High-Speed Controller Area Network (CAN) Basics

If the High-Speed Controller Area Network (CAN) is something you don’t deal with often, here are a few basics to refresh your memory.

Controller Area Network (CAN)

• Standard protocol for communication between vehicle control systems.
• Developed because vehicles have increasing numbers of electronic control systems that require communication between individual control units.
• CAN control units are connected in parallel (e.g., ECU, TCU, ADAS^*, and ESC^*) and upload their data to the network (or BUS) so it can be shared with other control units that need this data.
• Key Advantages
  • Simple structure capable of fast communication
  • Requires less wiring and lowers vehicle weight
  • Provides efficient system control
  • Reduced cost
  • Ease of adding and controlling different devices on the CAN bus
  • Twisted-pair wiring is highly tolerant to electrical noise, so data is protected

Wiring Basics

CAN Wiring

• Twisted pair wiring
• Tolerant to electrical noise

Terminating Resistors

• 120 Ω each
• At the ends of each network
• Prevents reflective signal waves and stabilizes voltage signal

Communication Waveform

• There are two signals: CAN High and CAN Low
• These two signals have opposite phases (binary data)

Waveform Scope Pattern

• CAN High rises to 3.5 V from 2.5 V
• CAN Low drops to 1.5 V from 2.5 V
• Voltage level is used as a data communication language
• Binary numbers for this language are translated by measuring the output voltage differences

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