LED - 3. Let's make a large led display - Part 8 (New Raspberry Pi HAT from Electrodragon )

Today, I received new RGB Matrix HATs from HongKong. Henner Zeller introduces this product on his github.




I immediately assembled this product on Raspberry Pi.



Electrodragon Vs. Adafruit
Electrodragon
Adafruit
Chain
3
1
Price ($)
3
24.95
Logic Level Shifter
74HC245
AHCT245
No. of Logic Level Shifter
4
2
Onboard 5V interface
Need soldering
Y


The price of Electrodragon is only one-eighth the price of Adafruit, but it supports three chains. Thus, one HAT can be used to connect more RGB LED matrices. If you don't have a problem with the features, of course, we recommend Electrodragon products.
The Electrodragon HAT does not have a 5V input / output terminal to supply power to the LEDs. However, this is not a problem at all, because in most cases it is supplied directly by a separate 5V power supply. I do not use HAT's 5V input / output terminals even when using Adafruit products.

Rasbian Jessie Setup

As I talked about in Part 2 of this post series, I'll be using an outdated Jessie Rasbian.
Prepare a new 16GB or larger SD card and burn the 2016-02-26-raspbian-jessie-lite image. The description of the initial settings of the Raspbian image is omitted here.

Disable Sound Driver

Open the /boot/config.txt file with an editor, change "dtparam = audio = on" to "dtparam = audio = off" and reboot.

Required Software Installation



sudo apt-get update -y
sudo apt-get dist-upgrade -y
sudo apt install build-essential libgraphicsmagick++-dev libwebp-dev -y
sudo apt install python-dev python-pip python3-dev python3-pip python3-pil -y


Download the Henner Zeller's project

I always use python3, so I'm going to bind for the Python3.


git clone https://github.com/hzeller/rpi-rgb-led-matrix

# build the project using the standard hardware profile (change based on your hardware)
cd rpi-rgb-led-matrix
sudo HARDWARE_DESC=regular make install-python

cd utils/
sudo make led-image-viewer
cd ../examples-api-use
sudo make

cd ../bindings/python
sudo make build-python PYTHON=$(which python3)
sudo make install-python PYTHON=$(which python3)


Testing the Electrodragon HAT

If you're done with the above steps, try the Electrodragon HAT. Power off the Raspberry Pi and assemble the HAT. Then connect HAT and RGB LED matrix with hub75 cable and connect 5V power to RGB LED matrix. Finally, plug in your Pi and boot it.

Run the example.


root@raspberrypi:/usr/local/src/rpi-rgb-led-matrix/examples-api-use# ./demo -D1 --led-rows=32 --led-cols=64 runtext.ppm --led-gpio-mapping=regular




You can see that it works well without any problems. The following Python program will also display the same result.


root@raspberrypi:/usr/local/src/rpi-rgb-led-matrix/bindings/python/samples# python3 image-scroller.py  --led-cols=64 --led-rows=32 --led-gpio-mapping=regular


Wrapping up

The RGB Matrix HAT doesn't really have any special features. It converts 3.3V signal of GPIO pins to 5V and transfers them to RGB LED matrix via HUB75 cable. The HC245 chip is responsible for this function. Electrodragon products are inexpensive and support three chains. I recommend you to try this product with great value. Soon, I will try to display with multiple chains and post the results again.
I've post another blog that explains "Electrodragon HAT + Raspberry Pi 4 + DietPi Buster OS" at https://iot-for-maker.blogspot.com/2020/02/led-5-raspberry-pi-4-dietpi-buster.html

You can download the source codes here(https://github.com/raspberry-pi-maker/IoT)





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