Finding symbol sequences within a pattern waveform
This Python example, find_bit_sequence.py, demonstrates locating and displaying symbol sequences within a pattern waveform in Oscilloscope mode. Eacy instance of a symbol sequence is located within the waveform. A simulated module is installed.
Example Script
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find-bit-sequence.py
""" Script on PC controls FlexDCA or DCA-X from PC).
This script demonstrates locating and displaying symbol sequences
within a pattern waveform in Oscilloscope mode. The script opens
a connection to FlexDCA and installs a simulated module.
Requires a DCA-X with precision timebase option.
"""
import pyvisa as visa # import VISA library
ADDRESS = 'TCPIP0::localhost::hislip0,4880::INSTR'
#ADDRESS = 'TCPIP0::K-86100D-00003::hislip0,4880::INSTR' # DCA-X
CHANNEL = '5A'
def open_flexdca_connection(address):
""" Opens visa connection to FlexFlexDCA. """
print('Connecting to Flexdca ...')
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)
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 install_simulated_module(FlexDCA, channel, model, signal='NRZ'):
""" Simplified installation of a simulated FlexDCA module.
model is type of simulated module. "DEM" is a dual-electrical module.
"QEM" is a quad-electrical module. "DOM" is a dual-optical
module. "QEM" is a electrical-optical module.
signal if format of signal: NRZ or PAM4.
"""
slot = channel[0]
FlexDCA.write(':EMODules:SLOT' + slot + ':SELection ' + model)
if signal in 'NRZ':
FlexDCA.write(':SOURce' + channel + ':FORMat NRZ')
else:
FlexDCA.write(':SOURce' + channel + ':FORMat PAM4')
FlexDCA.write(':SOURce' + channel + ':DRATe 9.95328E+9')
FlexDCA.write(':SOURce' + channel + ':WTYPe DATA')
FlexDCA.write(':SOURce' + channel + ':PLENgth 127')
FlexDCA.write(':SOURce' + channel + ':AMPLitude 90E-3')
FlexDCA.write(':SOURce' + channel + ':NOISe:RN 3.0E-6')
FlexDCA.write(':SOURce' + channel + ':JITTer:RJ 4.0E-12')
FlexDCA.write(':CHANnel' + channel + ':DISPlay ON')
def setup(FlexDCA):
FlexDCA.query(':SYSTem:MODE OSCilloscope;*OPC?')
FlexDCA.query(':TRIGger:PLOCk ON;*OPC?')
FlexDCA.query(':SYSTem:AUToscale;*OPC?')
FlexDCA.write(':ACQuire:EPATtern ON')
FlexDCA.write(':ACQuire:RUN')
def view_entire_pattern(FlexDCA):
PatternLength = FlexDCA.query(':TRIGger:PLENgth?')
FlexDCA.write(':TIMebase:UIRange ' + PatternLength)
print('\nThe entire {0} symbol pattern is displayed.'
.format(PatternLength))
def waveform_acquisition(FlexDCA):
""" Performs waveform acquisition limit test. """
FlexDCA.write(':ACQuire:STOP') # single acquisition mode
FlexDCA.write(':ACQuire:CDISplay') # Clear display
FlexDCA.write(':LTESt:ACQuire:CTYPe:WAVeforms 32')
FlexDCA.write(':LTESt:ACQuire:STATe ON')
print('\nAcquiring 32 waveforms. Please wait...', flush=True)
FlexDCA.query(':ACQuire:RUN;*OPC?')
FlexDCA.write(':LTESt:ACQuire:STATe OFF')
def find_bit_sequence(FlexDCA, channel):
print('*' * 30)
print('A symbol sequence is a string of "1" and "0" characters.\n' +
'For example: 1110')
sequence = input('Enter a symbol sequence using symbols 0 and 1: ').strip()
if (sequence in 'qQ') or (sequence == ''):
return
sequence = sequence.strip('"')
sequence = sequence.strip("'")
FlexDCA.write(':TIMebase:UNITs UINTerval')
FlexDCA.write(':TIMebase:FIND:SIGNal CHAN' + channel)
FlexDCA.write(':TIMebase:FIND:SEQuence "' + sequence + '"')
i = float(FlexDCA.query(':TIMebase:UIPosition?'))
pattern_start = int(i)
total = 0
print('*' * 30)
while True:
FlexDCA.write(':TIMebase:FIND:NEXT')
i = float(FlexDCA.query(':TIMebase:UIPosition?'))
bit_offset = int(i)
bit = bit_offset - pattern_start
if bit == 0:
print('The bit sequence was not found.')
break
total += 1 # found sequence
if total == 1:
print('\nDisplayed span for "' + sequence + '" sequence is ' +
str(len(sequence)) + ' symbol.\n')
print('REPEATEDLY PRESS ENTER KEY until all sequences are found.')
print('Or, press "q" to exit.\n')
print('Symbol Sequences Found'.center(30, ' '))
print('-' * 30)
print(' Number Symbol Offset')
print('-' * 30)
first_found = bit
elif bit == first_found: # starting to repeat from beginning
print('\n' + str(total-1) + ' sequences have been found.')
break
s = str(total).rjust(3, ' ') + ' '
s += str(bit).ljust(5, ' ')
print(s.center(30, ' '), end='')
s = input()
if (s == 'q'):
break
FlexDCA = open_flexdca_connection(ADDRESS)
FlexDCA.query(':SYSTem:DEFault;*OPC?')
all_channels_off(FlexDCA)
install_simulated_module(FlexDCA, CHANNEL, 'DEM')
FlexDCA.write(':CHANnel' + CHANNEL + ':DISPlay ON')
setup(FlexDCA)
view_entire_pattern(FlexDCA)
waveform_acquisition(FlexDCA)
find_bit_sequence(FlexDCA, CHANNEL)
FlexDCA.write(':SYSTem:GTLocal')
FlexDCA.close()