Raspberry Pi

Various stuff with Raspberry Pi.

Setting up toolchain

Demos in this repository requires clang toolchain that targets your Raspberry Pi distribution. Following scripts will help you to compile clang on GNU/Linux desktop for targeting Raspberry Pi with Raspbian, Ubuntu, Arch Linux ARM or Alpine Linux distributions:

• setup.sh - sets up generic environment variables for specific distribution and Pi
• sysroot.py - unpacks raspbian or alarm packages in sysroot
• bootstrap.sh - compiles clang toolchain

First you need to set up environment variables by sourcing setup.sh file:

source setup.sh <distro> <pi_version>

Where distro is raspbian for Rasbian, ubuntu for Ubuntu, alarm for Arch Linux ARM or alpine for Alpine Linux. pi_version is which Raspberry Pi you want to target - pi1, pi2, pi3, pi3-64, pi4 or pi4-64. pi3-64 is available only for Arch Linux ARM and Alpine Linux. pi4 is tested only on Arch Linux ARM and Raspbian. pi4-64 is tested only on Arch Linux ARM.

This script will also set necessary environment variables for pkg-config to work - it will use only packages from sysroot folder, not from your host folder.

Remember to source it every time you want to use clang for compiling your code.

Next install basic packages (like C runtime) in sysroot with help of sysroot.py script. For example, for Rasbian use this:

./sysroot.py --distro raspbian --sysroot "${SYSROOT}" libc6-dev libstdc++-6-dev

For Ubuntu:

./sysroot.py --distro ubuntu --sysroot "${SYSROOT}" libc6-dev libstdc++-6-dev

For Arch Linux ARM:

./sysroot.py --distro alarm --sysroot "${SYSROOT}" --target "${TARGET}" gcc glibc

For Alpine Linux:

./sysroot.py --distro alpine --sysroot ${SYSROOT} --target ${TARGET} g++ musl-dev

Make sure you have dpkg-deb executable available if you are targeting rasbian or ubuntu (on Arch install it from AUR).

This script will create sysroot folder with development header files and libraries targeting your choice of distribution and target architecutre. You'll need to repeat this process in case you run setup.sh again with different distro/pi_version arguments. Each sysroot is setup in separate folder. Package resolving is very simplified and may fail on complex dependencies, also it DOES NOT verify integrity of downloaded packages, be careful!

Now execute bootstrap.sh script to compile clang:

./bootstrap.sh

This script requires gcc based buildsystem and cmake on your host machine. It will create toolchain folder where it will install clang compiler and lld linker. Clang will be built for ARM and AArch64 targets. To use it in your code use ${CC} and ${CXX} variables for path to C and C++ compilers.

Demos

Currently available demos:

• gles2_bcm - how to use GLES2 for Broadcom's propriatery OpenGL driver
• gles2_drm - how to use GLES2 for open-source vc4 OpenGL driver with libdrm & mesa
• gles2 - how to use GLES2 with any of two OpenGL drivers
• gl2_drm - how to use GL2 for open-source vc4 OpenGL driver with libdrm & mesa

Useful info about Raspberry Pi

To check which Pi you have, check contents of /proc/device-tree/model file. Alternatively check Revision field in /proc/cpuinfo file and match to this table.

To get temperature of Pi, check /sys/class/thermal/thermal_zone0/temp (divide by 1000 to get °C).

/boot/config.txt stuff

gpu_mem=128 - how much memoy to allocate for GPU in MiB

dtoverlay=vc4-fkms-v3d - enables open-source OpenGL driver

hdmi_force_hotplug=1 - HDMI always enabled

hdmi_group=2 - sets HDMI mode

hdmi_mode=82 - forces 1920x1080@60 HDMI mode

disable_overscan=0 - disables HDMI overscan