SSD1306 / SH1106 OLED Driver

Interfacing OLED matrix displays with the SSD1306 (or SH1106) driver in Python 2 or 3 using I2C on the Raspberry Pi. The particular kit I bought can be acquired for a few pounds from eBay. Further technical details for the SSD1306 OLED display can be found in the datasheet [PDF]. See also the datasheet [PDF] for the SH1106 chipset.

The SSD1306 display is 128x64 pixels, and the board is tiny, and will fit neatly inside the RPi case (the SH1106 is slightly different, in that it supports 132 x 64 pixels). My intention is to solder wires directly to the underside of the RPi GPIO pins so that the pins are still available for other purposes.

GPIO pin-outs

The SSD1306 device is an I2C device, so connecting to the RPi is very straightforward:

P1 Header

For prototyping, the P1 header pins should be connected as follows:

Board Pin	Name	Remarks	RPi Pin	RPi Function	Colour
1	GND	Ground	P01-6	GND	Black
2	VCC	+3.3V Power	P01-1	3V3	White
3	SCL	Clock	P01-5	GPIO 3 (SCL)	Purple
4	SDA	Data	P01-3	GPIO 2 (SDA)	Grey

P5 Header

On rev.2 RPi's, right next to the male pins of the P1 header, there is a bare P5 header which features I2C channel 0, although this doesn't appear to be initially enabled and may be configured for use with the Camera module.

Board Pin	Name	Remarks	RPi Pin	RPi Function	Colour
1	GND	Ground	P5-07	GND	Black
2	VCC	+3.3V Power	P5-02	3V3	White
3	SCL	Clock	P5-04	GPIO 29 (SCL)	Purple
4	SDA	Data	P5-03	GPIO 28 (SDA)	Grey

Pre-requisites

This was tested with Raspian on a rev.2 model B, with a vanilla kernel version 4.1.16+. Ensure that the I2C kernel driver is enabled:

$ dmesg | grep i2c
[    4.925554] bcm2708_i2c 20804000.i2c: BSC1 Controller at 0x20804000 (irq 79) (baudrate 100000)
[    4.929325] i2c /dev entries driver

or:

$ lsmod | grep i2c
i2c_dev                 5769  0
i2c_bcm2708             4943  0
regmap_i2c              1661  3 snd_soc_pcm512x,snd_soc_wm8804,snd_soc_core

If you have no kernel modules listed and nothing is showing using dmesg then this implies the kernel I2C driver is not loaded. Enable the I2C as follows:

1. Run sudo raspi-config
2. Use the down arrow to select 9 Advanced Options
3. Arrow down to A7 I2C
4. Select yes when it asks you to enable I2C
5. Also select yes when it asks about automatically loading the kernel module
6. Use the right arrow to select the <Finish> button
7. Select yes when it asks to reboot

After rebooting re-check that the dmesg | grep i2c command shows whether I2C driver is loaded before proceeding.

Optionally, to improve permformance, increase the I2C baudrate from the default of 100KHz to 400KHz by altering /boot/config.txt to include:

dtparam=i2c_arm=on,i2c_baudrate=400000

Then reboot.

Then add your user to the i2c group:

$ sudo adduser pi i2c

Install some packages (python2):

$ sudo apt-get install i2c-tools python-smbus python-pip libfreetype6-dev
$ sudo pip install pillow

or (python3):

$ sudo apt-get install i2c-tools python3-smbus python3-pip libfreetype6-dev
$ sudo pip3 install pillow

Next check that the device is communicating properly (if using a rev.1 board, use 0 for the bus not 1):

$ i2cdetect -y 1
       0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
  00:          -- -- -- -- -- -- -- -- -- -- -- -- --
  10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
  20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
  30: -- -- -- -- -- -- -- -- -- -- -- UU 3c -- -- --
  40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
  50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
  60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
  70: -- -- -- -- -- -- -- --

According to the manual, "UU" means that probing was skipped, because the address was in use by a driver. It suggest that there is a chip at that address. Indeed the documentation for the device indicates it uses two addresses.

Installing the Python Package

For python2, from the bash prompt, enter:

$ sudo python setup.py install

This will install the Python files in /usr/local/lib/python2.7 making them ready for use in other programs.

Alternatively for python3, type:

$ sudo python3 setup.py install

Software Display Driver

The screen can be driven with python using the oled/device.py script. There are two device classes and usage is very simple if you have ever used Pillow or PIL.

First, import and initialise the device:

from oled.device import ssd1306, sh1106
from oled.render import canvas
from PIL import ImageFont, ImageDraw

# substitute sh1106(...) below if using that device
device = ssd1306(port=1, address=0x3C)  # rev.1 users set port=0

The display device should now be configured for use. The specific ssd1306 or sh1106 classes both expose a display() method which takes a 1-bit depth image. However, for most cases, for drawing text and graphics primitives, the canvas class should be used as follows:

with canvas(device) as draw:
    font = ImageFont.load_default()
    draw.rectangle((0, 0, device.width, device.height), outline=0, fill=0)
draw.text((30, 40), "Hello World", font=font, fill=255)

The canvas class automatically creates an ImageDraw object of the correct dimensions and bit depth suitable for the device, so you may then call the usual Pillow methods to draw onto the canvas.

As soon as the with scope is ended, the resultant image is automatically flushed to the device's display memory and the ImageDraw object is garbage collected.

Run the demos in the example directory:

$ python examples/demo.py
$ python examples/sys_info.py
$ python examples/pi_logo.py
$ python examples/maze.py

Notes

1. Substitute python3 for python in the above examples if you are using python3.
2. python-dev (apt-get) and psutil (pip/pip3) are required to run the sys_info.py example.

See install instructions for the exact commands to use.

References

• https://learn.adafruit.com/monochrome-oled-breakouts
• https://github.com/adafruit/Adafruit_Python_SSD1306
• http://www.dafont.com/bitmap.php
• http://raspberrypi.znix.com/hipidocs/topic_i2cbus_2.htm
• http://martin-jones.com/2013/08/20/how-to-get-the-second-raspberry-pi-i2c-bus-to-work/

License

The MIT License (MIT)

Copyright (c) 2016 Richard Hull

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.