Time synchronization using PTP

Introducing how to use PTP(Precision Time Protocol) in distributed systems like robot system. Here we will introduce a method to synchronize the time between two systems within the robot system. (여기서 로봇 시스템 내에 있는 두 시스템간의 시간을 동기화 하는 방법을 소개할 것이다.)

the difference between ptpd <--> ptp4l

This Article deal with ptpd

ptp4l vs ptpd

Install ptpd

$ sudo apt install ptpd

Check your Network interface

$ ethtool -T eno1
...
Time stamping parameters for eno1:
Capabilities:
    hardware-transmit     (SOF_TIMESTAMPING_TX_HARDWARE)
    software-transmit     (SOF_TIMESTAMPING_TX_SOFTWARE)
    hardware-receive      (SOF_TIMESTAMPING_RX_HARDWARE)
    software-receive      (SOF_TIMESTAMPING_RX_SOFTWARE)
    software-system-clock (SOF_TIMESTAMPING_SOFTWARE)
    hardware-raw-clock    (SOF_TIMESTAMPING_RAW_HARDWARE)
...

The following properties should be found

SOF_TIMESTAMPING_RAW_HARDWARE
SOF_TIMESTAMPING_TX_HARDWARE
SOF_TIMESTAMPING_RX_HARDWARE

Set up through command line

Set up the master

$ sudo ptpd -V -i enp89s0 -M -L

Set up the slave

$ sudo ptpd -V -i eno1 -s -L

Set up through the configuration file

Default File config

The following is the default config file after installing ptpd.

# /etc/default/ptpd
# Set to "yes" to actually start ptpd automatically
START_DAEMON=no
# Add command line options for ptpd
PTPD_OPTS=""

Set up the master system

/etc/default/ptpd

# /etc/default/ptpd

# Set to "yes" to actually start ptpd automatically
START_DAEMON=yes

# Add command line options for ptpd
PTPD_OPTS="-c /etc/ptpd.conf"

/etc/ptpd.conf

; /etc/ptpd.conf
; This is configuration for master
ptpengine:interface=enp89s0
ptpengine:preset=masteronly
 
ptpengine:log_announce_interval=-1
ptpengine:log_announce_interval_max=0
ptpengine:log_sync_interval=-1
ptpengine:log_sync_interval_max=0
ptpengine:clock_update_timeout=1  

Set up the slave system

/etc/default/ptpd

# /etc/default/ptpd

# Set to "yes" to actually start ptpd automatically
START_DAEMON=yes

# Add command line options for ptpd
PTPD_OPTS="-c /etc/ptpd.conf"

/etc/ptpd.conf

; /etc/ptpd.conf                      
; This is configuration for slave     
ptpengine:interface=eno1              
ptpengine:preset=slaveonly            
                                        
ptpengine:log_announce_interval=-1    
ptpengine:log_announce_interval_max=0 
ptpengine:log_sync_interval=-1        
ptpengine:log_sync_interval_max=0     
ptpengine:clock_update_timeout=1    

Restart ptp system daemon

restart the master & slave

$ sudo systemctl restart ptpd.service
$ sudo systemctl status ptpd.service
● ptpd.service - LSB: start and stop ptpd
     Loaded: loaded (/etc/init.d/ptpd; generated)
     Active: active (running) since Tue 2024-02-20 09:34:14 KST; 4s ago
       Docs: man:systemd-sysv-generator(8)
    Process: 6632 ExecStart=/etc/init.d/ptpd start (code=exited, status=0/SUCCESS)
      Tasks: 1 (limit: 9274)
     Memory: 1.1M
     CGroup: /system.slice/ptpd.service
             └─6639 /usr/sbin/ptpd -c /etc/ptpd.conf

Feb 20 09:34:14 FORMER-0024 ptpd2[6638]: Starting ptpd2 daemon with parameters:      /usr/sbin/ptpd -c /etc/ptpd.conf
Feb 20 09:34:14 FORMER-0024 ptpd2[6638]: Loading configuration file: /etc/ptpd.conf
Feb 20 09:34:14 FORMER-0024 ptpd2[6638]: Checking configuration
Feb 20 09:34:14 FORMER-0024 ptpd2[6638]: Configuration OK
Feb 20 09:34:14 FORMER-0024 ptpd2[6638]: Successfully acquired lock on /var/run/ptpd2.lock
Feb 20 09:34:14 FORMER-0024 ptpd2[6639]:   Info:    Now running as a daemon
Feb 20 09:34:14 FORMER-0024 ptpd2[6639]: Successfully acquired lock on /var/run/ptpd2.lock
Feb 20 09:34:14 FORMER-0024 systemd[1]: Started LSB: start and stop ptpd.
Feb 20 09:34:14 FORMER-0024 ptpd2[6639]: PTPDv2 started successfully on eno1 using "slaveonly" preset (PID 6639)
Feb 20 09:34:14 FORMER-0024 ptpd2[6639]: TimingService.PTP0: PTP service init

References

Example of the ptpd config file

https://gist.github.com/mhaberler/f4809ed2e465912d3534