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Raspberry Pi OS

Install Raspberry Pi OS​

The easiest way to install Raspberry Pi OS is to use the latest version of the Raspberry Pi Imager.

  1. Check which version of Raspberry Pi OS your Raspberry Pi is compatible with.
  2. If compatible, then install Raspberry Pi OS 64 bit no desktop to maximize memory for the Altair emulator build process.
  3. Learn how to use the Raspberry Pi Imager.
  4. Select the Raspberry Pi Imager Settings icon to configure the operating system installation, wifi settings and more.

Connect to your Raspberry Pi​

  1. From your desktop computer, start an SSH session to your Raspberry Pi.

  2. From the SSH session, run the following command to install the required packages

    sudo apt-get install -y libuv1-dev cmake build-essential gdb curl libcurl4-openssl-dev libssl-dev uuid-dev ca-certificates git libi2c-dev libgpiod-dev gpiod

Raspberry Pi Sense HAT support​

If you are building the Altair project on a Raspberry Pi with a Raspberry Pi PI Sense HAT then you need to enable the I2C bus.

From the command prompt, run the following command to enable I2C support for the Pi Sense HAT.

sudo raspi-config nonint do_i2c 0

Installing libgpiod v2.x on Debian/Ubuntu​

The Altair Emulator requires libgpiod v2.x to interface with GPIO pins and successfully build the project.

Verify if you have libgpiod v1.x or v2.x installed. This guide helps you install libgpiod v2.x from source, which is required for projects using the v2.x API.

Problem this Solves​

This fixes compiler errors when building projects that use libgpiod v2.x API functions:

warning: implicit declaration of function 'gpiod_request_config_new'
warning: implicit declaration of function 'gpiod_line_config_new' 
error: variable 'value' has initializer but incomplete type
error: 'GPIOD_LINE_VALUE_ACTIVE' undeclared
error: 'GPIOD_LINE_VALUE_INACTIVE' undeclared

These errors occur because the project code uses libgpiod v2.x API, but the system has libgpiod v1.x installed (common on Debian 12/Ubuntu 22.04).

Version Verification​

If you're unsure which version is installed, run these commands:

# Primary method - pkg-config
pkg-config --modversion libgpiod

# Check linked libraries in your system
ldconfig -p | grep gpiod

# Check installed packages
dpkg -l | grep libgpiod

# Check header files (v1 vs v2 have different structures)
find /usr/include /usr/local/include -name "gpiod.h" 2>/dev/null

# Check library file directly
strings /usr/local/lib/libgpiod.so.2 2>/dev/null | grep -i version

Prerequisites​

Install required build dependencies:

sudo apt update
sudo apt install -y build-essential cmake pkg-config autotools-dev autoconf libtool git autoconf-archive

Installation Steps​

1. Remove existing libgpiod v1.x (if installed)​

sudo apt remove libgpiod2 libgpiod-dev

2. Download and build libgpiod v2.x​

# Create temporary build directory
cd /tmp
wget https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/snapshot/libgpiod-2.1.tar.gz
tar -xzf libgpiod-2.1.tar.gz
cd libgpiod-2.1

# Configure and build
./autogen.sh --enable-tools --enable-bindings-cxx --prefix=/usr/local
make -j$(nproc)
sudo make install

3. Update library path​

# Add to library path
echo '/usr/local/lib' | sudo tee /etc/ld.so.conf.d/libgpiod.conf
sudo ldconfig

4. Verify installation​

pkg-config --modversion libgpiod
# Should output: 2.1.0 (or similar v2.x version)

# Verify library location
ldconfig -p | grep gpiod