CAN Baud Rate Calculator

CAN / CAN FD Bit Timing Calculator

Target Settings

Basic Settings

Mode

CAN 2.0CAN FD

Clock (MHz)

Baud Rate

Arbitration Bit Rate (bps)

Sample Point Config

Arbitration Sample Point (%)

Tolerance Range

Baud Rate Tolerance (%)

Sample Point Tolerance (%)

Features

This tool supports bit time parameter calculation for Classic CAN and CAN FD modes, helping engineers quickly find the optimal configuration for target baud rate and sample point.

Input Parameters

Parameter	Description
Mode	Select Classic CAN or CAN FD mode
Clock (MHz)	Controller clock frequency (1-200 MHz)
Arbitration Baud	Arbitration phase target baud rate
Data Baud	Data phase target baud rate (CAN FD only)
Sample Point (%)	Target sample point position
Max Baud Error (%)	Baud rate error tolerance threshold
Max SP Error (%)	Sample point error threshold

Output Parameters

Parameter	Description
BRP	Baud Rate Prescaler
TSEG1	Time Segment 1 (Propagation Segment + Phase Segment 1)
TSEG2	Time Segment 2 (Phase Segment 2)
SJW	Synchronization Jump Width
Baud	Actual baud rate
Error (%)	Percentage error from target baud rate
Sample %	Actual sample point position
Tq (ns)	Time Quantum value in nanoseconds

Bit Time Basics

Bit Time Structure

CAN bus bit time consists of the following components:

Bit Time = 1 Tq (Sync_Seg) + TSEG1 + TSEG2

• Sync_Seg: Fixed at 1 Tq, used for synchronizing nodes on the bus
• TSEG1: Contains propagation segment and phase buffer segment 1, used to compensate for network delay and positive edge phase errors
• TSEG2: Phase buffer segment 2, used to compensate for negative edge phase errors

Sample Point Calculation

The sample point position determines when the bus level is sampled:

Sample Point (%) = (1 + TSEG1) / (1 + TSEG1 + TSEG2) × 100

Recommended Sample Points

Standard Protocol	Recommended Sample Point
CANopen	87.5%
DeviceNet	87.5%
ARINC 825	75% - 87.5%

Tip: The tool provides 70%, 75%, 80%, 85% quick options by default, and also supports manual input of other values.

Controller Parameter Ranges

The tool has built-in parameter ranges for two types of controllers:

Classic CAN (CAN 2.0)

Parameter	Range
BRP	1 - 64
TSEG1	1 - 16
TSEG2	1 - 8
SJW	max 4

CAN FD

Parameter	Range
BRP	1 - 512
TSEG1	2 - 256
TSEG2	1 - 128
SJW	max 128

CAN FD controllers have larger parameter ranges, supporting more flexible configurations.

CAN FD Dual-Phase Configuration

CAN FD uses two different baud rates within the same frame:

• Arbitration Phase: Uses standard baud rate, all nodes participate in arbitration
• Data Phase: Switches to high baud rate for data transmission after arbitration

Typical baud rate combinations:

Arbitration Phase	Data Phase	Switch Ratio
500 kbps	2 Mbps	4x
500 kbps	4 Mbps	8x
1 Mbps	2 Mbps	2x
1 Mbps	5 Mbps	5x

Export Formats

After selecting a configuration, it can be exported in three formats:

Param Format

Suitable for PCAN series device parameter configuration:

f_clock=80000000,nom_brp=10,nom_tseg1=13,nom_tseg2=2,nom_sjw=2

SocketCAN Format

Linux SocketCAN configuration command:

ip link set can0 up type can bitrate 500000 sample-point 0.875

CAN FD mode:

ip link set can0 up type can bitrate 500000 sample-point 0.875 dbitrate 2000000 dsample-point 0.750 fd on

JSON Format

Structured configuration data for program parsing:

{
  "mode": "canfd",
  "clock_mhz": 80,
  "arbitration": {
    "brp": 10,
    "tseg1": 13,
    "tseg2": 2,
    "sjw": 2,
    "baud": 500000,
    "sample_point": 87.5
  },
  "data_phase": {
    "brp": 4,
    "tseg1": 9,
    "tseg2": 2,
    "sjw": 2,
    "baud": 2000000,
    "sample_point": 83.3
  }
}

FAQ

Why can't I find a valid configuration?

Possible causes and solutions:

1. Inappropriate clock frequency: Try other common clocks (8/16/24/40/80 MHz)
2. Too strict error threshold: Appropriately relax baud rate or sample point error
3. Target baud rate too high/low: Check the match between clock and target baud rate

Actual baud rate differs from calculated value?

Investigation directions:

• Crystal frequency deviation from nominal value
• Clock source accuracy (recommended crystal with ±50ppm or better)
• Controller actual parameter range does not match tool settings

How to choose prescaler value?

Prescaler value affects Time Quantum (Tq):

• Smaller BRP → Smaller Tq → More precise time adjustment
• Larger BRP → Larger Tq → Larger time range

Usually choose BRP value that produces 8-25 Tq total bit time.

CAN FD data phase baud rate limit?

Limited by the following factors:

• Transceiver performance: Usually max 5-8 Mbps
• Bus length: Longer buses require lower baud rates
• Signal quality: Harsh environments need margin