We'll cover how to wire the OLED to your CircuitPython microcontroller board. First assemble your OLED.

Connect the OLED to your microcontroller board as shown below.

I2C Wiring

Use this wiring if you want to connect via I2C interface

  • Connect Vin (red wire on STEMMA QT version) to the power supply, 3-5V is fine. Use the same voltage that the microcontroller logic is based off of.
  • Connect GND (black wire on STEMMA QT version) to common power/data ground
  • Connect the Clk (yellow wire on STEMMA QT version) pin to the I2C clock SCL pin on your Microcontroller.
  • Connect the Data (blue wire on STEMMA QT version) pin to the I2C data SDA pin on your Microcontroller.

SPI Wiring

Since this is a SPI-capable display, we can use SPI. The following pins should be used:

  • Connect Vin to the power supply, 3-5V is fine. Use the same voltage that the microcontroller logic is based off of.
  • Connect GND to common power/data ground
  • Connect the Clk pin to the SPI clock SCK pin on your Microcontroller. 
  • Connect the Data pin to the SPI data MOSI pin on your Microcontroller.
  • Connect the CS pin to D5 on your Microcontroller. If you don't have this pin on your Microcontroller, feel free to use a different one and update the example.
  • Connect the DC pin to D6 on your Microcontroller. If you don't have this pin on your Microcontroller, feel free to use a different one and update the example.
  • Connect the Rst pin to D9 on your Microcontroller. If you don't have this pin on your Microcontroller, feel free to use a different one and update the example.
If you want to use the board in SPI. mode, you need to cut J1 and J2 first. See Pinouts for more details.
To use this grayscale OLED display with displayio, you will need to use the absolute latest version of CircuitPython and a board that can fit `displayio`. See the Support Matrix to determine if `displayio` is available on a given board: https://circuitpython.readthedocs.io/en/latest/shared-bindings/support_matrix.html

CircuitPython displayio Library Installation

To use displayio, you will need to install the appropriate library for your display. 

First make sure you are running the latest version of Adafruit CircuitPython for your board. You will need the latest version of CircuitPython.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  Our introduction guide has a great page on how to install the library bundle for both express and non-express boards.

You will need to copy the appropriate displayio driver from the bundle lib folder to a lib folder on your CIRCUITPY drive. The displayio driver contains the initialization codes specific to your display that are needed to for it to work. Since there is more than one driver, you will need to copy the correct file over. Here is a list of each of the displays and the correct driver for that display.

When downloading CircuitPython, for Grayscale support you will need to choose Absolute Newest, choose your language, and then download the top-most link.

Adafruit_CircuitPython_SSD1327

This display uses the Adafruit_CircuitPython_SSD1327 library. Copy the adafruit_ssd1327.mpy file from the bundle to the lib folder on your CIRCUITPY drive.

Code Example Additional Libraries

For the Code Example, you will need an additional library. We decided to make use of the the Adafruit CircuitPython Display Text library so the code didn't get overly complicated. Go ahead and install that in the same manner as the driver library by copying the adafruit_display_text folder over to the lib folder on your CircuitPython device.

Displayio is only available on express board due to the smaller memory size on non-express boards.

Usage

It's easy to use OLEDs with Python and the Adafruit CircuitPython SSD1327 module.  This module allows you to easily write Python code to control the display.

To demonstrate the usage, we'll initialize the library and use Python code to control the OLED from the board's Python REPL.

I2C Initialization

If your display is connected to the board using I2C, you'll first need to initialize the I2C bus.  First import the necessary modules:

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import board

Now for run this command to create the I2C instance using the default SCL and SDA pins (which will be marked on the board's pins if using a Feather or similar Adafruit board):

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i2c = board.I2C()

After initializing the I2C interface for your firmware as described above, you can create an instance of the I2CDisplay bus:

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import displayio
import adafruit_ssd1327
display_bus = displayio.I2CDisplay(i2c, device_address=0x3D)

Finally, you can pass the display_bus in and create an instance of the SSD1327 I2C driver by running:

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display = adafruit_ssd1327.SSD1327(display_bus, width=128, height=128)

Now you should be seeing an image of the REPL. Note that the last two parameters to the SSD1327 class initializer are the width and height of the display in pixels.

Changing the I2C address

If you connect the A0 Pin of the OLED to Ground instead of +3V or create a solder bridge on the back of the display for the A0 jumper the I2C address will be different different (0x3c):

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display_bus = displayio.I2CDisplay(i2c, device_address=0x3c)
display = adafruit_ssd1327.SSD1327(display_bus, width=128, height=128)

At this point the I2C bus and display are initialized. Skip down to the example code section.

SPI Initialization

If your display is connected to the board using SPI you'll first need to initialize the SPI bus. 

If you're using a microcontroller board, run the following commands:

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import board
import displayio
import adafruit_ssd1327

displayio.release_displays()

spi = board.SPI()
oled_cs = board.D5
oled_dc = board.D6
oled_reset = board.D9

display_bus = displayio.FourWire(spi, command=oled_dc, chip_select=oled_cs,
                                 reset=oled_reset, baudrate=1000000)
display = adafruit_ssd1327.SSD1327(display_bus, width=128, height=128)

The parameters to the FourWire initializer are the pins connected to the display's DCCS, and reset. Because we are using keyword arguments, they can be in any position.  Again make sure to use the right pin names as you have wired up to your board!

Note that the last two parameters to the SSD1327 class initializer are the width and height of the display in pixels.

Example Code

import board
import displayio
import terminalio
from adafruit_display_text import label
import adafruit_ssd1327

displayio.release_displays()

# Use for I2C
i2c = board.I2C()
display_bus = displayio.I2CDisplay(i2c, device_address=0x3D)

# Use for SPI
# spi = board.SPI()
# oled_cs = board.D5
# oled_dc = board.D6
# display_bus = displayio.FourWire(
#    spi, command=oled_dc, chip_select=oled_cs, baudrate=1000000, reset=board.D9
# )

WIDTH = 128
HEIGHT = 128
BORDER = 8
FONTSCALE = 1

display = adafruit_ssd1327.SSD1327(display_bus, width=WIDTH, height=HEIGHT)

# Make the display context
splash = displayio.Group(max_size=10)
display.show(splash)

# Draw a background rectangle, but not the full display size
color_bitmap = displayio.Bitmap(
    display.width - BORDER * 2, display.height - BORDER * 2, 1
)
color_palette = displayio.Palette(1)
color_palette[0] = 0xFFFFFF  # White
bg_sprite = displayio.TileGrid(
    color_bitmap, pixel_shader=color_palette, x=BORDER, y=BORDER
)
splash.append(bg_sprite)

# Draw a smaller inner rectangle
inner_bitmap = displayio.Bitmap(
    display.width - BORDER * 4, display.height - BORDER * 4, 1
)
inner_palette = displayio.Palette(1)
inner_palette[0] = 0x888888  # Gray
inner_sprite = displayio.TileGrid(
    inner_bitmap, pixel_shader=inner_palette, x=BORDER * 2, y=BORDER * 2
)
splash.append(inner_sprite)

# Draw a label
text = "Hello World!"
text_area = label.Label(terminalio.FONT, text=text, color=0xFFFFFF)
text_width = text_area.bounding_box[2] * FONTSCALE
text_group = displayio.Group(
    max_size=10,
    scale=FONTSCALE,
    x=display.width // 2 - text_width // 2,
    y=display.height // 2,
)
text_group.append(text_area)  # Subgroup for text scaling
splash.append(text_group)

while True:
    pass

Let's take a look at the sections of code one by one. We start by importing the board so that we can initialize SPI, displayio,terminalio for the font, a label, and the adafruit_ssd1327 driver.

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import board
import displayio
import terminalio
from adafruit_display_text import label
import adafruit_ssd1327

Next we release any previously used displays. This is important because if the microprocessor is reset, the display pins are not automatically released and this makes them available for use again.

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displayio.release_displays()

If you're using I2C, you would use this section of code. We set the I2C object to the board's I2C with the easy shortcut function board.I2C(). By using this function, it finds the SPI module and initializes using the default SPI parameters. We also set the display bus to I2CDisplay which makes use of the I2C bus.

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# Use for I2C
i2c = board.I2C()
display_bus = displayio.I2CDisplay(i2c, device_address=0x3D)

If you're using SPI, you would use this section of code. We set the SPI object to the board's SPI with the easy shortcut function board.SPI(). By using this function, it finds the SPI module and initializes using the default SPI parameters. We set the OLED's CS (Chip Select), and DC (Data/Command) pins. We also set the display bus to FourWire which makes use of the SPI bus. The SSD1327 needs to be slowed down to 1MHz, so we pass in the additional baudrate parameter. We also pass board.D9 as the reset pin. If this differs for you, you could change it here.

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# Use for SPI
spi = board.SPI()
oled_cs = board.D5
oled_dc = board.D6
display_bus = displayio.FourWire(
   spi, command=oled_dc, chip_select=oled_cs, baudrate=1000000, reset=board.D9
)

In order to make it easy to change display sizes, we'll define a few variables in one spot here. We have WIDTH, which is the display width, HEIGHT, which is the display height and BORDER, which we will explain a little further below. FONTSCALE will be the multiplier for the font size.

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WIDTH = 128
HEIGHT = 128
BORDER = 8
FONTSCALE = 1

Finally, we initialize the driver with a width of the WIDTH variable and a height of the HEIGHT variable. If we stopped at this point and ran the code, we would have a terminal that we could type at and have the screen update. You may notice Blinka is grayscale.

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display = adafruit_ssd1327.SSD1327(display_bus, width=WIDTH, height=HEIGHT)

Next we create a background splash image. We do this by creating a group that we can add elements to and adding that group to the display. In this example, we are limiting the maximum number of elements to 10, but this can be increased if you would like. The display will automatically handle updating the group.

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# Make the display context
splash = displayio.Group(max_size=10)
display.show(splash)

Next we create a Bitmap that is the full width and height of the display minus the value of the BORDER variable for each of the 2 sides. The Bitmap is like a canvas that we can draw on. In this case we are creating the Bitmap to be the same size as the screen, but only have one color. Although the Bitmaps can handle up to 256 different colors, we only need one. We create a Palette with one color and set that color to 0xFFFFFF, which happens to be white. If were to place a different color here, displayio handles color conversion automatically, so it would end up some shade of gray.

With all those pieces in place, we create a TileGrid by passing the bitmap and palette and draw it at (8, 8) so that it ends up centered.

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# Draw a background rectangle, but not the full display size
color_bitmap = displayio.Bitmap(
    display.width - BORDER * 2, display.height - BORDER * 2, 1
)
color_palette = displayio.Palette(1)
color_palette[0] = 0xFFFFFF  # White
bg_sprite = displayio.TileGrid(
    color_bitmap, pixel_shader=color_palette, x=BORDER, y=BORDER
)
splash.append(bg_sprite)

Next we will create a smaller gray rectangle. The easiest way to do this is to create a new bitmap that is a little smaller than the full screen with a single color of 0x888888, which is gray, and place it in a specific location.  This display handles grayscale and this color is about halfway between 0x000000 and 0xFFFFFF. In this case, we will create a bitmap that is 8 pixels smaller on each side than the previous rectangle for a difference of 16 pixels on each side. We have the BORDER set to 8 , so we'll want to subtract 32 from each of those numbers.

We'll want to place it at the position (16, 16) so that it ends up centered as well.

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# Draw a smaller inner rectangle
inner_bitmap = displayio.Bitmap(
    display.width - BORDER * 4, display.height - BORDER * 4, 1
)
inner_palette = displayio.Palette(1)
inner_palette[0] = 0x888888  # Gray
inner_sprite = displayio.TileGrid(
    inner_bitmap, pixel_shader=inner_palette, x=BORDER * 2, y=BORDER * 2
)
splash.append(inner_sprite)

Since we are adding this after the first square, it's automatically drawn on top. Here's what it looks like now. Because of the way the OLED scans, you may notice the colors aren't distributed evenly.

Next let's add a label that says "Hello World!" on top of that. We're going to use the built-in Terminal Font and scale it up by a factor of two, which is what we have FONTSCALE set to. To scale the label only, we will make use of a subgroup, which we will then add to the main group.

We create the label first so that we can get the width of the bounding box and multiply it by the FONTSCALE. This gives us the actual with of the text.

Labels are automatically centered vertically, so we'll place it at half the display height for the Y coordinate, and we calculate the X coordinate to horizontally center the label. We use the // operator to divide because we want a whole number returned and it's an easy way to round it. Let's go with some white text.

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# Draw a label
text = "Hello World!"
text_area = label.Label(terminalio.FONT, text=text, color=0xFFFFFF)
text_width = text_area.bounding_box[2] * FONTSCALE
text_group = displayio.Group(
    max_size=10,
    scale=FONTSCALE,
    x=display.width // 2 - text_width // 2,
    y=display.height // 2,
)
text_group.append(text_area)  # Subgroup for text scaling
splash.append(text_group)

Finally, we place an infinite loop at the end so that the graphics screen remains in place and isn't replaced by a terminal.

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while True:
    pass

Where to go from here

Be sure to check out this excellent guide to CircuitPython Display Support Using displayio

This guide was first published on Nov 10, 2020. It was last updated on Nov 10, 2020.

This page (CircuitPython Wiring and Usage) was last updated on Nov 10, 2020.