Connecting a Matrix Orbital Display to a Raspberry Pi

If you’ve ever wondered how to connect a Matrix Orbital display to your Raspberry Pi, then this is the post for you. No more sleepless nights.

I’m a big fan of the Matrix Orbital vacuum fluorescent displays because they have a really cool retro vibe and I use them in a lot of projects. Connecting to a Pi is a snap because of the board’s architecture.

You have multiple options depending on the board – either I2C, serial or USB. In this post I’m going to focus specifically on serial and I2C because these are available on the less expensive older boards – which I typically buy.

These instructions should work with any older VK204-25 board. See this link for the VK-204 technical manuals.

The image on the right shows the back of the display module with the DB9 (serial) connector on the left and the 4 pin I2C connector (white) on the right.

Matrix Orbital VK204-25 Display
Matrix Orbital VK204-25 DB9 (left) and I2C (right)

I2C

To connect via I2C you’ll need to first enable the interface on the Pi. This is done via raspi-config which can be run in a terminal window:

sudo raspi-config

In the raspi-config user interface navigate to Interfacing Options >> I2C and answer the question "Would you like the ARM I2C interface to be enabled?" with <Yes>. After the next reboot user pi will be able to use the I2C bus without root privileges.

When connecting the display, you’ll need to find the correct GPIO pins depending on the version Pi you’re using. Needed are SCL, SDA , 5V and ground. Note: For this example I’ll be connecting to an older Pi (model B) that has a 26 pin header. More recent Pis will have a different GPIO configuration – make sure to read the documentation.

Behind the display on the lower right, there’s a white colored 4 pin connector. The ground is the pin furthest to the right and labeled on the PCB. The correct connections are: Pin1 5VDC, Pin2 SCL, Pin3 SDA and Pin4 Ground.

Run the following command from your Pi in a terminal to confirm that you have it wired up correctly:

i2cdetect -y 1

This will return a hex address that’s needed when sending commands to the display.

Serial (DB9)

For an alternative serial connection, there’s a DB9 port on the lower right of the display. See the diagrams to the right for the pin orientation and how to connect. You’ll be using the same 5v and ground connections as the I2C setup, but you’ll also need to connect the Pi TX pin to the DB9 pin 3, the Pi RX pin to DB9 pin 2, and a ground to DB9 pin 5.

Raspberry Pi Model B using I2C
Rasbperry Pi Model B using DB9 (Serial)
LCD DB9 Pin Orientation

These two options cover everything needed for connecting the display. The only gotcha is that some of the older boards might require jumper changes or even soldering some pull up resistors depending on the chosen communication method. I would recommend reading the documentation carefully as these requirements can be different depending on the board version.

Hopefully you found this post helpful. Check out my engineering posts for other useful how-tos.

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