annotate phasediff.py @ 61:b6dc43e6f6f0

Add code to measure phase difference between 2 signals by sampling from the cro.
author Daniel O'Connor <doconnor@gsoft.com.au>
date Fri, 08 Jan 2021 14:06:27 +1030
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1 #!/usr/bin/env python
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2
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3
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4
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5 # Copyright (c) 2020
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6 # Daniel O'Connor <darius@dons.net.au>. All rights reserved.
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7 #
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8 # Redistribution and use in source and binary forms, with or without
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9 # modification, are permitted provided that the following conditions
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10 # are met:
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11 # 1. Redistributions of source code must retain the above copyright
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12 # notice, this list of conditions and the following disclaimer.
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13 # 2. Redistributions in binary form must reproduce the above copyright
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14 # notice, this list of conditions and the following disclaimer in the
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15 # documentation and/or other materials provided with the distribution.
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16 #
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17 # THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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18 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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19 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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20 # ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
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21 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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22 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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23 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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24 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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25 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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26 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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27 # SUCH DAMAGE.
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28 #
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29
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30 # Expected DB schema
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31 # CREATE TABLE phasediff (
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32 # name TEXT,
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33 # time TIMESTAMP WITH TIME ZONE,
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34 # delta NUMERIC(15, 12),
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35 # cumulative NUMERIC(15, 12)
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36 # );
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37
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38 import datetime
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39 import matplotlib.pylab as pylab
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40 import numpy
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41 import psycopg2
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42 import scipy.signal
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43 import sqlite3
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44 import sys
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45 import time
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46 # Should try this code instead: https://github.com/python-ivi/python-usbtmc
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47 import usb488
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48
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49 def main():
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50 u = usb488.USB488Device()
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51 print('Found device')
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52
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53 # See "TDS2000 Programmer.pdf"
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54 u.write('*IDN?')
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55 print(('IDN reports ' + u.read()))
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56
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57 #dbh = sqlite3.connect('phasediff.db')
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58 dbh = psycopg2.connect('host=vm11 user=phasediff dbname=phasediff')
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59 test(u, dbh, 'delamerelts')
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60
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61 def test(u, dbh = None, name = None):
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62 if dbh != None:
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63 cur = dbh.cursor()
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64
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65 u.write('DATA:ENC RIB') # Big endian signed
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66 u.write('DATA:WIDTH 2') # 2 bytes wide
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67
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68 u.write('CH1:SCALE?')
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69 vscale1 = float(u.read(1).split()[1])
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70 print(('Channel 1 scale is %.2f volts/div' % (vscale1)))
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71 u.write('CH2:SCALE?')
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72 vscale2 = float(u.read(1).split()[1])
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73 print(('Channel 2 scale is %.2f volts/div' % (vscale2)))
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74 u.write('HOR:MAIN:SCALE?')
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75 hscale = float(u.read(1).split()[1])
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76 print(('Horizontal scale is %.5f nsec/div' % (hscale * 1e9)))
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77 # TEK2024B doesn't grok HOR:DIV? so hard code 10 (has 8 vertically)
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78 acqwindow = hscale * 10.0
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79 nomclockperiod = 1 / 10.7e6
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80
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81 cumdiff = 0
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82 lastdiff = None
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83 while True:
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84 ary1, ary2 = acquire(u, vscale1, vscale2)
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85
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86 sampletime = acqwindow / len(ary1)
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87
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88 # Compute clock periods
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89 # XXX: this is pretty noisy so we use the nominal clock period above for unwrapping
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90 #period1 = getperiod(ary1) * sampletime
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91 #period2 = getperiod(ary2) * sampletime
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92
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93 # Compute phased difference between the two
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94 d = getpdiff(ary1, ary2) * sampletime
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95 #d = getpdiffedge(ary1, ary2) * sampletime
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96 if lastdiff == None:
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97 # First time, init variables and start again
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98 # XXX: should get the most recent cumuulative diff from the DB really..
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99 lastdiff = d
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100 cumdiff = d
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101 continue
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102
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103 # Difference between difference
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104 diff = d - lastdiff
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105
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106 # Check if it wrapped
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107 if abs(diff) > nomclockperiod / 2:
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108 if d > nomclockperiod / 2:
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109 diff -= nomclockperiod
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110 else:
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111 diff += nomclockperiod
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112
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113 # Accumulate deltas
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114 cumdiff += diff
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115
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116 # Log / insert into DB
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117 now = datetime.datetime.now()
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118 print(("%s Cumulative: %.2f nsec Delta: %.2f nsec Diff: %.2f nsec" % (
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119 now.strftime('%Y/%m/%d %H:%M:%S.%f'),
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120 cumdiff * 1e9, d * 1e9, diff * 1e9)))
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121 if dbh != None:
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122 cur.execute('INSERT INTO phasediff(name, time, delta, cumulative) VALUES(%s, %s, %s, %s)', (name, now, d, cumdiff))
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123 dbh.commit()
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124 lastdiff = d
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125
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126 def acquire(u, vscale1, vscale2):
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127 u.write('ACQ:STATE 1') # Do a single acquisition
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128 u.write('*OPC?')
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129 u.read(2.0) # Wait for it to complete
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130
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131 u.write('DAT:SOU CH1') # Set the curve source to channel 1
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132 u.write('CURVE?') # Ask for the curve data
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133 then = time.time()
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134 result = u.read(1.0) # Takes the CRO a while for this
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135 now = time.time()
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136 #print('CURVE read took %f milliseconds' % ((now - then) * 1000.0))
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137 data1 = result[13:] # Chop off the header (should verify this really..)
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138 ary1 = numpy.fromstring(data1, dtype = '>h')
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139 ary1 = ary1 / 32768.0 * vscale1 # Scale to volts
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140
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141 u.write('DAT:SOU CH2') # Set the curve source to channel 2
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142 u.write('CURVE?') # Ask for the curve data
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143 then = time.time()
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144 result = u.read(1.0) # Takes the CRO a while for this
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145 now = time.time()
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146 #print('CURVE read took %f milliseconds' % ((now - then) * 1000.0))
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147 data2 = result[13:] # Chop off the header (should verify this really..)
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148 ary2 = numpy.fromstring(data2, dtype = '>h')
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149 ary2 = ary2 / 32768.0 * vscale2 # Scale to volts
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150
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151 return ary1, ary2
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152
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153 def getpdiff(ary1, ary2):
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154 '''Return phase difference in samples between two signals by cross correlation'''
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155
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156 # Rescale to 0-1
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157 ary1 = ary1 - ary1.min()
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158 ary1 = ary1 / ary1.max()
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159 ary2 = ary2 - ary2.min()
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160 ary2 = ary2 / ary2.max()
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161
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162 # Cross correlate
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163 corr = scipy.signal.correlate(ary1, ary2)
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164
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165 # Find peak
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166 amax = corr.argmax()
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167
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168 return amax - (len(ary1) - 1)
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169
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170 def getpdiffedge(ary1, ary2):
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171 '''Return phase difference in samples between two signals by edge detection'''
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172
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173 # Rescale to 0-1
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174 ary1 = ary1 - ary1.min()
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175 ary1 = ary1 / ary1.max()
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176 ary2 = ary2 - ary2.min()
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177 ary2 = ary2 / ary2.max()
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178
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179 # Find rising edge of each
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180 ary1pos = numpy.argmax(ary1 > 0.2)
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181 ary2pos = numpy.argmax(ary2 > 0.2)
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182
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183 return ary1pos - ary2pos
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184
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185 def getperiod(ary):
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186 '''Return period of signal in ary in samples'''
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187 # Compute auto correlation
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188 corr = scipy.signal.correlate(ary, ary)
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189
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190 # Find peaks
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191 peaks, _ = scipy.signal.find_peaks(corr)
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192
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193 # Find time differences between peaks
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194 deltapeak = (peaks[1:-1] - peaks[0:-2])
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195
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196 # Return average of the middle few
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197 return deltapeak[2:-2].mean()
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198
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199 def trend(dbh, name):
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200 cur = dbh.cursor()
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201 cur2 = dbh.cursor()
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202 cur.execute('SELECT time, deltansec FROM phasediff WHERE name = %s', (name, ))
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203
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204 _, lastdelta = cur.fetchone()
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205
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206 count = 0
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207 cumdiff = 0
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208 for row in cur:
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209 time, delta = row
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210 diff = float(delta - lastdelta)
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211 if abs(diff) > 45e-9:
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212 if delta > 45e-9:
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213 diff -= 1.0 / 10.7e6
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214 else:
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215 diff += 1.0 / 10.7e6
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216 cumdiff += diff
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217 #print('Cumulative: %.5f nsec Delta: %.5f nsec Last: %.5f nsec Diff: %.5f nsec' % (
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218 # float(cumdiff) * 1e9, float(delta) * 1e9, float(lastdelta) * 1e9, float(diff) * 1e9))
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219 lastdelta = delta
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220 cur2.execute('INSERT INTO cumdiff (name, time, cummdiff) VALUES (%s, %s, %s)',
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221 ( name, time, cumdiff))
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222 count += 1
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223 #if count % 20 == 0:
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224 # sys.stdin.readline()
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225 if count % 1000 == 0:
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226 dbh.commit()
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227 print(('Count %d: %s' % (count, str(time))))
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228
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229 if __name__ == '__main__':
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230 main()