wuub / python_lcd

Python based library for talking to character based LCDs.

lcd and i2c_lcd

Python code for talking to character based LCDs.

The I2c_Lcd class allows for talking to i2c based LCDs.

This was tested on a BeagleBone Black using a 2 x 16 LCD with an i2c module similar to this one.

This code was adapted from some C code that I had written previously for the AVR.

To install on your BBB:

git clone https://github.com/dhylands/python_lcd.git
cd python_lcd
sudo pip install -e .

And to test:

sudo lcd/i2c_lcd.py

Since my LCD was a 5v device, I used a level converter to convert from BBB's 3.3v to the LCD's 5v.

I put together some [photos here] (https://picasaweb.google.com/115853040635737241756/PythonI2CLCD?authkey=Gv1sRgCLyZoJ3_uPjiXA)

Coming from the BeagleBone Black the wire colors are:

Color  Pin   Name
------ ----- ------
Black  P9-1  GND
Red    P9-3  3.3v
Orange P9-7  SYS_5V
Yellow P9-19 SCL
White  P9-20 SDA

The photo shows Orange connected to P9-5. I discovered that P9-7 is controlled by the onboard voltage regulators, so when you do a "sudo poweroff" then SYS_5V drops to 0v when the BBB is powered off. P9-5 (VDD_5V) remains at 5v after the BBB is powered off.

And the colors going to the LCD are:

Color  Name
------ ----
Black  GND
Red    5v
White  SDA
Yellow SCL

I used a SparkFun level shifter (this particular model is no longer available).

Some examples of other level shifters which could be used:

• Logic Level Converter
• Logic Level Converter Bi-Directional
• Voltage-Level Translator - TXB0104 Breakout
• PCA9306 Level Translator Breakout
• 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138
• 8-channel Bi-directional Logic Level Converter - TXB0108