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comparison logpps.py @ 62:ffc9292eb00b

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Use edge detection to log time differences between edges
author Daniel O'Connor <doconnor@gsoft.com.au>
date Fri, 08 Jan 2021 14:06:52 +1030
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children 7386f2888508
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61:b6dc43e6f6f0 62:ffc9292eb00b
1 #!/usr/bin/env python
2
3 # Copyright (c) 2021
4 # Daniel O'Connor <darius@dons.net.au>. All rights reserved.
5 #
6 # Redistribution and use in source and binary forms, with or without
7 # modification, are permitted provided that the following conditions
8 # are met:
9 # 1. Redistributions of source code must retain the above copyright
10 # notice, this list of conditions and the following disclaimer.
11 # 2. Redistributions in binary form must reproduce the above copyright
12 # notice, this list of conditions and the following disclaimer in the
13 # documentation and/or other materials provided with the distribution.
14 #
15 # THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 # ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
19 # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 # SUCH DAMAGE.
26 #
27 # Expected DB schema
28 # CREATE TABLE ppslog (
29 # name TEXT,
30 # time TIMESTAMP WITH TIME ZONE,
31 # delta NUMERIC(15, 12)
32 # );
33
34 import datetime
35 import matplotlib.pylab as pylab
36 import numpy
37 import psycopg2
38 #import sqlite3
39 import sys
40 import time
41 # Should try this code instead: https://github.com/python-ivi/python-usbtmc
42 import usb488
43
44 def main():
45 u = usb488.USB488Device()
46 print('Found device')
47
48 # See "TDS2000 Programmer.pdf"
49 res = u.ask('*IDN?')
50 print('IDN reports ' + res)
51
52 #dbh = sqlite3.connect('logpps.db')
53 dbh = psycopg2.connect('host=vm11 user=ppslog dbname=ppslog')
54 test(u, dbh, 'ncu-iono2-tx')
55
56 def test(u, dbh = None, name = None):
57 if dbh != None:
58 cur = dbh.cursor()
59
60 u.write('ACQ:MODE SAMPLE')
61 u.write('ACQ:STATE STOP')
62
63 #u.write('DATA:ENC RIB') # Big endian signed
64 #u.write('DATA:WIDTH 2') # 2 bytes wide
65
66 vscale1 = float(u.ask('CH1:SCALE?').split()[1])
67 print(('Channel 1 scale is %.2f volts/div' % (vscale1)))
68
69 vscale2 = float(u.ask('CH2:SCALE?').split()[1])
70 print(('Channel 2 scale is %.2f volts/div' % (vscale2)))
71
72 hscale = float(u.ask('HOR:MAIN:SCALE?').split()[1])
73 print(('Horizontal scale is %.5f nsec/div' % (hscale * 1e9)))
74 # TEK2024B doesn't grok HOR:DIV? so hard code 10 (has 8 vertically)
75 acqwindow = hscale * 10.0
76
77 while True:
78 ary1, ary2 = acquire(u, vscale1, vscale2)
79 #pylab.plot(ary1)
80 #pylab.plot(ary2)
81 #pylab.show()
82 sampletime = acqwindow / len(ary1)
83 d = getpdiffedge(ary1, ary2) * sampletime
84
85 print('Delta is %.1f nsec' % (d * 1e9))
86 if dbh != None:
87 now = datetime.datetime.now()
88 cur.execute('INSERT INTO ppslog(name, time, delta) VALUES(%s, %s, %s)', (name, now, d))
89 dbh.commit()
90
91 def getchannel(u, ch, vscale):
92 u.write('DAT:SOU CH%d' % (ch)) # Set the curve source to desired channel
93 result = u.ask('CURVE?', 1.0) # Ask for the curve data
94 data1 = result[13:] # Chop off the header (should verify this really..)
95 ary = numpy.frombuffer(data1, dtype = '>h')
96 ary = ary / 32768.0 * vscale # Scale to volts
97 return ary
98
99 def acquire(u, vscale1, vscale2):
100 u.write('ACQ:STATE 1') # Do a single acquisition
101 u.write('*OPC?')
102 u.read(2.0) # Wait for it to complete
103
104 ary1 = getchannel(u, 1, vscale1)
105 ary2 = getchannel(u, 2, vscale2)
106
107 return ary1, ary2
108
109 def getpdiffedge(ary1, ary2):
110 '''Return phase difference in samples between two signals by edge detection'''
111
112 # Rescale to 0-1
113 ary1 = ary1 - ary1.min()
114 ary1 = ary1 / ary1.max()
115 ary2 = ary2 - ary2.min()
116 ary2 = ary2 / ary2.max()
117
118 # Find rising edge of each
119 ary1pos = numpy.argmax(ary1 > 0.2)
120 ary2pos = numpy.argmax(ary2 > 0.2)
121
122 return ary1pos - ary2pos
123
124 if __name__ == '__main__':
125 main()