# CAN bus: controller, transceiver and termination

Separate the MCU's CAN signals from the two-wire physical bus.

**Applies to:** Conventional high-speed two-wire CAN. This is not a low-speed fault-tolerant, single-wire, OBD connector or automotive harness pinout.

## When to use it

Building a documented CAN network between development boards, robots or instruments.

## Why it works this way

CAN controllers handle messages and arbitration; transceivers connect those controllers to CANH/CANL.

![CAN bus: controller, transceiver and termination — Conventional high-speed two-wire CAN. This is not a low-speed fault-tolerant, single-wire, OBD connector or automotive harness pinout.](https://valleytech-black-wire-guide.pages.dev/library/wiring/can-bus.svg)

[Open / save the original SVG](https://valleytech-black-wire-guide.pages.dev/library/wiring/can-bus.svg)

## Connection reference

| Connection | Meaning | Check |
| --- | --- | --- |
| MCU TX / RX | Controller-to-transceiver logic | I/O supply compatibility |
| CANH / CANL | Twisted differential pair | Do not swap or attach directly to GPIO |
| 120 ohm at each end | End termination | Include terminators already fitted |
| Reference / isolation | Keep common-mode within limits | Follow the transceiver and system design |

## Make the connection

1. Keep the trunk linear and stubs short; choose cable length and rate together.
2. Match bit timing; CAN FD needs compatible controllers and transceivers.
3. Use another active receiving node for acknowledgement during a normal transmit test.

## Check before powering

- CAN does not define one universal connector or wire-color scheme.
- With all power removed, two simple 120-ohm end resistors in parallel give about 60 ohms; this check alone cannot prove correct wiring.

## Matching module references

This is a general interface guide; match your own hardware documentation.

## Sources & review

Source documents inspected; independent electrical and bench review pending. Reviewed 2026-09-27.

- [Texas Instruments: CAN physical layer, SLLA270](https://www.ti.com/lit/an/slla270/slla270.pdf) — Figures 6, 8 and 9: transceivers and end termination; connector scope; checked 2026-09-27

Original writing and diagram by Kal / Valleytech Solutions, CC BY 4.0. Manufacturer artwork and documentation retain their own rights.

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