getTimeLastPPS

Radio time of last pulse per second signal

Since R2025a

Add-On Required: This feature requires the Wireless Testbench™ Support Package for NI™ USRP™ Radios add-on.

Syntax

tLastPPS = getTimeLastPPS(radio)

Description

tLastPPS = getTimeLastPPS(radio) returns the time that the last pulse per second (PPS) signal occurred on the radio associated with the radio object radio.

Examples

Reset Radio Time on Next PPS Signal

Create a radio object, specifying a radio setup configuration previously saved using the Radio Setup wizard.

radio = radioConfigurations("MyRadio");

Get the current radio time in seconds from the time registers on the radio. This function connects to the radio and resets the radio time.

getRadioTime(radio)

ans = 
0.0423

Wait 5 seconds, then get the time that the last PPS signal occurred.

pause(5)
tLastPPS = getTimeLastPPS(radio)

tLastPPS = 
4.4874

When a PPS signal occurs, reset the radio time to zero.

setTimeNextPPS(radio,0);

Wait 1 second, then get the current radio time to confirm that the radio time has been reset.

pause(1)
getRadioTime(radio)

ans = 
0.6839

Since the radio time is less than 1 second, the radio time has been successfully reset.

Synchronize Radio Time on Multiple Radios

Synchronize the radio time on two NI USRP radios that share a clock and time source.

Create Radio Objects

Create a radio object for each radio, specifying a radio setup configuration previously saved using the Radio Setup wizard.

radio1 = radioConfigurations("MyRadio")

radio1 = 
  N320 with properties:

           Name: "MyRadio"
       Hardware: "USRP N320"

      IPAddress: "192.168.20.2"

    ClockSource: "external"
     TimeSource: "external"

       LOSource: "internal"

radio2 = radioConfigurations("MyRadio2")

radio2 = 
  N321 with properties:

             Name: "MyRadio2"
         Hardware: "USRP N321"

        IPAddress: "192.168.21.2"

      ClockSource: "external"
       TimeSource: "external"

         LOSource: "internal"
       LOExported: 0
    LODistributed: 0

Create and Configure Application Object or usrp System Object

After you create your radio objects and before you synchronize the radio time, you should fully configure your radio. Connecting to the radio to load an application or update an RF property resets the radio time.

To configure one or both of your radios using a baseband or detector application object, use the corresponding radio object as the radio input argument when you create the object. Additionally, specify the Preload name-value argument as true and specify all RF properties using the PropertyName=Value syntax. The commented code shows an example.

% bbtrx = basebandTransceiver(radio, ...
%     Preload=true, ...
%     TransmitDataType="double", ...
%     TransmitAntennas="RFA:TX/RX", ...
%     TransmitCenterFrequency=2.4e9, ...
%     TransmitRadioGain=10, ...
%     CaptureAntennas="RFA:RX2", ...
%     CaptureCenterFrequency=2.4e9, ...
%     CaptureRadioGain=10);

To connect to and control one or both of your radios with a custom FPGA image that you created by using the Target NI USRP Radios Workflow, use the corresponding radio object as the radio input argument when you create a usrp System object. Then, run all the code required to configure your radio, your DUT, and the interfaces between them, up to the point where you call the setup function on your usrp System object. The commented code shows an example.

% device = usrp(radio, ...
%     SampleRate=250e6, ...
%     TransmitAntennas="DB0:RF0:TX/RX0", ...
%     TransmitDDRAllocation=1000);
% programFPGA(device,"myBitstream.bit","myDeviceTree.dts");
% describeFPGA(device,"ModelName_wthandoffinfo.mat"); 
% dut = fpga(device);
% addRFNoCRegisterInterface(dut, ...
%     "InterfaceID","DUTName", ...
%     "RFNoCBlock","0/DUTName#0");
% DUTPort_Read_Register = hdlcoder.DUTPort("Read_Register", ...
%     "Direction","OUT", ...
%     "DataType","int16", ...
%     "IsComplex",false, ...
%     "Dimension",[1 1], ...
%     "IOInterface","DUTName", ...
%     "IOInterfaceMapping",1);
% mapPort(dut,DUTPort_Read_Register);
% setup(device);

You can now proceed to synchronize the radio time.

Synchronize Radio Time

To synchronize both radios to use a common radio time, set the radio time on both radios to the same value on the next PPS signal. First, use the getTimeLastPPS function to get the time that the last PPS occurred.

tLastPPS = getTimeLastPPS(radio1);

When a PPS signal is detected, you have one second to set a new radio time. Check for a new signal every 0.1 seconds, then use the setTimeNextPPS function to set the radio time on both radios to zero.

while tLastPPS == getTimeLastPPS(radio1)
    pause(0.1)
end
setTimeNextPPS(radio1,0);
setTimeNextPPS(radio2,0);

To verify that the radio time is synchronized, verify that the last PPS signal occurred at the same time on both radios.

pause(1.1)
tLastPPS1 = getTimeLastPPS(radio1);
tLastPPS2 = getTimeLastPPS(radio2);
isequal(tLastPPS1,tLastPPS2)

ans = logical
   0

If the radio time synchronization is unsuccessful, try running this code section again.

Input Arguments

radio — Radio object

radio object

Radio object, specified as a radio object that corresponds to a radio setup configuration you saved using the Radio Setup wizard.

To create a radio object, call the radioConfigurations function with the name of your radio setup configuration. For example, for a radio setup configuration named MyRadio, call radio = radioConfigurations("MyRadio").

Output Arguments

tLastPPS — Radio time that last PPS signal occurred in seconds

positive numeric scalar

The radio time that the last PPS signal occurred in seconds, returned as a positive numeric scalar.

For more information about radio time, see Radio Time.

Data Types: double

Version History

Introduced in R2025a