N109X-Series Osciloscope with N1076/7A

This Python example uses an N109X-series DCA-M oscilloscope and N1076/7A clock recovery to perform an eye measurement (bit rate) on channel 6A. It is the same as N109X-Series Osciloscope example, but adds clock recovery. The programs performs the following tasks:

Places FlexDCA to its default settings. This places the FlexDCA triggering to front panel which is required to view a valid eye diagram.
Configures the clock recovery.
Configures N109X.
Queries the N109X to see if it supports pattern locking (option PLK) and then turns on pattern locking if available.
Returns the measured trigger rate that is input to the N109X.
Runs an acquisition limit test and then activates the bit-rate measurement on the data.

About the :TRIGger:MRATe? query

The :TRIGger:MRATe? query returns the baud rate of the N109X’s clock input signal. For this query to work, at least one of the N109X’s input channels must be turned on, but a signal does not need to be connected to the channel. Also, the N109X’s data acquisition must be in Run mode, or, if in single mode, a single acquisition must first be run to ensure valid data for the measurement.

To run this program

Run this program on a PC that has FlexDCA running. In the following program listing, FlexDCA is identified by the red text: localhost.
If you change localhost to an N1000A, you can run the program on a PC to control FlexDCA on an N1000A. Connect the N109X to the N1000A.
Install an N109X-series oscilloscope to FlexDCA’s slot 6. Change the DCAMSLT constant if you want to use a different slot.
Install an N1076/7A clock recovery to FlexDCA’s slot 5. Change the RECSLT constant if you want to use a different slot.
Data in is expected to be 10.3125 GBd, but you can change this to any acceptable rate for the oscilloscope.
Connect valid signal to channel 6A on the N1090X.
Connect a clock to the N1090X’s Clock In.
Display an eye diagram on FlexDCA.

Example Script

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DCA-M-eye-meas-N107X.py

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# -*- coding: utf-8 -*-
""" Demonstrates using a DCA-M oscilloscope with N107x-series clock
recovery to make a bit-rate eye measurement. Requires:
N109X-series DCA-M oscilloscope in slot 6. N1076/7A in slot 5.
Change the N107X_SLOT and N109X_SLOT constants if you want to use
different slots.
Runs on a PC that is controlling an N109X / N1076/7A that are
connected to the PC.
Edit "localhost" in address to a DCA-X if the N109x is connected to an
DCA-X.
Data in is expected to be 10.3125 Gb/s Data In, but you can change this
to any acceptable rate for the oscilloscope in the DRATE constant.
The default setup command places the DCA-X and DCA-M triggering to front
panel which is required to view a valid eye diagram.
"""

import pyvisa as visa  # import VISA library

visa_address = 'TCPIP0::localhost::hislip0,4880::INSTR'
ADDRESS = 'TCPIP0::localhost::hislip0,4880::INSTR'
N107X_SLOT = '5'  # N1077A's slot
N109X_SLOT = '6'  # N1092D's slot
DRATE = '10.312500E+9'  # input data rate


def open_flexdca_connection(address):
    """ Opens visa connection to FlexFlexDCA. """
    try:
        rm = visa.ResourceManager()
        connection = rm.open_resource(address)
        connection.timeout = 20000  # Set connection timeout to 20s
        connection.read_termination = '\n'
        connection.write_termination = '\n'
        inst_id = connection.query('*IDN?')
        print('\nFlexDCA connection established to:\n' + inst_id, flush=True)
        connection.write(':SYSTem:DEFault')
        connection.query('*OPC?')
    except (visa.VisaIOError, visa.InvalidSession):
        print('\nVISA ERROR: Cannot open instrument address.\n', flush=True)
        return None
    except Exception as other:
        print('\nVISA ERROR: Cannot connect to instrument:', other, flush=True)
        print('\n')
        return None
    return connection


def all_channels_off(FlexDCA):
    """ Turns all available channels off. """
    for slot in '12345678':
        for letter in 'ABCD':
            channel = slot + letter
            FlexDCA.write(':CHANnel' + channel + ':DISPlay OFF')


def setup(FlexDCA, N109X_SLOT, N107X_SLOT):
    # Default all settings. Set trigger and turn on channel.
    FlexDCA.query(':SYSTem:DEFault;*OPC?')
    FlexDCA.write(':TRIGger:SOURce FPANel')
    all_channels_off(FlexDCA)
    FlexDCA.write(':CHAN'+N109X_SLOT+'A:DISPlay ON')  # Turn channel 'A' on
    # Configure N1077A clock recovery.
    FlexDCA.write(':CRECovery' + N107X_SLOT +
                  ':SOURce ELECtrical')  # set input type
    FlexDCA.write(':CRECovery' + N107X_SLOT +
                  ':CRATe ' + DRATE)  # set input data rate
    FlexDCA.write(':CRECovery' + N107X_SLOT +
                  ':CLBandwidth 5.692E+6')  # set PLL loop BW
    FlexDCA.query(':CRECovery' + N107X_SLOT + ':RELock;*OPC?')


def setup_dcam(FlexDCA, N109X_SLOT):
    """ Configure DCA-M and query measured clock input rate."""
    FlexDCA.write(':ACQuire:SINGle')
    clockrate = FlexDCA.query(':SLOT'+N109X_SLOT+':TRIG:MRATe?')
    if '-1.00' in clockrate or '0.00' in clockrate:
        print('DCA-M is not triggered. Check inputs.')
        return False
    FlexDCA.query(':ACQ:RUN;*OPC?')
    FlexDCA.query(':SYSTem:MODE EYE;*OPC?')
    return True


def pattern_lock(FlexDCA, N109X_SLOT, DRATE):
    """ If DCA-M pattern lock option is installed, configure acquisition
    test to acquire pattern waveforms. """
    if 'PLK' in FlexDCA.query(':SYST:OPTions? SLOT'+N109X_SLOT):
        FlexDCA.write(':TRIGger:BRATe:AUTodetect OFF')
        FlexDCA.write(':TIMebase:BRATe ' + DRATE)
        FlexDCA.write(':SLOT'+N109X_SLOT+':TRIGger:TRACking ON')
        FlexDCA.query(':TRIGger:PLOCk ON;*OPC?')
        print('Pattern lock on.')
        return True
    return False


def make_measurement(patternlock):
    """ Perform acquisition limit test and bit-rate measurement. """
    FlexDCA.query(':AUToscale;*OPC?')
    FlexDCA.write(':ACQuire:STOP;:ACQuire:CDISplay')
    if patternlock:
        FlexDCA.write(':LTESt:ACQuire:CTYPe:PATTerns 1')
    else:
        FlexDCA.write(':LTESt:ACQuire:CTYPe:WAVeforms 100')
    FlexDCA.write(':LTESt:ACQuire:STATe ON')
    FlexDCA.query(':ACQuire:RUN;*OPC?')
    FlexDCA.write(':LTESt:ACQuire:STATe OFF')
    FlexDCA.write(':MEASure:EYE:BITRate')
    print('Measured:')
    print('  Eye Bit Rate: ' + FlexDCA.query(':MEASure:EYE:BITRate?') + ' b/s')
    print('  Clock rate: ' + FlexDCA.query(':SLOT'+N109X_SLOT+':TRIG:MRATe?') +
          ' baud (Bd)')


FlexDCA = open_flexdca_connection(visa_address)
setup(FlexDCA, N109X_SLOT, N107X_SLOT)
if setup_dcam(FlexDCA, N109X_SLOT):
    make_measurement(pattern_lock(FlexDCA, N109X_SLOT, DRATE))
FlexDCA.write(':SYSTem:GTLocal')
FlexDCA.close()