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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
hdmi korrekt konfigurieren wenn nach boot erst angeschlossen
zeit knopfdruck bis anzeige soweit möglich optimieren

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