Circuit: A DIY CAN Tester

Want to conduct experiments and tests on a CAN bus? You can with this DIY CAN tester design from 2013, which also offers the option of connecting an existing CAN bus to monitor the data or to track down faults.

CAN Tester Circuit 

The CAN Tester design features two identical circuit boards (board A and board B), which are loaded with different software. You can equip each board with a 4 × 20 LCD. The boards communicate with in accordance with the CAN protocol, and they can also be connected to an existing CAN bus.
  The circuit consists of several key components:
 

• An ATmega8515 8-bit microcontroller (IC1)
• An SJA1000 CAN protocol controller (IC4)
• A PCA82C250 CAN transceiver (IC3)
• MAX232: RS-232 transceiver (IC2, for communication with the PC)
• A 4 × 20 character LCD (LCD1)

"The SJA1000 is a bitstream processor with a transmit and receive buffer," Hugo Stiers explained. "This is controlled and initialized by the ATmega8515. The ATmega8515 provides the transmit buffer of the SJA1000 with messages and reads out the receive buffer. The SJA1000 is connected to the ATmega8515 via a multiplexed address/data bus (PA0 – PA7). In addition, there are four control signals that go to the SJA1000: CS (chip select), ALE (address latch enable), RD (read) and WR (write)."
 

Once constructed, the CAN Tester offers the following:
 

• Test configuration with boards A and B, for 29-bit and/or 11-bit IDs (automatic)
• Reading out of CAN data on the LCD (for example parking brake, odometer reading, etc.)
• Reading out of CAN data on the LCD (for Examine data using HyperTerminal
• Test functionality with pushbuttons and LEDs
• Simulation of messages

Applications

In the article, Stiers describes a few different applications.
 

• Application 1: Board A and board B send and receive messages automatically to each other
• Application 2: Single CAN Tester with LCD (handbrake, odometer reading, etc.)
• Application 3: Viewing data using Hyper-Terminal (baud rate = 57,600)
• Application 4: CAN Tester with pushbuttons and LEDs
• Application 5: The CAN Tester as a simulator for messages

The CAN Tester and More

Hugo Stiers's article, "CAN Tester with Comprehensive Features" appeared in Elektor November 2013, which Elektor Members can download immediately. Member benefits include: a subscription to ElektorMag, a 10% Elektor Store discount on many products, and full access to our online library. If you would like an Elektor membership, sign up today.

Editor's Note: This article was originally published in a previous edition of Elektor. Some of the products or PCBs may no longer be available in our store or elsewhere. However, we think the educational content remains valuable and hope it inspires you to embark on new and exciting projects.