SparkFun Qwiic Shield for Arduino Nano Hookup Guide
El Duderino 
Hardware Overview
The Qwiic Shield for Arduino Nano is pretty straight forward shield but has a few extra bits we'll cover in this section.
Qwiic Connectors
Just like our other Qwiic adapter boards, the Qwiic Shield for Arduino Nano comes with several Qwiic connectors. There are two horizontal Qwiic connectors on the edges of the board and two vertical ones in the center.
Logic Shifting Circuit and IOREF Jumper
The Qwiic Shield for Arduino Nano has a configurable logic shifting circuit depending on the voltage your Arduino Nano runs at. There is a jumper on the shield to set the IOREF voltage for the logic shifting circuit. The jumper defaults to 3.3V which works fine for 33 Nanos like the Arduino 33 Nano BLE but you will need to switch the jumper to 5V for Arduino Nanos that run at 5V like the Arduino Nano Every.
How to Work with Jumper Pads and PCB Traces
April 2, 2018
I2C Jumper
The I2C jumper pulls the Qwiic SDA and SCL lines up to 3.3V through 4.7K resistors. The reference voltage set by the IOREF Jumper has no effect on the voltage of the pull up resistors. You can disable them by severing the trace in between the pads if you have many devices on your I2C bus.
Board Dimensions
The shield measures 1.7in. x 0.7in. (43.18mm x 17.78mm) and has four mounting holes with a 0.07in diameter that match those on the Nano footprint.
