Engineering Project

I2C GPIO M8 Connector Port Expander for Particle Tracker One

Schematic I2C GPIO Quad Relay

Particle Tracker One
Firmware v17
Device OS 3.2.0
LTE Cat M1 cellular modem GNSS

Supports: GPS, SBAS, QZSS, GLONASS, BeiDou, and Galileo with up to 1.8m accuracy and untethered dead-reckoning Support for CAN bus and 5V boost power for CAN devices.  This CAN_BUS_5V output via the M8 IP67 connection is what will power the port expander and subsequent devices down the line.  This eliminates the need for a mandatory external power supply, although keeping the tracker connected to vehicle power when available is always an option.  The CANbus boost power only supplies about 370mA so it is not exactly unlimited to say the least…

M8 extension cable connected to left of micro USB3 cable:



The IP67 M8, 8-pin, male with threaded barrel connector pin specifications available by clicking the image:

M8 Connector Pin-out


Circuit Schematic for the Particle Tracker One uses an MCP23008T IC for I2C/GPIO port expansion.
Instead we went with the MAX7328AWE+

We will be using the MIL SPEC version of the MAX7328, which has higher tolerances to temperature and Electromagnetic Interference (EMI).  It is manufactured by Maxim Integrated which was recently acquired by Advanced Devices.  As a developer/fabricator/researcher, Maxim has always been very helpful in providing samples and application knowledge as well as normally hard to get test circuit literature & technical documentation.  This project will tell me if this relationship still holds true after the recent politics.  So far everything seems business as usual!

MAX7328AWE+ Datasheet


As the project progresses, more information will be appended to this post.

Best Regards,

Engineer, Dr. Blöt Rèproof