Hooking Everything Up

The LED backpack displays are wonderfully easy to connect to the Pi. Both the 8x8 pixel and 4-character 7-segment displays are connected the same way, with two digital pins for I2C (SDA and SCL) and two power pins (VCC and GND), as follows.

If you're using a red, yellow or green backpack, you can power the backpack from 3.3V which will keep the I2C levels at 3.3V. If you have a blue or white backpack, the LEDs will be dim if powered from 3.3V.

If you want them a little brighter, connect the VCC pin of the backpack to 5V. There are 10K pullups on the backpack to 5V. As long as the backpack is the only i2c device on the i2c bus with pullups to 5V this is perfectly safe for the Pi. If you have 2 or more 5V i2c devices, the 5V pullups may 'overpower' the Pi's strong 3.3v pullups, in this case you'll want to use a proper level shifter: https://www.adafruit.com/products/757

This guide was first published on Aug 24, 2012. It was last updated on Aug 24, 2012. This page (Hooking Everything Up) was last updated on Jun 25, 2019.