February 19, 2018

Physically Connecting Machines: The Basics of the CAN Bus

Tech Talk

Even if you have a high-level understanding of telematics, you might still lack some clarity on how exactly your machine’s data gets recorded and extracted.

Here’s the short answer: The data collection process is made possible by the machine’s controller area network, or CAN bus. But unless you’re an engineer, that answer probably doesn’t mean much to you. So we’ve created a layman’s guide to this vital link between your fleet and your telematics platform.

What is a CAN bus?

Most construction vehicles have dozens of sensors and electronic control units (ECUs) overseeing various parts of the machine — like the powertrain module, speed control unit and battery management system. A CAN bus connects all of these sensors and ECUs and allows them to share data with each other.

Think of it this way: If your equipment is a human body, the CAN bus is its nervous system. It’s what allows all of the organs to communicate with each other and report back to the brain. 

How does a CAN bus work?

Each node in a CAN bus can both send and receive a variety of messages across the network. The major components are:

  • Start-of-frame (1 bit). This tells nodes that a message is incoming.
  • Identifier (11 bits). This says where the message is coming from. Lower values have a higher priority (temperature, RPMs).
  • Remote Transmission Request (1 bit). Allows nodes to request information from other nodes.
  • Data Length Code (4 bits). Tells nodes how much data is being transmitted.
  • Data (0-8 bytes) (0-64 bits). The actual data transmitted.
  • Cycle Redundancy Check (15 bits). Used to ensure the data isn’t corrupted.
  • Acknowledgment (1 bit). Indicates that the cycle redundancy check was successful.
  • End of Frame (7 bits). Marks the end of the message.

Crunching CAN bus data in T3

As you can see, there’s a lot of data included in each CAN bus message. But in a raw format, these messages don’t make much sense at all. Every machine has its own CAN messaging idiosyncrasies that, to most people, just look like a bunch of random numbers and letters.

That’s where an operating system like T3 comes in. T3 digests the raw CAN bus data into actionable reports on your equipment. Our engineers have worked hard to make sure our operating system understands CAN bus data from a wide range of vehicles and assets. The end result is that you get lots of in-depth information about your fleet — things like runtime, engine temperature and oil status. You can quickly and easily run diagnostics on any machine from anywhere, identifying potential problems and improving overall machine health. This, in turn, leads to better overall fleet efficiency and more profitability.

And it all starts with the small but complex system known as the CAN bus.

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Telematics, Technology