Build a beautiful, modern digital clock with a retro flair using CircuitPython, Metro M4 Airlift, RGB Matrix shield, and a 64 x 32 LED RGB pixel matrix display.

WiFi connectivity with the Metro M4 Airlift keeps your clock in sync with internet time using Adafruit IO!

Features

The METRO Matrix Clock displays the time in the IBM Plex mono typeface, using a neon green hue for daytime hours, and red for nighttime hours.

You can also enable or disable the blinking seconds colon in code.

But that's it! Just a nice, minimal clock!

Parts

Assembly

Talking to an LED matrix display can be tricky! The 64 x 32 LED used here has a whopping 2,048 pixels, and each can display RGB colors, which makes for a whole lot of data to sling around. Thankfully, our RGB Matrix shield paired with the Metro M4 Airlift does most of the heavy lifting.

Let's assemble the boards and the display so we can get things running!

Instead of the default Terminal typeface, we'll use a lovely typeface converted to a bitmap font for use on the matrix display.

In case you want to make your own font, this excellent guide shows how to use FontForge to do just that!

I selected the IBM Plex Mono Medium typeface. I then converted it to a single bitmap font in a size that works for the 64x32 pixel matrix display, and hand kerned the colon and space characters. Here is the modified .bdf font:

To use it, download and uncompress the zip file and then drag it onto the board's CIRCUITPY drive. In CircuitPython, the font is loaded so it can be used for text display.

Glyph Bitmap Distribution Format

Side note about Glyph Bitmap Distribution Format (BDF) fonts -- they are stored as text files that are human and computer readable, and you can even edit them by hand if you feel like getting super particular!

Here's what the letter 'A' glyph looks like in a typical converted .bdf font:

Each of those lines after the word BITMAP is a hexidecimal pixel mapping of a row of the glyph. Here's what that looks like converted to binary, with each row padded to 16-bits:

Glyph Tweaks

In case you wanted to add a stylish hat on top of your 'A', you could change the first row to: 1fc0 which is 0001111111000000 in binary.

Now, that's a bit of a silly example, but the great thing about this is that you can fine-tune your glyphs beyond what may be easily accomplished during the conversion process.

Libraries

We'll need to make sure we have these libraries installed. (Check out this link on installing libraries if needed.)

• adafruit_bitmap_font
• adafruit_bus_device
• adafruit_display_text
• adafruit_fakerequests.mpy
• adafruit_portalbase
• adafruit_matrixportal
• adafruit_esp32spi
• adafruit_io
• adafruit_matrixportal
• adafruit_requests.mpy
• adafruit_connection_manager.mpy
• adafruit_miniqr.mpy
• adafruit_pixelbuf.mpy
• adafruit_ticks.mpy
• neopixel.mpy
• simpleio.mpy

Connect to the Internet

Once you have CircuitPython setup and libraries installed we can get your board connected to the Internet. The process for connecting can be found here. This includes important info on the settings.toml file, adafruit IO keys, and more!

Text Editor

Adafruit recommends using the Mu editor for editing your CircuitPython code. You can get more info in this guide including info on how to use the REPL/serial terminal.

Alternatively, you can use any text editor that saves simple text files.

Code

Copy the code from the code-block below and paste it into the Mu editor and save it to your Metro M4 Airlift as code.py (or copy code.py from the zip file and place on the CIRCUITPY drive).

Using the WiFi and Adafruit IO credentials you entered into the settings.toml file and copied to the CIRCUITPY drive, your sign will connect to your WiFi, connect to Adafruit IO to get the time, and display it!

How it Works

Libraries

First we import the libraries we'll need, including time, for timekeeping, board for pin definitions on the Metro M4 Airlift, and displayio and terminalio for some of the display and basic font features.

The adafruit_display_text.label and adafruit_bitmap_font libraries are imported so we can use the text label commands and incorporate a bitmap font.

Finally adafruit_matrixportal.network and adafruit_matrixportal.matrix are imported to handle getting online through the WiFi access point to check the Adafruit IO timeserver, and to handle the lower level matrix display tasks.

Settings

Two user set variables are created next:

BLINK = True
DEBUG = False

These are at the top of the program where it's easy to change them if needed. The BLINK variable sets weather or not the colon ':' glyph will blink on and off each second.

DEBUG can be set True in order to switch from the bitmap font to the simpler terminalio font, as well as to print label bounding box and x, y coordinate values to the serial output, which is helpful when fine-tuning size and position of a bitmap font.

Check for WIFI Credentials

Next, the program checks to make sure there is SSID and password info stored in the settings.toml file that will be needed to go online. If this fails it will print an error message to the serial output.

Display & Network Setup

The matrix display and matrix objects are created next with these commands:

The displayio Group, Bitmap, Palette, and TileGrid are created so we have the proper objects and hierarchy to display the time on the display. For info on this, check out the excellent displayio guide!

BDF Font Load

Now we'll load the BDF font glyphs from the Metro M4 Airlift's storage, in this case the lovely IBM Plex Mono medium in 24 point. (If we're in DEBUG mode, the terminalio font is used instead.)

The clock_label text object is created using the font so we have an object to display the time.

Update Time

The update_time() function will do all of the heavy lifting of parsing the current time value into discreet hours, minutes, and optional colon chunks that can be fed as arguments into the clock_label.text command.

This function also handles the blinking logic for the second hand colon, and sets the color of the text label to day vs. evening hours.

Text Centering

There's a very handy command we'll use for centering the text on the display: clock_label.bounding_box. This returns the x- and y-positions of the label, as well as the width and height of it's bounding box (an imaginary rectangle that encompasses the label).

With this we can then use a couple of simple formulas to set the label's x and y coordinates to be centered on the display. These essentially divide the display in half an the label in half to find their centers.

Initial Display

The last_check variable is created to keep track of the state of time elapsed since last lookup of Adafruit IO timeserver time.

The update_time() function is called, and then the clock_label is appended to the display group so it will appear. At first this will be based on the Metro M4 time, which will be 12:00 when first powered on. But soon, we'll run the network time check to get accurate!

Main Loop

After all of that setup, it's time to get the time! This is the main loop of the program that runs over and over. The first thing to do is check the time if the last_check variable is either None or one hour has elapsed (3600 seconds).

The network.get_local_time() command uses the WiFi connection to synchronize to Adafruit IO timeserver time. Then the last_check value is reset to the current time.monotonic() (think of it as a continuously running ticker).

The display is then refreshed with the current time, and the process is repeated every second, taking a look each hour at the timeserver.