website/input/projects/ledmatrix_v2.md

title: RGB LED Matrix visualizer description: For HUB75 modules, running on Raspberry Pi and Pico W parent: projects git: https://git.xythobuz.de/thomas/rgb-matrix-visualizer date: 2023-09-05

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I initially bought a 32x32 RGB LED matrix in 2018. Back then the idea was to fit it onto a bag, as some kind of wearable device, for 35C3. But it never really worked out. So in preparation for CCCamp23 I noticed the LED panel again and decided to order some more of them.

These are the 32x32 4mm pitch RGB LED Matrix Panels from Pimoroni, with either the Interstate 75 W or the Adafruit RGB Matrix Bonnet to run them with a RP2040 or a Raspberry Pi, respectively.

Everything runs from a single Python codebase, either simulated in a GUI window on a development PC, on the Raspbian Python interpreter or directly on the Pico MicroPython environment.

For portability I’m simply using a voltage regulator to connect a 4S LiPo battery. I made one of them from recycled single-use vape batteries, but I also used some of my RC-model batteries.

On the software side I wrote some code to show static images, GIF animations, scroll text across the matrix, etc. I also implemented Snake, Tetris and Breakout, as well as some other utilities, like OTA updating for the Pico, a Telegram bot integration, a weather widget and a service checking if a device is reachable on the network.

Right now the 64x64 panel is placed next to the TV in my livingroom, randomly cycling through some animations and games.

I wasn’t really able to get breakout into a playable state before CCCamp23. But luckily I also got a patch set (1, 2, 3, 4) from Jannis that fixed the collision behaviour of the ball in breakout! We met on the camp and had a very nice time together. And soon afterwards the patches appeared in my inbox and actually made the game playable! This was really awesome 😊💪 Thanks again!

Here are my notes for installing everything on a Raspbian OS.

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install python3-pip git vim htop
git clone https://github.com/adafruit/Raspberry-Pi-Installer-Scripts
cd Raspberry-Pi-Installer-Scripts
sudo ./rgb-matrix.sh
# Answer y, Bonnet, Quality (and solder the mentioned link on the board)
cd ..

git clone https://git.xythobuz.de/thomas/rgb-matrix-visualizer
sudo pip3 install Pillow bdfparser "qrcode[pil]" evdev

cd Raspberry-Pi-Installer-Scripts/rpi-rgb-led-matrix/bindings/python
pip3 wheel --no-deps -w dist .
sudo pip3 install dist/rgbmatrix-0.0.1-cp39-cp39-linux_armv7l.whl

sudo apt-get install libopenjp2-7

# append isolcpus=3 to /boot/cmdline.txt
cat <<EOF | sudo tee /etc/modprobe.d/blacklist-rgb-matrix.conf
blacklist snd_bcm2835
EOF

sudo update-initramfs -u
sudo reboot

# test python bindings work
cd rgb-matrix-visualizer
sudo ./pi.py

sudo sh -c 'echo enable_uart=1 >> /boot/config.txt'

Although I’m currently still having some problems getting the wetterdienst dependency running on the Raspberry Pi.

I also want to give a shout-out to Pimoroni. I managed to rip-off the power connector on one of the panels. They sent a replacement without any additional cost, but I took the chance and ordered some more spare panels.

The modules bought this year have pretty consistent color reproduction. But compared to the one module I bought five years earlier, there is a very noticable difference. On these pictures both modules show the same RGB values.

I added some simple compensation to mostly adjust for this issue.

# For some reason the red and green LEDs on older Pimoroni panels
# are far brighter than on newer panels.
# Adjust this by multiplying rg channels with 0.75 and b channel
# with 0.85, depending on hard-corded coordinate ranges.
class MapperColorAdjust(MapperNull):
    def set_pixel(self, x, y, color):
        # second panel from the left, with 32 <= x,
        # is "old" type with brighter LEDs.
        # rest of panels to the left are less bright.
        # so adjust brightness of other panel channels down.
        if x >= self.gui.panelW:
            color = (int(color[0] * 0.75), int(color[1] * 0.75), color[2] * 0.85)

        self.gui.set_pixel(x, y, color)

I also planned to build a large LED matrix based on WS2812 LED strips. They can be driven easily with a Raspberry Pi.

I was even able to get a basic frame finished before CCCamp23. But that’s where time ran out.

I haven’t yet given up that plan completely, but I have to think of a solution for diffusing the light first. The LEDs are too small and spaced too far apart to look good in this configuration.

More Pictures

Some more photographs I didn't use above.