HT16K33 Drivers 4.2.0

This repo provides Python drivers for the Holtek HT16K33 controller chip and various display devices based upon it, such as the Adafruit 0.8-inch 8x16 LED Matrix FeatherWing and the SparkFun Qwiic Alphanumeric Display.

The drivers support both CircuitPython and MicroPython applications. They communicate using I²C.

The library also supports generic seven-segment displays wired up to an HT16K33, which can drive up to eight these LEDs. The HT16K33 may be on a board of your own design, or on a third-party one, such as the Adafruit 16x8 LED Matrix Driver Backpack . LED units you can connect range from single digits up to combinations of multi-digit units.

Connect your HT16K33 column pins to each LED's digit selection pin, and its row pins to the LED's segment selection pins.

Major Changes

4.2.0

A new component has been added: ht16k33matrixmulti.py. This provides horizontal message scrolling across two or more matrix LEDs. Up to eight matrix LEDs can be connected, based on the range of unique I²C addresses that the HT16K33 provides. The message can be a text string or a byte array containing an 'image' comprising column-by-column bit data of the kind you might present on a single matrix LED using the HT16K33Matrix.set_icon() function.

For example, with MicroPython:

from machine import I2C, Pin, RTC
from ht16k33 import HT16K33MatrixMulti

i2c = I2C(0, scl=Pin(9), sda=Pin(8))
display = HT16K33MatrixMulti(i2c)
display.set_brightness(2).clear()

image = [0x01,0x03,0x07,0x0F,0x1D,0x3F,0x7F,0xEB,0xFF,0x77,0x3E,0x1F,0x0D,0x07,0x03,0x01,0x01,0x03,0x07,0x0D,0x0F,0x07,0x03,0x01,0x01,0x03,0x07,0x0F,0x1D,0x3F,0x7F,0xEB,0xFF,0x77,0x3E,0x1F,0x0D,0x07,0x03,0x01,0x01,0x03,0x07,0x0D,0x0F,0x07,0x03,0x01,0xC1,0xC3,0x07,0x0F,0x0F,0x07,0x03,0x01]
image_bytes = bytes(image)
display.scroll_image(image_bytes)

or for text:

display.scroll_text("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.")

The constructor takes a pre-configured I²C instance (via CircuitPython or MicroPython) and the number of matrix LEDs in your custom display panel. By default, these are assumed to be oriented left to right, with the left-most matrix using the address 0x70 and each subsequent matrix using the next sequential address. Alternatively, you can pass in an array of addresses in the sequence in which they are mounted left to right. For example, my test rig has displays with the addresses 0x70, 0x71, 0x74 and, 0x72.

The key functions, scroll_text() and scroll_image() take a string and a byte array, respectively (see the examples above). Both have two optional parameters. First, a speed value: a float that provides the pause duration in seconds between each animation frame (the default is 0.1 seconds). Second, a boolean that determines whether the image or text auto-repeats once it has completely scrolled across the face of the display (default: False). True should be used carefully as it will cause the code to block infinitely.

The new driver also includes the functions set_text() and set_image(), which take, respectively, a text string and a byte array, and a column on the display at which to draw them. set_character() works the same way, but takes an Ascii value rather than a string or a byte array. define_character() allows you to store user-defined characters in Ascii values 0 through 31.

And plot() sets or clears a pixel on the display: pass the pixel's x and y co-ordinates (0,0 is at the bottom left) and the ink colour (1 to set, 0 to clear). Optionally, pass True to reverse the target pixel if it is already set.

Finally, clear() and set_brightness() functions are provided which affect all the matrix LEDs in the display.

Display Drivers

Driver (Click for docs)	Example Product
Small 4-digit, 7-segment LED	Adafruit 0.56-inch 4-digit, 7-segment LED display
Large 4-digit, 7-segment LED	Adafruit 1.2-inch 4-digit, 7-segment LED display
Small 4-digit, 14-segment LED	SparkFun Qwiic Alphanumeric Display, Adafruit 0.54in Alphanumeric Display, EC Buying 0.54-inch HT16K33 Digital Tube Module
8x8 monochrome matrix LED	Adafruit Mini 0.8-inch 8x8 LED Matrix
Multiple 8x8 monochrome matrix LEDs	Adafruit Mini 0.8-inch 8x8 LED Matrix
8x8 bi-colour matrix LED	Adafruit 1.2-inch 8x8 bi-color LED matrix backpack
16x8 FeatherWing matrix LED	Adafruit 0.8-inch 8x16 LED Matrix FeatherWing
Standalone HT16K33	Adafruit 16x8 LED Matrix Driver Backpack
Bar graph LED	Adafruit Bi-Color 24-Bar Bargraph w/I2C Backpack

Further drivers may be added in due course.

Import the Drivers

The driver package comprises a parent generic HT16K33 class and child classes for various displays themselves. All your code needs to do is import the latter. For example:

from ht16k33 import HT16K33Segment

You can then instantiate the driver object. This requires a configured I2C bus object.

You will need at least one display driver file, eg. ht16k33segmentgen.py and ht16k33.py in your project folder.

Install the Drivers

MicroPython Manual Install

Use the pyboard or mpremote command line tools to copy the ht16k33 directory to your board's lib directory.

MicroPython MIP Install

You can install the drivers using MicroPython's MIP system. This requires a board running MicroPython 1.20 or above and connected to the Internet. Add the following to your code:

import mip
mip.install('github:smittytone/HT16K33-Python')

If your board is not Internet-capable, you can install locally using the mpremote tool:

mpremote mip install github:smittytone/HT16K33-Python

Install Script

Alternatively, use our convenient installer script:

./tools/mpinstall.sh

To install pre-compiled versions of the library files, run:

./tools/mpinstall.sh mpy

This requires MicroPython's mpy-cross tool installed on your computer.

CircuitPython Manual Install

Copy ht16k33 directory to the mounted board's lib folder.

Reducing Memory Usage

Adding the driver code may prove too much for certain CircuitPython devices which have limited amounts of memory. To overcome this, use MicroPython’s mpy-cross compiler. This will compile the raw Python into a highly compact form as a .mpy file. Copy ht16k33.mpy and the device-specific .mpy file to your device in place of the .py versions.

For MicroPython boards, I recommend you use the mpinstall.sh script to compile and install .mpy versions if the library files all in one go.

Documentation

You can find documentation for all of the drivers at smittytone.net.

Python Package Index

This code is now available via the Python Package Index for folks using Thonny and other code-pulling IDEs.

Release Notes

• 4.2.0 7 March 2025
  • Add multi-matrix scrolling enabler class.
  • Code clean.
• 4.1.0 2 January 2025
  • Add HT16K33Bar.py bar graph driver.
  • Add alternative, all-capitals character set for ht16k33Segment.py.
  • Support EC Buying 0.54in 4-digit, 14-segment display in ht16k33Segment14.py.
  • Support new board selection mode in ht16k33Segment14.py.
  • Fix decimal point clearing ht16k33Segment14.py.
• 4.0.3 18 December 2024
  • Fix typo breaking mpremote usage — thanks, @sebromero.
• 4.0.2 16 December 2024
  • Fixed a character set indexing bug in ht16k33Segmentbig.py — thanks, @jonhp.
• 4.0.1 16 August 2024
  • Minor fixes/improvements.
  • Add experimental rotate() method to ht16k33Segmentbig.py.
• 4.0.0 8 May 2024
  • Completely reorganise the library files into their own directory.
  • Add device installation script for MicroPython users - thanks, @ubidefeo.
  • Add HT16K33SegmentGen CircuitPython examples.
  • Use Raspberry Pi Pico for all examples.
• 3.5.3 15 January 2024
  • Remove the .mpy versions and provide instructions instead.
  • Fix incorrect selection of blink rate 0.5Hz — thanks, @Karrp.
• 3.5.2 11 December 2023
  • Add mip support — thanks, @ubidefeo (no code changes).
• 3.5.1 30 October 2023
  • Add provisional PyPI support (no code changes).
• 3.5.0 2 September 2023
  • Add HT16K33SegmentGen a generic, 1-8 digit 7-segment driver — thanks, @vader7071.
• 3.4.2 14 February 2023
  • Fix an error when a space is shown as a zero — thanks, @asasine.
• 3.4.1 14 November 2022
  • Correct VK16K33 naming.
  • Fix VK16K33 colon setting and unsetting — thanks, Dietmar Schüller.
• 3.4.0 6 October 2022
  • Allow the colon and decimal point on SparkFun Qwiic Alphanumeric Display).
• 3.3.1 13 September 2022
  • 14-segment character-set numerals now match 7-segment equivalents.
  • Assorted code tweaks.
  • Wrangle and extend examples.
  • Remove old docs.
  • Big thanks to @akbiocca for assistance with this release.
• 3.3.0 5 August 2022
  • Add rotate() method to HT16K33Segment.
• 3.2.0 26 July 2022
  • Support the Adafruit 0.54in Alphanumeric Display via ht16k33segment14.py.
  • Bug fixes.
• 3.1.0 16 February 2022
  • Add ht16k33segment14.py to support the SparkFun Qwiic Alphanumeric Display.
• 3.0.2 23 November 2020
  • Refactor out some ht16k33matrix.py code.
• 3.0.1 7 November 2020
  • Correct variable name in ht16k33matrix.py.
• 3.0.0 6 November 2020
  • Initial public release.

Licence and Copyright

This repository’s source code and documentation is copyright © 2025, Tony Smith (@smittytone).

The HTK16K33 driver and subsidiary display drivers are licensed under the MIT License.