Python:DAQ 2

This page contains pictures and graphs related to DAQ 2 for EGR 103. It has been updated for Spring 2019 and Python.

Notes

• As before, if the system seems to not recognize Dev1, try Dev2 instead.

Pauses

There are intput commands in the code which will cause the program to wait for an input - specifically when the program first runs to check the lights. You will need to hit return to un-pause the program. The way to see if the program is paused is to look in the console to see if it is waiting for an input.

Resource Reserved / Task Cannot Start

If you get an error that a resources is reserved or that a task can't start, clear all the variables and re-run the script. Clearing the variables should clear all reservations to the DAQ card.

Typographical Errors

• An early edition had a typo on page 2-3 in the "Define useful functions" section; task should be taskout (fixed 0925, 13NOV).
• print_stats needs four inputs - change line 39 to:

def print_stats(vled, iled, popt, imod):

and change line 56 to:

        print_stats(vled, iled, popt, imod)

(fixed 0942, 13NOV)

Circuit for basic_aoutput

Circuit layout for BasicAOutput

Circuit for basic_aio

Circuit layout for BasicAIO

Graph from basic_aio

Graph showing output when

v_out = 2.5+2.5*npsin(2*np.pi*k/100);

That is,

\( \begin{align} V_{out}=2.5+2.5\sin\left(\frac{2\pi k}{100}\right) \end{align} \)

Circuit for aio

Circuit layout for aio

Graph from aio

Graph showing outputs from three measurement channels. Note at the far left that they all start at either exactly 0 V!

Codes

Here are the codes references in the assignment.

basic_aoutput.py

 1 #%% Import modules
 2 import numpy as np
 3 import time
 4 import PyDAQmx as daq
 5 
 6 
 7 
 8 #%% Create a task
 9 taskout = daq.Task()
10 
11 
12 #%% Set Channel Counts
13 a_out  = 1
14 
15 
16 #%% Add analog output lines
17 taskout.CreateAOVoltageChan('Dev1/ao0:{}'.format(a_out-1),'', 
18                          -10.0,10.0,daq.DAQmx_Val_Volts,None)
19 
20 
21 
22 
23 
24 
25 #%% Define useful functions
26 # Function to change daq outputs
27 def write_volts(data):
28     taskout.WriteAnalogScalarF64(1,10.0,data,None)
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 #%% Stop and start tasks
40 taskout.StopTask()
41 taskout.StartTask()
42 
43 
44 
45 #%% Check lights
46 write_volts(5)
47 input('PAUSED - Hit return to continue ')
48 print('Running')
49 write_volts(0)
50 
51 #%% Write values to output
52 
53 for k in range(300):
54     v_out = 2.5+2.5*np.sin(2*np.pi*k/100)
55     write_volts(v_out)
56     time.sleep(0.01)
57 
58 
59 #%% Turn all off when finished and stop task
60 write_volts(0)
61 taskout.StopTask()

basic_aio.py

 1 #%% Import modules
 2 import numpy as np
 3 import time
 4 import PyDAQmx as daq
 5 import ctypes
 6 import matplotlib.pyplot as plt
 7 
 8 #%% Create a task
 9 taskout = daq.Task()
10 taskin  = daq.Task()
11 
12 #%% Set Channel Counts
13 a_out = 1
14 a_in  = 1
15  
16 #%% Add analog output lines
17 taskout.CreateAOVoltageChan('Dev1/ao0:{}'.format(a_out-1),'', 
18                          -10.0,10.0,daq.DAQmx_Val_Volts,None)
19 
20 #%% Add analog input lines
21 taskin.CreateAIVoltageChan('Dev1/ai0:{}'.format(a_in-1),'', 
22                            daq.DAQmx_Val_Cfg_Default,
23                          -10.0,10.0,daq.DAQmx_Val_Volts,None)
24 
25 #%% Define useful functions
26 # Function to change daq outputs
27 def write_volts(data):
28     taskout.WriteAnalogScalarF64(1,10.0,data,None)
29     
30 # Function to read daq outputs
31 def read_volts():
32     data = np.zeros((1,a_in), dtype=np.float64)
33     read = ctypes.c_int32()
34     taskin.ReadAnalogF64(1,10.0,
35                          daq.DAQmx_Val_GroupByChannel,
36                          data, a_in, ctypes.byref(read), None)
37     return data
38 
39 #%% Stop and start tasks
40 taskout.StopTask()
41 taskin.StopTask()
42 taskout.StartTask()
43 taskin.StartTask()
44 
45 #%% Check lights
46 write_volts(5)
47 input('PAUSED - Hit return to continue ')
48 print('Running')
49 write_volts(0)
50 
51 #%% Write and read values
52 meas = np.zeros((300,3), dtype=np.float64)
53 for k in range(300):
54     v_out = 2.5+2.5*np.sin(2*np.pi*k/100)
55     write_volts(v_out)
56     time.sleep(0.01)
57     meas[k,:] = read_volts()
58 
59 #%% Turn all off when finished and stop task
60 write_volts(0)
61 taskout.StopTask()
62 taskin.StopTask()
63 
64 #%% Make plots
65 plt.figure(1)
66 plt.clf()
67 total = meas[:,0]
68 
69 
70 plt.plot(total, 'b')

aio script

 1 #%% Import modules
 2 import numpy as np
 3 import time
 4 import PyDAQmx as daq
 5 import ctypes
 6 import matplotlib.pyplot as plt
 7 
 8 #%% Create a task
 9 taskout = daq.Task()
10 taskin  = daq.Task()
11 
12 #%% Set Channel Counts
13 a_in  = 3
14 a_out = 1
15  
16 #%% Add analog output lines
17 taskout.CreateAOVoltageChan('Dev1/ao0:{}'.format(a_out-1),'', 
18                          -10.0,10.0,daq.DAQmx_Val_Volts,None)
19 
20 #%% Add analog input lines
21 taskin.CreateAIVoltageChan('Dev1/ai0:{}'.format(a_in-1),'', 
22                            daq.DAQmx_Val_Cfg_Default,
23                          -10.0,10.0,daq.DAQmx_Val_Volts,None)
24 
25 #%% Define useful functions
26 # Function to change daq outputs
27 def write_volts(data):
28     taskout.WriteAnalogScalarF64(1,10.0,data,None)
29     
30 # Function to read daq outputs
31 def read_volts():
32     data = np.zeros((1,a_in), dtype=np.float64)
33     read = ctypes.c_int32()
34     taskin.ReadAnalogF64(1,10.0,
35                          daq.DAQmx_Val_GroupByChannel,
36                          data, a_in, ctypes.byref(read), None)
37     return data
38 
39 #%% Stop and start task
40 taskout.StopTask()
41 taskin.StopTask()
42 taskout.StartTask()
43 taskin.StartTask()
44 
45 #%% Check lights
46 write_volts(5)
47 input('PAUSED - Hit return to continue ')
48 print('Running')
49 write_volts(0)
50 
51 #%% Write and read values
52 meas = np.zeros((300,3), dtype=np.float64)
53 for k in range(300):
54     v_out = (k/299)*10
55     write_volts(v_out)
56     time.sleep(0.01)
57     meas[k,:] = read_volts()
58 
59 #%% Turn all off when finished and stop task
60 write_volts(0)
61 taskout.StopTask()
62 taskin.StopTask()
63 
64 #%% Make plots
65 plt.figure(1)
66 plt.clf()
67 total = meas[:,0]
68 resv = meas[:,1]
69 ledv = meas[:,2]
70 plt.plot(total, 'b', resv, 'g', ledv, 'r')
71 plt.legend(['$v_s$', '$v_R$', '$v_{LED}$'])
72 
73 #%% Save values and figure
74 color = input('Color: ')
75 eval("plt.title('{:s}')".format(color))
76 fid=eval("open('{:s}_data.dat', 'w')".format(color))
77 for k in range(300):
78     fid.write('{:.4e} {:.4e} {:.4e}\n'.format(*meas[k,:]))
79 fid.close()
80 eval("plt.savefig('{:s}_plot.png')".format(color))

Questions

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