Single board computer projects

Raspberry Pi tips and tricks

last updated: 2021-10-18

Create µSD-card

!New! The Raspberry Pi Imager

https://www.raspberrypi.org/blog/raspberry-pi-imager-imaging-utility/

The Raspberry Pi Imager is open source (https://github.com/raspberrypi/rpi-imager) and facilitates the creation of the µSD card. Install it on Linux with:

    sudo apt install rpi-imager

It is quite self explaining. Even Libreelec (Kodi) or octopi can be installed immediately.

But the best is the magic key Ctrl + Shift + x.

In the advanced menu we can enable ssh, set the raspi and Wifi password and the locales. (don't forget to scroll!).

Get SSH and WIFI working before first boot

This is only needed if you don't use the Raspi imager!

As of the November 2016 release, Raspbian (now Raspi OS) has the SSH server disabled by default. It can be enabled by placing an empty file named ssh, without any extension, onto the boot partition of the SD card.

For this insert the newly written SD-card into your PC and mount the boot partition (FAT32). Now create an empty text-file with the name ssh (no extension).

Next create a text-file with the name wpa-supplicant.conf and add the following text to the file (the country line is optional):

country=LU
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
network={
  ssid="mySSID"
  psk="myPassword"
}

As the password is stored in clear text it is a better idea to use the tool wpa_passphrase to generate a pre-encrypted 32 byte hexadecimal number.

    wpa_passphrase mySSID myPassword

creates the following Output:

network={
        ssid="mySSID"
        #psk="myPassword"
        psk=91fa3d0528b7a0f57cf69f62d2ded92f26479f5948e35c3309961bade47459c4
}

Delete the line with # and copy the text to your wpa-supplicant.conf.

For more info on login with ssh look further down.

Raspbian with Desktop

The new Raspbian with desktop is easy to use. The filesystem of your SD-card is automatically expanded during the first boot. The system starts without login or password request.

With HDMI Monitor, USB mouse and USB keyboard you have a full desktop PC and it is simple to configure your Raspi by desktop means.

Configuring Raspi by desktop means

To enable your Wifi, click the icon right to the bluetooth sign. Choose your hotspot (SSID) and type the pre shared key (this settings will be automatically written to your wpa_supplicant file).

Click the start menu (a raspberry :)) and then: Menu ⇨ Preferences ⇨ Raspberry Pi Configuration.

To set your keyboard , time zone an localisation settings click on Localisation:

Configuring localisation

To enable interfaces (1-wire, I2C, serial) click on Interfaces:

Configuring localisation

Here it is also possible to enable VNC to use your Raspi remotely.

Use Raspi remotely with VNC

We enable VNC in Menu ⇨ Preferences ⇨ Raspberry Pi Configuration ⇨ Interfaces From now on, VNC server will start automatically at boot. If we have no static IP address, get your Raspi's private IP address by clicking the VNC icon on your menu bar.

Download VNC Viewer on https://www.realvnc.com/raspberrypi and run it on your device. Now you can take control of your Raspi, as if you were sitting in front of it.

If you want to connect over the internet, you will need to configure your firewall to enable VNC, and port forward your router to your Raspi's IP address.

Add a static IP address

It is simpler to know Raspi's IP address, so we set it static. We can do this in the GUI, on the command line or even before inserting the SD card in the Raspi if we use Linux or a Windows with software to mount the ext4 file system.

Ethernet and WiFi have to get both different IP addresses if used together (also the MAC addresses are different!)!

GUI

Right click on the WiFi Icon in the bottom right corner. We get a menu item called Wireless & Wired Network Settings. Enter the IP address and the default Gateway (Router). As most router also work as DNS server, add the same IP for DNS Servers.

/savit/www.weigu/tutorials/sensors2bus/05buses/png/raspiguifixip_350.png

The infos on the static IP address are saved in a file in the /etc folder called /dhcpcd.conf.

Command line

Call the midnight commander sudo mc and open the file dhcpcd.conf in the /etc folder. Press F4 to open the nano text editor and uncomment the following lines in /etc/dhcpcd.conf. Change the IP addresses to your needs (alternatively use sudo nano /etc/dhcpcd.conf).

    # Custom static IP address for eth0.
    interface eth0
    static ip_address=192.168.1.67
    static routers=192.168.1.1
    static domain_name_servers=192.168.1.1

    # Custom static IP address for wlan0.
    interface wlan0
    static ip_address=192.168.1.69
    static routers=192.168.1.1
    static domain_name_servers=192.168.1.1

Save the file with Ctrl-O, exit with Ctrl-X , exit mc with F10 and reboot (sudo reboot). Now we can log in with the new IP.

If we can mount the SD card on our PC, we can also add the infos to /etc/dhcpcd.conf before powering up the Raspi.

Update and upgrade

To get the latest versions of all programs, open the terminal window (4th icon in menu bar) and type:

    sudo apt update
    sudo apt upgrade
    sudo apt dist-upgrade

It is a good idea to install the terminal file manager "midnight commander (mc) to search and edit files as root in terminal (sudo mc) and htop to look at processes.

    sudo apt install mc htop

Log in with SSH

As of the November 2016 release, Raspbian has the SSH server disabled by default. It can be enabled by placing an empty file named ssh, without any extension, onto the boot partition of the SD card. For more information look at this link.

If you don't know the IP address of the Raspi, use nmap. On your PC type:

    sudo nmap -sP 192.168.1.*

If nmap is not installed:

    sudo apt install nmap

Look for the IP address of your Raspi (ex.: 192.168.1.125) and log in with ssh (putty on windows):

    sudo ssh pi@192.168.1.125

Python 3

Python3 is already installed. Use idle3 by clicking Menu ⇨ Programming ⇨ Python 3 (IDLE). CTRL+N opens a new file to type your code. Execute the code with F5.

Setting up the webserver Lighttpd with cgi

Lighttpd is an efficienct high performance webserver. It has a small memory footprint and an effective management of the cpu-load compared to other web-servers.

    sudo apt update
    sudo apt upgrade
    sudo apt install lighttpd

Test if the webserver is running by typing the ip address of your Raspi in the url field of your browser.

The html files are in in /var/www/html.

Make the cgi-bin directory /var/www/cgi-bin. After this we will edit the lighttpd config file.

    sudo mkdir /var/www/cgi-bin
    sudo nano /etc/lighttpd/lighttpd.conf

Add the following lines to the config file:

    server.modules += ( "mod_cgi" )
    alias.url += ( "/cgi-bin/" => "/var/www/cgi-bin/" )
    $HTTP["url"] =~ "/cgi-bin/" {
            cgi.assign = (
                  ".py" => "/usr/bin/python",
             )
    }

We have to change the owner of the web directories to pi and reload the server:

    sudo chown -R pi.pi /var/www
    sudo service lighttpd force-reload

Now we can create our cgi python script (ex.: my1cgi.py). It has to be executable, so we change this with chmod:

    chmod 711 /var/www/cgi-bin/my1cgi.py

If we need php:

    sudo apt-get install php5-common php5-cgi php5

Don't change the order of the packages to install or Apache will be installed. If we need a database:

    sudo apt-get install mysql-server php5-mysql

Adding a cron job at restart

If you want to start a python script automatically at reboot, add the following line to your /etc/crontab file.

    @reboot pi python3 /home/myname/myscript.py >> /home/myname/myscript_log.txt 2>&1

The output of the python script is redirected to a text-file, for debugging. To log the cron jobs uncomment cron in the file /etc/rsyslog.conf. You will find the log file in /var/log/cron.log. Here is a helpfull link if you have trouble with your cron job.

Install (newest) Arduino IDE and Teensyloader on Raspi

Run these commands in terminal to update your Raspi and to make a folder named "arduino" in your home directory:

    sudo apt update
    sudo apt upgrade
    sudo apt dist-upgrade
    mkdir ~/arduino

Download the newest Arduino version (Linux ARM version!!) on [arduino.cc](

    cd ~/arduino/arduino-1.8.4
    sudo ./install.sh

Download the newest Teensyduino version (ARM version!!) on pjrc.com. Make the file executable and run it. Choose the right directory with your arduino (ex. ~/arduino/arduino-1.8.4).

To set up the udev rules (so you have not to be root to use your Teensy), use this file: udev rules and copy it to /etc/udev/rules.d. Restart your Raspi ()sudo reboot).

Prevent Raspi dropping WiFi

My Pi became randomly inaccessible over WiFi. In /var/log/syslog I found:
{TIMESTAMP} raspberrypi dhcpcd[{PID}]: wlan0: carrier lost
It turned out the problem was that the Pi WiFi controller has power_save on by default.

Command to read the current power saving mode (Stretch):

    sudo iw wlan0 get power_save

Command to power_save off:

    sudo iw wlan0 set power_save off

To make this permanent add the following line to /etc/rc.local:

/sbin/iw dev wlan0 set power_save off

Raspbian lite

If you have an HDMI Monitor, a USB mouse and USB keyboard it is possible to login without network connection and configure your Raspi. If not, use a wired network connection; get the IP adress with nmap and connect with ssh to your Raspi (see "Log in with SSH"). After setting up Wifi (see "Set up Wifi") you may disconnect the wired connection.

The login is pi, the password is raspberry (with a german keyboard the password is raspberrz :)).

Raspi-config

Raspbian has a cool tool to change settings. Type

    sudo raspi-config

Expand the filesystem

Click on "1 Expand Filesystem" to use later all the space from your SD-card.

Change the keyboard layout and the timezone

When you do not use an english keyboard use sudo raspi-config and click on "4 Internationalisation Options". With "I3" you can adjust the keyboard layout. It is a good idea to use "I2" to chose the right time zone. The locale per default is 'en_GB.UTF-8 UTF-8'. If you want to change your locale you may do this under "I1".

Enable I2C, Serial and 1-Wire

Click on "Advanced Options" to get access to "A7", "A8" and "AA".

Hostname and password

In a network with more than one Raspi it is good to change the hostname ("Advanced Options", "A1"). The password can be changed under "Change User Password". To update raspi-config look under "Advanced Options", last point "A0".

If all this is done, it is a good time to reboot (Bob: "reboot tut gut!):

    sudo reboot

Set up Wifi

The new Raspi3 has Wifi on board, so we need to activate it to gain wireless network access.

    cd /etc/wpa_suplicant
    sudo nano wpa_supplicant.conf

Add the following lines with the ssid of your access point and your password to the file:

    network={
        ssid="mySSID"
        psk="myPassword"
    }

Save with CTRL+O and exit with CTRL+X.

As the password is stored in clear text it is a better idea to use the tool wpa_passphrase to generate a pre-encrypted 32 byte hexadecimal number.

    wpa_passphrase mySSID myPassword

creates the following Output:

network={
        ssid="mySSID"
        #psk="myPassword"
        psk=91fa3d0528b7a0f57cf69f62d2ded92f26479f5948e35c3309961bade47459c4
}

Delete the line with # and copy the text to your wpa-supplicant.conf.

Log in with SSH

Now it's time to find the IP address of the Raspi. On your PC type:

    sudo nmap -sP 192.168.1.*

If nmap is not installed:

    sudo apt install nmap

Look for the IP address of your Raspi (ex.: 192.168.1.125) and log in with ssh (putty on windows):

    sudo ssh pi@192.168.1.125

Update and upgrade

Get the latest versions of all programs:

    sudo apt update
    sudo apt upgrade
    sudo apt dist-upgrade

Midnight commander

A really cool program

can very easily be used to browse and edit your Raspi files. Install and launch it with:

    sudo apt install mc
    sudo mc

Static IP address

To get a static IP adress is very easy in Jessie. Use the editor nano to append the following to the file /etc/dhcpcd.conf.

    # Custom static IP address for eth0.
    interface eth0
    static ip_address=192.168.1.67
    static routers=192.168.1.1
    static domain_name_servers=192.168.1.1 8.8.8.8

    # Custom static IP address for wlan0.
    interface wlan0
    static ip_address=192.168.1.69
    static routers=192.168.1.1
    static domain_name_servers=192.168.1.1 8.8.8.8

Use sudo mc with F4 to edit (2 for nano) or

    cd /etc
    sudo nano dhcpcd.conf

Save with CTRL+O and exit with CTRL+X.

Python 3

    sudo apt install python3, rpi.gpio

Adding a cron job at restart

If you want to start a python script automatically at reboot, add the following line to your /etc/crontab file.

    @reboot pi python3 /home/myname/myscript.py >> /home/myname/myscript_log.txt 2>&1

Synchronizing files with rsync

To synchronize two folder over ssh with password, use rsync (!source no /, target with /):

    rsync -avz -e "ssh -p port" /folder1/myfolder username@www.site.lu:/folder1/

Use Adafruit PITFT

This is for different TFT-displays from Adafruit (e.g. 3.5" 480x320). The helper script does all the work:

    cd ~
    wget https://raw.githubusercontent.com/adafruit/Adafruit-PiTFT-Helper/master/adafruit-pitft-helper2.sh
    chmod +x adafruit-pitft-helper2.sh
   sudo ./adafruit-pitft-helper2.sh

I had to chose 270 degrees (landscape) for the display to be oriented the right way.Say NO to "Would you like the console to appear on the PiTFT display?" and then YES to "Would you like the HDMI display to mirror to the PiTFT display?".

To calibrate the screen manually:

    sudo TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/dev/input/touchscreen ts_calibrate

Next you can run the following command which will let you draw-test the touch screen. Go back and re-calibrate if you feel the screen isn't precise enough!:

    sudo TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/dev/input/touchscreen ts_test

Using exclusively 5GHz WLAN on new Raspi 3 B+

Using my Raspi as Bluetooth extender for my radio (Bluehemian Raspberry, c't 11/2018 page 132) didn't work. The play back was stuttering. Apparently it is not possible to use Bluetooth + WLAN (2,4GHz) on Raspi3 at the same time. An external USB WLAN or Bluetooth Stick may help. Instead I used a new Raspi3 B+ with 5GHz WLAN. To force the 5GHz WLAN I had to add a line (freq_list) to my wpa_supplicant.conf file in /etc/wpa_supplicant:

    network={
        freq_list=5180 5200 5220 5240 5260 5280 5300 5320
        ssid="..."
        psk="..."
    }

Mounting a NAS folder on Raspi (NFS)

First I had to enable NFS on my Synology NAS. This is done by checking the boxes Enable NFS and Enable NFSv4 support in Control Panel - File Services. Now we have to enable NFS for our shared folder (Control Panel - Shared Folder) by clicking on Editand creating an NFS Permission. If you want all hosts on the home network to be able to access the shared folder you can use a wildcard (*) for the Hostname or IP field. The mount path (/volume1/music) is displayed on the bottom left of the screen. Don't forget to grant your users permissions to the shared folder.

To mount the shared folder via NFS install nfs-common:

    sudo apt install nfs-common

The showmount command helps query the NFS Server (IP address from NAS):

    showmount -e 192.168.1.xxx

You should see an output like /volume1/music *.

To mount the shared folder:

    sudo mount 192.168.1.xxx:/volume1/music /home/pi/Music

I had problems mounting my NAS folder with fstab on the Raspi. Finally I used rc.local (/etc) to do this. The following code had to be added before the exit 0 line:

    sleep 30
    mount 192.168.1.xxx:/volume1/music /home/pi/Music

Prevent Raspi dropping WiFi

Command to read the current power saving mode (Stretch):

    sudo iw wlan0 get power_save

Command to power_save off:

    sudo iw wlan0 set power_save off

To make this permanent add the following line to /etc/rc.local (before the exit 0!):

/sbin/iw dev wlan0 set power_save off

Pi shutdown

I added a bush-button (Pin 40 (GPIO21) to Ground) to my pitoucon. When the button is pressed for less than 3 seconds, my Pi reboots. If pressed for more than 3 seconds it shuts down.

The code is on github.com/gilyes/pi-shutdown. Pay attention, because the code uses the pin numbering (board) and not the GPIO numbering. If you use pin 5 (GPIO3) and it is pressed while shut down, the Pi restarts. This is not possible with pin 40.

If RPi lib is not installed, do this with:

    sudo apt install python3-rpi.gpio

I added the following line to /etc/rc.local (before the exit 0!):

    python3 /home/pi/pishutdown.py &

Hotttt!

The new Raspi4 gets quite hot. Better use a fan (not to big so the surrounding components are not an obstacle). To control the temperature and test if it gets too hot (what reduces the clock frequency of 1500 MHz) start this line in a second terminal:

    while true; do vcgencmd measure_clock arm; vcgencmd measure_temp; sleep 2; done&

Now let your Raspi work (idle the clock is only 600 MHz).

Spoofing the MAC address

Spoofing the MAC address can be necessary to preserve your privacy or to if you want to use a new Raspberry Pi as a replacement for an older one in a net.

Add the following to the line in /boot/cmdline.txt (at the end):

    smsc95xx.macaddr=xx:xx:xx:xx:xx:xx

and reboot.

Interesting Links

https://www.raspberrypi.org/blog/raspberry-pi-imager-imaging-utility/

Single board computer projects

Raspberry Pi tips and tricks

Quick links

Create µSD-card

Get SSH and WIFI working before first boot

Raspbian with Desktop

Configuring Raspi by desktop means

Use Raspi remotely with VNC

Add a static IP address

GUI

Command line

Update and upgrade

Log in with SSH

Python 3

Setting up the webserver Lighttpd with cgi

Adding a cron job at restart

Install (newest) Arduino IDE and Teensyloader on Raspi

Prevent Raspi dropping WiFi

Raspbian lite

Raspi-config

Expand the filesystem

Change the keyboard layout and the timezone

Enable I2C, Serial and 1-Wire

Hostname and password

Set up Wifi

Log in with SSH

Update and upgrade

Midnight commander

Static IP address

Python 3

Adding a cron job at restart

Synchronizing files with rsync

Use Adafruit PITFT

Using exclusively 5GHz WLAN on new Raspi 3 B+

Mounting a NAS folder on Raspi (NFS)

Prevent Raspi dropping WiFi

Pi shutdown

Hotttt!

Spoofing the MAC address

Interesting Links