This content originally appeared on DEV Community and was authored by DEBIX Industrial Computers
Test Environment:
LinuxDevelopment Environment: Yocto 5.0（scarthgap）
U-Boot: U-Boot 2024.04
Kernel: Linux-6.6.36
Linux SDK: L6.6.36-2.1.0
Version: Debix SOM A V1.01_20241024
Devices: 2 * DEBIX SOM A + DEBIX SOM A IO Board
Test Steps:
Power on and run 2 pcs of mainboards, then enter the device console.
Run DebixVersion to check the basic information of the device.
Connect the ETH1 interfaces of the two DEBIX SOM A IO Boards using an Ethernet cable (only ETH1 supports TSN, you can check with the command ethtool -T ens33).
On the master device console, run:
ptp4l -E -4 -H -i ens33 -l 6 -m -q -f /etc/linuxptp/ptp4l.conf
On the slave device console, run:
ptp4l -E -4 -H -i ens33 -s -l 6 -m -q -f /etc/linuxptp/ptp4l.conf
Check the printed log information.
The log shows that the slave device synchronizes with the external master clock 100723.fffe.6df691-1, which corresponds to the master device’s ETH1 port.
Once the test stabilizes, review the data.
Example of the last log entry:
ptp4l[882.689]: master offset 12 s2 freq -8638 path delay 747
ptp4l[882.689]
ptp4l: This is the core daemon implementing the PTP (Precision Time Protocol) on Linux. PTP, also known as IEEE 1588, is a high-precision time synchronization protocol designed to provide sub-microsecond synchronization for devices within a LAN.
[882.689]: Process runtime timestamp in seconds, showing elapsed time since the process started.
master offset: 12
Meaning: The time difference between the local clock (slave) and the remote master clock.
Unit: Nanoseconds (ns).
Interpretation: 12 means the local clock lags behind the master clock by 12 ns. This is extremely precise synchronization (1 second = 1,000,000,000 ns).
s2 freq: -8638
Meaning: The frequency adjustment value calculated by ptp4l to correct clock offset in slave state. s2 refers to the slave state of ptp4l.
Unit: Parts per billion (ppb). This value will be passed to phc2sys (used to synchronize the system clock and hardware clock) or directly to the Linux kernel clock discipline.
Interpretation: -8638 means the local oscillator frequency is reduced by 8638 ppb to catch up with the master. This relatively large adjustment indicates the local clock was initially faster.
path delay: 747
Meaning: The round-trip delay between slave and master.
Unit: Nanoseconds (ns).
Interpretation: 747 ns is very low, suggesting excellent network hardware performance (likely hardware timestamping support). In software-timestamped networks, this value is usually tens to hundreds of microseconds.
Explanation of Test Command Parameters
This content originally appeared on DEV Community and was authored by DEBIX Industrial Computers
DEBIX Industrial Computers | Sciencx (2025-09-15T09:59:18+00:00) DEBIX SOM A Testing TSN Clock Synchronization with PTP. Retrieved from https://www.scien.cx/2025/09/15/debix-som-a-testing-tsn-clock-synchronization-with-ptp/
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