The Vernier Arduino® Interface Shield (BT-ARD), has four sensor ports; two analog and two digital. The shield connects the sensor lines to the following Arduino pins:

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Analog 1
Sensor pin 1 (+/-10 V output line) – Arduino pin A1
Sensor pin 2 (Ground) – Arduino ground
Sensor pin 3 (Vres/resistance reference) – Arduino pin A4
(also for I2C autoID)
Sensor pin 4 (AutoID) – Arduino pin A5 (also for I2C autoID)
Sensor pin 5 (+5 Volt power) – Ardino 5V
Sensor pin 6 (0-5 V output line) – Arduino pin A0

Analog 2
Sensor pin 1 (+/-10 V output line) – Arduino pin A3
Sensor pin 2 (Ground) – Arduino ground
Sensor pin 3 (Vres/resistance reference and I2C input line- Arduino pin A4)
Sensor pin 4 (AutoID) and I2C output line– Arduino pin A5)
Sensor pin 5 (+5 Volt power) – Ardino 5V
Sensor pin 6 (0-5 V output line) – Arduino pin A2

Digital 1
Sensor pin 1 (Input/Output Line 0) – Arduino pin D2
Sensor pin 2 (Input/Output Line 1) – Arduino pin D3/A4
Sensor pin 3 (Input/Output Line 2) – Arduino pin D4/A5
Sensor pin 4 (+5 Volt power) – Ardino 5V
Sensor pin 5 (Ground) – Arduino ground
Sensor pin 6 (Input/Output Line 3) – Arduino pin D5

Digital 2
Sensor pin 1 (Input/Output Line 0) – Arduino pin D6
Sensor pin 2 (Input/Output Line 1) – Arduino pin D7/A4
Sensor pin 3 (Input/Output Line 2) – Arduino pin D8/A5
Sensor pin 4 (+5 Volt power) – Ardino 5V
Sensor pin 5 (Ground) – Arduino ground
Sensor pin 6 (Input/Output Line 3) – Arduino pin D9

Notes:
*Details for Vernier sensor pinouts can be found here: https://www.vernier.com/support/sensor-pinouts/
*Most analog sensors use the 0-5 V output line.
*Digital sensors vary in how they use the four IO lines.
*Vernier interfaces use sensor pin 3 and 4 to auto-ID connected sensors. These pins are connected to Arduino pins A4 and A5; sample Arduino code for auto-ID’ing sensors can be found here. For many modern Vernier sensors, lines A4 and A5 use I2C communication to identify sensors. On some Arduino types, notably Arduino Mega, these pins cannot be used for I2C communication, so these sensors will not AutoID. Arduino Mega uses different pins for I2 communications.
*Pins A4 and A5 are shared across all four connectors. In order to properly access the BTA and BTD connector pins, you will need to interface the analog multiplexer circuit; MUX Control addresses are D10 and D11.
*An LED indicator is tied to D13 and a general purpose button is connected to D12.

For more information about how Vernier sensors work with Arduino, see our sample code and projects or SparkFun’s tutorial.