OLD Bare Metal System Image

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This page will guide you through the steps to install a basic system image.

On this image you will have the ROS base system, the OpenMower installation, local configuration for your mower and some tools to help you work with the mower.

Prerequisites

In order to follow this guide, you will need the following:

  1. A Raspberry Pi 4 (4GB or more recommended, 2GB works with swap, see below)
  2. An SD card
  3. A soldered OpenMower mainboard

Installing the Base System

There is also a YouTube video explaining the steps in this section: https://youtu.be/_bImqD-pQSA?t=562

1. Flashing Ubuntu to SD Card

The first step is to install the base system. We're using Ubuntu 20.04 Server for the Raspberry Pi. This is, because this image gives us best support ROS Noetic.

Installing the base image is easy:

  1. Get the Raspberry Pi Imager software [1]
  2. Select the correct operating system: Other-general-purpose OS > Ubuntu > Ubuntu Server 20.04.4 LTS (RPI 3/4/400)
  3. Insert your SD card into your PC and select it in the Storage part of the software
  4. Click write and wait for the process to finish


Once you have successfully flashed your image, remove the SD for your PC and reinsert it again.

Then replace the /boot/config.txt file with the one provided here: [2]

This will enable all hardware serial ports on the Raspberry Pi.


Note:

You can theoretically configure networking in this step as well, but I'm not recommending it. This is, because the networking information file gets only copied once and if you have an error it won't work. We need an interactive terminal in the next step anyways.


Once you have done this step, you can eject the SD card and plug it into your Raspberry Pi 4.

2. Installing a WiFi Hot-Spot (optional, but recommended)

As soon as you have closed your mower, you won't have physical access to your Raspberry Pi anymore. If for some reason it's unable to connect to your WiFi (e.g. you have changed your password), you would need to open the case to get access to the SD card or Ethernet port on the Pi to regain access.

To prevent this, we're going to install a hot-spot software which helps you to connect to WiFi by opening a hot-spot each time the Pi cannot connect to a known WiFi connection.

Now is the best time to do this, because we have a serial terminal anyways and can mess with the network interfaces without shutting us out of the system!

3. Disable Boot Interrupt

The Raspberry Pi boot loader will interrupt the boot sequence if data is sent through the main serial port of the Raspberry Pi. Since we're connecting "nosiy" hardware to the port, this will always interrupt the boot sequence and we need to disable this feature. For this, we will connect to the Pi's serial terminal and boot it.

The easiest way of doing so is:

  1. Flash the SerialRedirect firmware into your Pico. Get it here: https://github.com/ClemensElflein/OpenMower/tree/main/Firmware/SerialRedirect/bin
  2. Provide your mainboard with power
  3. Plug your Pico into another computer. A virtual COM port should appear
  4. Connect to the COM port, then press enter to start the Raspberry Pi
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