os-course-labs: A C repository from romanjoe

Set up Docker

NOTE: Everything you do inside container stays in CONTAINER, not an IMAGE. Changes have to be applied to Dockerfile to persist

On Mac via homebrew

https://medium.com/@yutafujii_59175/a-complete-one-by-one-guide-to-install-docker-on-your-mac-os-using-homebrew-e818eb4cfc3

Commands to execute before start

Start docker-daemon process:

docker-machine start default
docker-machine env
eval $(docker-machine env)

On Windows

Using guide provided by Docker https://docs.docker.com/docker-for-windows/install/

On Linux

Most likely docker is present in your disros packet manager. For example refer to guide for Ubuntu 18.04

https://phoenixnap.com/kb/how-to-install-docker-on-ubuntu-18-04

Start using Docker

docker login

Get Docker image with Raspberry Pi cross compilation environment.

docker image pull romanjoe/rpi-cc:latest

This may take some time, as image is aroung 3GB.

rpi-cc Docker image contents

Ubuntu - base image

arm-linux-gnueabihf- - toolchain for cross compilation from official raspberry pi tools repository, compatible with Raspbian Buster

build utils - set of packages needed to build kernel

linux kernel - source code for linux kernel version 4.19.y used on raspberry pi board and installed in Raspbian Buster Lite by the time of creation of this image

compiled kernel - raspberry pi kernel to support cross compilation of modules

Useful Docker commands

Start Docker container in interactive mode. Container will be started and /bin/bash program executed. You are logged in as root user inside container.

docker run -ti %image_name:tag% /bin/bash

Additionally mount some user folders to container before run. In this example contents of host directory /Users/rnok/ucu/os-course-labs/demo will be mounted to contaner at /home/workdir. /home/workdir is set to default work directory in image configuration. You also will be logged in as root. Issue ls -l command to see contents of demo folder present in container space.

docker run -v /Users/rnok/ucu/os-course-labs/demo:/home/workdir -it romanjoe/rpi-cc /bin/bash
ls -l

You can check images preset in your system using this command.

docker image ls

Or list of all cotainers, including stopped.

docker container ls -a

The most frequent command that will be used in scope of this course presented below. Here current working directory on host evaluated by pwd command will be mounted to /home/workdir of container, then make command will be executed inside container in folder /home/workdir/demo, where project Makefile is located. Results of compilation will be stored in pwd and container will be killed after execution.

docker run -v `pwd`:/home/workdir -it romanjoe/rpi-cc make

docker run -v `pwd`:/home/workdir -it romanjoe/rpi-cc make clean

This command is encapsulated in run script in demo dir.

Getting Raspberry Pi ready

Hardware required

Raspberry Pi model B+
Micro SD card 8gb or more
Power source capable to provide 2A current
USB A to USB micro B cable
Externally connected LED or other indication device.

Software

Download Raspbian OS Buster Lite from 2019-09-30 from raspbian downloads repo
Download Balena Etcher software from Balena
Use Balena Etcher to flash Raspbian Buster Lite to SD card.

Do not eject SD card yet.

Set up wireless connection

Enble ssh service on Raspberry Pi On Linux and Mac

 touch /Volumes/boot/ssh

On Windows

 Create file in Notepad with name ssh, push space key to make changes to is and save file to /boot folder without any extension.

Go to boot folder of SD card and create file called wpa_supplicant.conf with following content.

 country=US
 ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
 update_config=1

 network={
     ssid="NETWORK-NAME"
     psk="NETWORK-PASSWORD"
 }

Replace NETWORK-NAME and NETWORK-PASSWORD with your local WI-FI network credentials. If your network requires sophisticated authentification method to login - the easiest way to overcome is to use you phone in Hotspot mode.

Eject SD card from PC and install to Raspberry Pi, wait around 15-20 sec
Switch your laptop to same WI-FI network you put into wpa_supplicant.conf
Establish ssh connections to your board.

On Linux and Mac:
```
 ssh-keygen -R raspberrypi.local
 ssh pi@raspberrypi.local
```
Here we create new file raspberrypi.local of knows hosts type. And then logging in to it with user name pi. On password request type raspberry - this is defalt password of pi user.

On Windows

Popular program PuTTY can be used to access. Open program and type raspberrypi.local at host name field. Leave other fiels as it is. Warning message would appear at first time connection - add this host to list of knows.

Get updates and linux kernel headers

Suppose you are at raspberry pi terminal.

 sudo apt-get update -y
 sudo apt-get upgrade -y

Install linux kernel headers to Raspberry Pi
```
 sudo apt-get install raspberrypi-kernel-headers
 sudo apt-get install -y build-essential bc bison flex libssl-dev
```
Check folder /libs/modules/4.19.85-v7+/build - it should contain linux kernel folders.

Apply patch for fix wrong fixdep bin format.

 cd /libs/modules/4.19.85-v7+/build

 sudo wget https://raw.githubusercontent.com/romanjoe/os-course-labs/master/patches/headers-debian-byteshift.patch -O - | sudo patch -p1

Recompile executables in scripts folder.
```
 make scripts
```
Copy source code of examples from this repository demo, gpio to Raspberry Pi.
```
 scp -r demo pi@raspberry.local:/home/pi/native
```
/home/pi/native folder will be used for compilation of board. /home/pi/cross folder will be used to host cross compiled objects.

Compile demo content.

 cd /home/pi/native/demo

 make CROSS=0

if you see no errors on compilation and new files appeared in folder - you are you done with setup successfully.