Tracker One Expansion

Tracker One M8 Connector

The Tracker One can be expanded without opening the case by using the M8 connector.

Expansion Port

This connector can be used while maintaining the IP67 rating.

The 8-pin connector has these signals:

M8 Pin Function Function Function I/O
1 VIN3 I
4 CAN+ IO2
5 CAN- IO2
6 Serial1 TX Wire3 SCL GPIO D9 IO1
7 Serial1 RX Wire3 SDA GPIO D8 IO1
8 Analog A3 GPIO D3 IO1

1MCU GPIO is limited to 3.3V maximum.

2CAN Bus specifications can be found in the Tracker SoM datasheet. CAN Bus termination is provided on the carrier board.

34.5 to 30 VDC when using the M8 connector. 4.5 - 105 VDC when connecting directly to the board.

45V, 400 mA maximum. Controlled by the CAN_PWR GPIO.

M8 connector

View as looking into the M8 connector on the outside of the enclosure.

Interface Details

Power (in)

While the picture above includes both USB-C and M8 cables, it's also possible to power the Tracker One from the M8 connector. In this case, supply 4.5 to 30 VDC at 10 watts.

Power (out)

There is an optional 5V 400 mA power output (CAN 5V) that is controlled by the CAN_PWR GPIO. It is available in all power modes (battery, USB, and VIN); there is an on-board boost converter to produce 5V from the 3.7V LiPo battery.

If you are building an expansion device that is battery or USB powered, you can use CAN 5V to power your expansion device, eliminating the need to add a separate power supply. Note that this is limited to 400 mA at 5V and the Tracker SoM GPIO are limited to 3.3V, so you may need to add a 3.3V regulator on your expansion board to convert CAN 5V to 3.3V.


A CAN BUS interface is provided. The two differential CAN bus signals are provided (CAN+ and CAN-).

Multi-function pins

There are three multi-function pins:

M8 Pin Function Function Function
6 Serial1 TX Wire3 SCL GPIO D9
7 Serial1 RX Wire3 SDA GPIO D8
8 Analog A3 GPIO D3

For example: If you are using Serial1, you cannot use Wire3 (I2C) and can only use one other GPIO (D3).

If you are using Wire3 (I2C), you can't use Serial1 or D8 or D9.

If you aren't using Wire3 or Serial1, you can use all three pins as GPIO, or use D8 and D9 as GPIO and A3 as analog input (ADC).

If you are in need of more ports, the best solution is to use the multi-function pins as I2C, and include an I2C expander on your expansion board. Some things you can add using I2C:

  • More GPIO using a MCP23008 (8-port) or MCP23017 (16-port)
  • ADCs (like the MCP3021 single port)
  • PWM (pulse-width modulation output) using a PCA9685 (16-channel) for servos or LEDs
  • Temperature, humidity, and pressure sensors
  • Displays (LED, OLED, LCD, etc.)
  • Serial UART (SC16IS740)
  • FRAM non-volatile data storage

Note that Serial, I2C, GPIO, and ADC on the Tracker SoM can only be used at 3.3V maximum. The pins are not 5V tolerant!

Connecting Your Expansion Device

The M8 (8mm) 8-pin connector is standard, however it's not common. Some other connectors like M12 are more common, however, the 12mm connector would have required a taller enclosure to fit the larger connector. To simplify designs, Particle will provide a M8 female-to-wires cable, similar to this. This is for illustration only and the design may vary in the future.

M8 cable

The common use case will be to include a cable gland in your expansion enclosure, pass the wires through the gland, and terminate them on your custom expansion board.

You'd typically connect those wires to your custom expansion board using one of several methods:

  • Terminate with pins in a PHR-8 to mate with a B8B-PH on your expansion board
  • Terminate with screw terminals on your board
  • Terminate by soldering the wires to your board