cd ..
pi@raspberrypi:/tmp$ sudo cp -d bcm* /boot/- Edit the boot configutarion
pi@raspberrypi:/tmp$ sudo nano /boot/config.txtAdd in the beginning:
kernel=kernel7l.img
(Option) Type in the last line:
dtoverlay=w5500
- Reboot and check the patched kernel
pi@raspberrypi:/tmp$ sudo reboot
pi@raspberrypi:~$ uname -r