RasPi Freezer

Usage Instructions

• Plug HDMI into Beamer
• Plug USB into Computer
• booting the Raspberry takes approximately 25 seconds. the green led will light up when ready
• start freeze.exe from the (newly attached) USB-Drive
• press button on device or ALT+X or Alt+PRINTSCREEN to take a screenshot
• simply unplug after use

Other features

• you can call freeze.exe with the cmdline argument "single" to just do one screenshot, save it and exit

Initial setup

Parts

• Mini-HDMI <-> HDMI Adapter
• Mini-USB <-> USB A Cable
• Micro-SD-Card >= 2GB
• Raspberry Pi Zero or Zero W or Model A (Model B/2B/3 not supported!)

Hardware

       LED     LED SW
 ______||_______|||____
| :::::::::::::::::::: |
|                      |
|_HDMI________USB__PWR_|
   |           |   nc
   v           v
 Beamer        PC

Build windows snapshot-tool

cd windows-snapshot-tool mkdir build && cd build cmake -DCMAKE_TOOLCHAIN_FILE=../Toolchain-cross-mingw32-linux.cmake ../ make

prepare raspberry pi

install raspbian lite

sudo raspi-config

• ??
• ??

sudo su - apt update apt dist-upgrade apt install python3-pyinotify python3-rpi.gpio apt clean

echo "dtoverlay=dwc2" >> /boot/config.txt

echo "dtoverlay=gpio-poweroff,gpiopin=5,active_low" >> /boot/config.txt

sed -i /boot/config.txt -e "s/^hdmi_force_hotplug=1$/hdmi_force_hotplug=1$/"

echo "libcomposite" >> /etc/modules

apt purge plymouth systemctl disable getty@tty1

add/change in /boot/cmdline.txt: console=tty3 consoleblank=0 loglevel=3 vt.global_cursor_default=0 (logo.nologo to disable the raspberry)

copy everything to /opt/freezer/ chmod a+x /opt/freezer/display.py add to /etc/rc.local: cd /tmp && nohup python3 /opt/freezer/display.py 2>&1 &

read-only root

wget https://raw.githubusercontent.com/adafruit/Raspberry-Pi-Installer-Scripts/master/read-only-fs.sh
sudo bash read-only-fs.sh

• continue: y
• jumper: n
• gpio-halt: n
• watchdog: n
• continue: y

this is how to remount read-write later to make changes to the fs

mount -o remount,rw / mount -o remount,rw /boot

ToDo

• korrekte auflösung bei desktop-scaling
• zu viel overscan
• hdmi korrekt konfigurieren wenn nach boot erst angeschlossen
• zeit knopfdruck bis anzeige soweit möglich optimieren