In previous articles, we have looked at what CANBus is and why we use it, and how it appears electrically. To work with CANBus we need hardware that can convert the electrical pulses into something a microprocessor can understand, 0’s and 1’s. In this article, we will look at the CANBus adapter and its purpose.
Converting pulses to information
All devices that connect to a CANBus need a CAN Transceiver, such as the MCP2551. This will convert received analogue pulses to binary signals, and to convert binary into outgoing pulses. A CAN Controller, such as the MCP2515, is also required to convert the continuous flow of binary signals from the CAN transceiver into data. The CAN Controller breaks down the incoming data into messages. It can also build a CAN frame based on data given to it. In a later article, we will look at CAN frames, their structure and how they are formed.
Professional CANBus Adapters
One of the first steps to working with CAN is to see it so really we want a way to connect a PC to an existing CANBus and start seeing messages!
In the automotive sector, CANBus adapters range in price from £600 to £10,000’s and usually require licenses to work with industry-standard software. In the picture above we have three entry-level automotive sector adapters.
On the left is the PEAK CAN-USB which costs around £170, comes with some very basic software and is one of the easiest devices to program for. It has a single high speed CAN channel which quickly becomes a limiting factor when looking at multiple CANBus simultaneously.
In the middle is the ETAS ES581 which costs around £600, has dual channels and is intended for use with the ETAS INCA software chain. ETAS software licenses are many £1000s each. ETAS hardware and software is extensively used in engine management development. I’ve always found the basic ETAS USB adapters to be a bit of a fiddle to get the drivers working once you move away from Windows 7. This may have improved with the latest variant of the ES582.
Finally, on the right of the image, the VECTOR VN1610 which again costs around £600. This adapter has dual channels, it is intended for use with the VECTOR software family including CANoe, CANalyzer and CANape. Like the ETAS, software licenses are prohibitively expensive for home hobbyists. VECTOR hardware can be a little tricky to program for, but once you get the hang of it the hardware gives the most reliable results.
Software for interpreting CANBus data?
These three adapters are the ones I’ve used the most in my career. They are however just about in the reach of a committed hobbyist. The professional software licenses, however, are prohibitively expensive. So why would I propose any of them? Well, all three of these CANBus adapters work with a piece of free software called BusMaster. In the next article, we’ll look at how we can use the software to interpret CANBus data.