Build Instructions

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• 1

  Parts and Materials

  The following parts and materials are required (as detailed in the Components section)

  • Raspberry Pi Zero W with Raspbian Jessie Lite installed (this version is important if you want to make the file system read-only; see the optional last step)
  • 3D prints of the files in the "3D Files" directory
  • Soldering equipment
  • A thermal printer and required paper (DP-58C)
  • DC power supply (12V 5A) with a corresponding plug for the barrel jack
  • Wire
  • Some stripboard
  • Electronic components as shown in the PrinterPi BOM.csv and pin headers and sockets (1-pin width)
  • M2.5x12 and M2x6 machine screws
  • A sacrificial pencil for the roll holder
• 2

  Software Setup

  You will need access to the Raspberry Pi (through either SSH or console) to install the software.

  After booting up the Raspberry Pi, we need to setup the WiFi; open the WiFi configuration file:

  sudo nano /etc/wpa_supplicant/wpa_supplicant.conf
  

  And then add the following to the bottom:

  network={    ssid="YOUR_SSID_HERE"    psk="YOUR_PSK_HERE"
  }
  

  Next, get the IP address of the Raspberry Pi (and write it down; we will be using the IP address later to communicate with the extension):

  sudo ifconfig
  

  After this, run raspi-config to setup some further settings as shown in the table below

  Option	Description
  Change User Password	Change to something more secure as the Raspberry Pi will be available the network
  Hostname	Name your Pi so that it can be addressed without an IP address
  Interfacing Options -> SSH	Enable (for maintenance)
  Interfacing Options -> Serial	Disable console, enable serial
  Boot Options -> Desktop/CLI -> Console Autologin	Enable this so that the script will run automatically

  To compile the code, we need to install Java on the Raspberry Pi. Run the following commands to do this:

  Now, you can either use the precompiled code from the Releases page. (You may need to install the Java Runtime Environment with sudo apt-get install default-jre), or compile the code yourself using the method below:

  sudo apt-get update
  sudo apt-get install openjdk-8-jdk -y
  

  Finally, download a copy of the code in the "PrinterPiServer" directory in this repository and place the files in the home directory of the Raspberry Pi.

  You will need to compile the code before it can run; this can be done with the following command:

  javac *.java
  

  (continue here if using precompiled code) Additionally, we need to make the power button management script executable with the following command:

  sudo chmod +x power_button.sh
  

  To make the Raspberry Pi run the code automatically on boot, add a couple of lines of code to the .bashrc file, which runs when the user logs in (done automatically on boot up with the console autologin selection in raspi-config). Open up the file with:

  sudo nano ~/.bashrc
  

  And add the following lines to the end:

  /bin/bash /home/pi/power_button.sh&
  stty -F /dev/serial0 115200
  java -cp /home/pi Main&
  

  Finally, we need a logo for the receipt to print. Generate this from any size and color picture with the Python code in the Logo directory with the following steps:

  • Take a copy of your logo and place it into the Logo directory (rename it to Logo_in.png)
  • Next, open and run the Python program "Image Processing.py"
  • This will create a binary file, Logo.bin. You need to copy this file and place it into the directory with the other code on the Raspberry Pi for it to run

  If you do not have a logo, just create an empty file called Logo.bin on the Raspberry Pi in the same folder as the PrinterPiServer code.

  Optional additional steps

  • Use HOSTNAME.local instead of an IP address, where HOSTNAME is the hostname set with raspi-config. This should work automatically on Macs and Linux/Unix computers. For Windows machines, you will need to install Bonjour. To implement this system, change the value in IP_ADDRESS.txt to HOSTNAME.local.
  • Convert Raspberry Pi to read-only to remove the need for power button and risk of SD card corruption such as at https://medium.com/@andreas.schallwig/how-to-make-your-raspberry-pi-file-system-read-only-raspbian-stretch-80c0f7be7353
• 3

  Wiring

  First, solder together the circuit board as shown below (reference the pictures with the Wiring diagram file (Note: you will need to cut some of the traces, so please look carefully.)

  Next, solder up the power jack and thermal printer cables (power and data; these will need to be spliced) to the wires from the circuit board. The LED and power button also need to be soldered, but in this case to pin headers instead of directly to the circuit board.

  Finally, connect all corresponding cables and sockets and check that the Raspberry Pi boots and runs successfully.

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