/pi_hw_interface

Primary LanguageC++

Pi Hw Interface

A Ros2 hardware interface that works with Raspi GPIO through libgpiod interface

Requires: gpiod, libgpiod

In order to run the executable, the system must have a set of Udev rules along with a new user group created. Use the following steps to configure the Udev rule and accompanying groups.

  1. Configure the UDEV rule

    Note: run this command as root (use sudo su in order to get a superuser prompt)

    echo '# udev rules for gpio port access through libgpiod
SUBSYSTEM=="gpio", KERNEL=="gpiochip[0-4]", GROUP="gpiod", MODE="0660"' > /etc/udev/rules.d/60-gpiod.rules

  2. Create the gpiod user group

    sudo groupadd gpiod

  3. Add the current user to the gpiod group

    sudo usermod -G gpiod <user>

This node also relies on an updated linux kernel for the Raspi for full functionality, including handling for the pull up and pull down resistors on the GPIO pins. A flag can be set to disable this on systems that cannot be upgraded. For full functionality, the current kernel used is based on 5.11.

The process to force the updated kernel and libgpiod-dev were via enabling the PPA for ubuntu 21.04 otherwise known as Hirsute Hippo. From there, the kernel and libgpiod were upgraded after using the following command to make sure apt would pull the correct version

sudo apt-cache policy linux-image-raspi libgpiod-dev

The linux image upgrades the kernel and libgpiod-dev upgrades libgpiod for this software. After the install process finishes the node can be re-built to enable the new features.

The I2C portion of this library depends on https://github.com/amaork/libi2c as well as libi2c-dev installed on the system








This is documentation on how to build a pi kernel for raspbian and is not relevant for ubuntu 20.04 Instead pull the kernel from a newer version of ubuntu server for raspberry pi

Take the following steps to build and upgrade the kernel from this site: https://www.raspberrypi.org/documentation/linux/kernel/building.md

Followed Steps to build and install the kernel:

  1. Clone the kernel repo and check out the desired tag

    It is recommended to use the release tagged versions rather than just the master branch.

    git clone --depth=1 --branch raspberrypi-kernel_1.20210430-1 https://github.com/raspberrypi/linux

  2. make the config

    For ras pi 3: make bcmrpi3_defconfig

    For ras pi 4: make bcm2711_defconfig

  3. Make the kernel and its dependents

    make -j4 Image modules dtbs

    Note: the -j4 allows all cpus on the pi to be used to compile, which speeds up the process significantly

  4. Install the kernel