Amund

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  1. I am using the python API for Waveforms to interface an Analog Discovery 2 and are trying monitor a voltage. The problem is that the measurements on channel 1 are capped to about 2.7 Volt wile channel 2 can measure up to 12.5 (the voltage I am supposed to measure) just fine. When I open Waveforms and use the scope there everything seems to work just fine. I am using the example code from AnalogIn_Record.py whit some small cleanup/modifications. Does anyone have an idea what I might be doing wrong? """ DWF Python Example Author: Digilent, Inc. Revision: 2018-07-19 Requires: Python 2.7, 3 """ from ctypes import * from dwfconstants import * import math import time import matplotlib.pyplot as plt import sys import numpy as np import signal dwf = cdll.LoadLibrary("/Library/Frameworks/dwf.framework/dwf") class AnalogDiscovery2(): def __init__(self): self.hdwf = c_int() dwf.FDwfDeviceOpen(c_int(-1), byref(hdwf)) def record_analog_in(self, pin, duartion): return def __del__(self): dwf.FDwfDeviceCloseAll() def rec(fs, duration_seconds=1, infinite=False): #declare ctype variables hdwf = c_int() sts = c_byte() hzAcq = c_double(fs) nSamples = duration_seconds * fs rgdSamples_1 = (c_double*nSamples)() rgdSamples_2 = (c_double*nSamples)() cAvailable = c_int() cLost = c_int() cCorrupted = c_int() fLost = 0 fCorrupted = 0 #open device print("Opening first device") dwf.FDwfDeviceOpen(c_int(-1), byref(hdwf)) if hdwf.value == hdwfNone.value: szerr = create_string_buffer(512) dwf.FDwfGetLastErrorMsg(szerr) print(str(szerr.value)) print("failed to open device") quit() #set up acquisition dwf.FDwfAnalogInChannelEnableSet(hdwf, c_int(0), c_bool(True)) dwf.FDwfAnalogInChannelRangeSet(hdwf, c_int(0), c_double(5)) dwf.FDwfAnalogInAcquisitionModeSet(hdwf, acqmodeRecord) dwf.FDwfAnalogInFrequencySet(hdwf, hzAcq) if infinite: dwf.FDwfAnalogInRecordLengthSet(hdwf, -1)#) # -1 infinite record length else: dwf.FDwfAnalogInRecordLengthSet(hdwf, c_double(nSamples/hzAcq.value)) #wait at least 2 seconds for the offset to stabilize time.sleep(2) print("Starting oscilloscope") dwf.FDwfAnalogInConfigure(hdwf, c_int(0), c_int(1)) cSamples = 0 time_start = time.time() while (cSamples < nSamples): dwf.FDwfAnalogInStatus(hdwf, c_int(1), byref(sts)) if cSamples == 0 and (sts == DwfStateConfig or sts == DwfStatePrefill or sts == DwfStateArmed) : # Acquisition not yet started. continue dwf.FDwfAnalogInStatusRecord(hdwf, byref(cAvailable), byref(cLost), byref(cCorrupted)) cSamples += cLost.value if cLost.value : fLost = 1 if cCorrupted.value : fCorrupted = 1 if cAvailable.value==0 : continue if cSamples+cAvailable.value > nSamples : cAvailable = c_int(nSamples-cSamples) dwf.FDwfAnalogInStatusData(hdwf, c_int(0), byref(rgdSamples_1, sizeof(c_double)*cSamples), cAvailable) # get channel 1 data dwf.FDwfAnalogInStatusData(hdwf, c_int(1), byref(rgdSamples_2, sizeof(c_double)*cSamples), cAvailable) # get channel 2 data cSamples += cAvailable.value time_used = time.time() - time_start dwf.FDwfAnalogOutReset(hdwf, c_int(0)) dwf.FDwfDeviceCloseAll() print("Recording done") if fLost: print("Samples were lost! Reduce frequency") if fCorrupted: print("Samples could be corrupted! Reduce frequency") data_1 = np.fromiter(rgdSamples_1, dtype = np.float) data_2 = np.fromiter(rgdSamples_2, dtype = np.float) t = np.linspace(0, time_used, len(data_1)) np.save("data_1", data_1) np.save("data_2", data_2) np.save("time", t) if __name__ == "__main__": rec(100, 2)