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Time synchronization

Table of Contents

Introduction

This README gives an introduction to the C++ and Python code examples in this folder. The document describes how to synchronize the device time via two methods:

  • Network time protocol (NTP)

  • Precision time protocol (PTP)

Note

Note: These samples only work for Sick Visionary-T Mini CX (V3S105-1x). Visionary-S CX (V3S102-1x) is not supported.

How to run the samples

Run the NTP sample

You will find the sample code in time_synchronization/cpp/ntp_sync.cpp and time_synchronization/python/ntp_sync.py respectively. Make sure you fullfill all NTP Prerequistes before continuing to run the sample.

Either build and run the samples from the top level directory as described in Getting Started or build and run the samples from the sample subdirectory using its CmakeLists.txt file.

Note

Remember to adjust the command line arguments like IP address (-i), server IP address (-s), server port (-p), server timeout (-t) to match your specific setup.

C++

# From toplevel dir
./time_synchronization/cpp/build/ntp_sync -i192.168.1.10 -s192.168.136.100 -p123 -t5000

# From time_synchronization/cpp directory
./build/ntp_sync -i192.168.1.10 -s192.168.136.100 -p123

Python

# From toplevel dir
python time_synchronization/python/ntp_sync.py -i192.168.1.10 -s192.168.136.100 -p123

Run the PTP sample

You will find the sample code in time_synchronization/cpp/ptp_sync.cpp and time_synchronization/python/ptp_sync.py respectively. Make sure you fullfill all PTP Prerequistes before continuing to run the sample.

Either build and run the samples from the top level directory as described in Getting Started or build and run the samples from the sample subdirectory using its CmakeLists.txt file.

Note

Remember to adjust the command line argument IP address (-i) to match your specific setup.

C++

# From toplevel dir
./time_synchronization/cpp/build/ptp_sync -i192.168.1.10

# From time_synchronization/cpp directory
./build/ptp_sync -i192.168.1.10

Python

# From toplevel dir
python time_synchronization/python/ptp_sync.py -i192.168.1.10

Network time protocol (NTP)

Network Time Protocol (NTP) is a networking protocol used to synchronize the clocks of computers over a network. It ensures that all participating devices have the same time, which is crucial for time-sensitive applications and processes. NTP operates by exchanging time-stamped messages between a client and a server, allowing the client to adjust its clock based on the server’s accurate time. This protocol can achieve synchronization within milliseconds over the internet and even better accuracy in local networks.

NTP Prerequistes

You need a running NTP server for this sample to work. We advice using a UNIX based system and running the standard NTP-daemon on it. Make sure the NTP server has a low stratum number, either by synchronizing it with an online NTP server or by manually setting the stratum number inside /etc/ntp.conf like this:

cat /etc/ntp.conf

# Needed if the device is itself not synchronizing to an online NTP server
# This specifies that the device functions as a stratum 2 server
server 127.127.1.0
fudge 127.127.1.0 stratum 2

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery limited
restrict -6 default kod notrap nomodify nopeer noquery limited
restrict 192.168.136.0 mask 255.255.255.0 #if the device is in this subnet

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict ::1

For more information have a look at ConfiguringNTP.

After configuring run these commands:

sudo service ntp status
sudo service ntp restart
# or
sudo service ntp stop
sudo service ntp start

Now you should be able to synchronize the camera with the NTP server.

Explanation

This section opens a control channel to the device.

device_control = Control(ip_address, cola_protocol, control_port)
    device_control.open()

Login to the device to gain access rights to certain methods (the examples uses the default credentials).

# Login to the device for access rights to certain methods
        device_control.login(Control.USERLEVEL_SERVICE, 'CUST_SERV')

Retrieve the device’s current time before synchronization.

device_timestamp_ms = device_control.getDeviceTime()
    device_time = datetime.fromtimestamp(device_timestamp_ms/1000, tz=timezone.utc).strftime('%Y-%m-%d %H:%M:%S')
    print(f"Device time before time synchronization: {device_time}")

Make sure your NTP server is running and connected to the subnet. Enter 'Y' to proceed.

# Ask user about NTP Master
    print("Running NTP Master is connected to the network? [Y/N]")
    user_input = input().strip().upper()

Set the IP address of the NTP server.

device_control.setNtpClientServerAddress(server_ip)
        print(f"Set NTP server IP: {server_ip}")

Set the port number for the NTP server (default is 123).

device_control.setNtpClientServerPort(ntp_port) # default is 123
        print(f"Set NTP port: {ntp_port}")

Set the timeout for NTP requests.

device_control.setNtpClientTimeout(timeout)
        print(f"Set NTP request timeout: {timeout}")

Enable NTP time synchronization on the device. The device should send out an NTP synchronization request to the server as soon as this variable gets enabled.

device_control.setTimeSyncMode('NTP')
        print("Enabled NTP time synchronization")

We wait for 5 seconds to ensure synchronization is complete. If there’s a working NTP server in the subnet this synchronization should finish immediately.

time.sleep(5)
        print("Waiting for 5 seconds to be on the safe side.")

Retrieve the device’s time after synchronization.

device_timestamp_ms = device_control.getDeviceTime()
        device_time = datetime.fromtimestamp(device_timestamp_ms/1000, tz=timezone.utc).strftime('%Y-%m-%d %H:%M:%S')
        print(f"Device time after time synchronization: {device_time}")

Reset settings by disabling NTP time synchronization.

device_control.setTimeSyncMode('NONE')
    print("Disabled NTP time synchronization")

Logout from the device and close the control channel.

device_control.logout()
    device_control.close()
    print("Logged out. Closed connection.")

Precision time protocol (PTP)

Precision Time Protocol (PTP) is a protocol used to synchronize clocks throughout a computer network. It is designed for systems requiring high precision time synchronization, such as industrial automation, telecommunications, and financial trading systems. PTP achieves synchronization by exchanging timing messages between a master clock and slave clocks, allowing the slave clocks to adjust their time to match the master clock with sub-microsecond accuracy. This protocol is particularly useful in environments where precise timing is critical for performance and reliability.

PTP Prerequistes

To run this sample, you need a functioning PTP master. We recommend using a UNIX-based system and running ptpd — an open-source implementation of the Precision Time Protocol (PTP).

Run the following command to start a PTP Master with the options:

-M: Enables master mode. -i eth0: Specifies the network interface to use (e.g., eth0). -V: Enables verbose output for debugging and monitoring.

sudo ptpd -M -i YOUR_INTERFACE -V

Explanation

This section opens a control channel to the device.

device_control = Control(ip_address, cola_protocol, control_port)
    device_control.open()

Login to the device to gain access rights to certain methods.

device_control.login(Control.USERLEVEL_SERVICE, 'CUST_SERV')

Retrieve the device’s current time before synchronization.

device_timestamp_ms = device_control.getDeviceTime()
    device_time = datetime.fromtimestamp(device_timestamp_ms / 1000, tz=timezone.utc).strftime('%Y-%m-%d %H:%M:%S')
    print(f"Device time before time synchronization: {device_time}")

Make sure your PTP server is running and connected to the subnet. Enter 'Y' to proceed.

# Ask user about PTP Master
    print("Running PTP Master is connected to the network? [Y/N]")
    user_input = input().strip().upper()

Set the device to act as a PTP-Slave.

device_control.setPtpMode("SLAVE")
        print("Set PTP Mode: SLAVE")

Enable PTP time synchronization on the device. The device should send out an PTP synchronization request to the PTP-Master as soon as this variable gets enabled.

device_control.setTimeSyncMode('PTP')
        print("Enabled PTP time synchronization")

We wait for 5 seconds to ensure synchronization is complete. If there’s a working PTP master in the subnet this synchronization should finish immediately.

print("Waiting for 5 seconds to be on the safe side.")
        time.sleep(5)

Retrieve the device’s time after synchronization.

device_timestamp_ms = device_control.getDeviceTime()
        device_time = datetime.fromtimestamp(device_timestamp_ms/1000, tz=timezone.utc).strftime('%Y-%m-%d %H:%M:%S')
        print(f"Device time after time synchronization: {device_time}")

Reset settings by disabling PTP time synchronization.

device_control.login(Control.USERLEVEL_SERVICE, 'CUST_SERV')
    device_control.setTimeSyncMode('NONE')
    print("Disabled PTP (timeSyncMode)")

Logout from the device and close the control channel.

device_control.logout()
    device_control.close()