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neil.hamilton
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Add ps3000aExamples/ps3000aStreamingExample.py
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‎picosdk/ps3000a.py‎

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"""
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from ctypes import *
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from picosdk.ctypes_wrapper import C_CALLBACK_FUNCTION_FACTORY
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from picosdk.library import Library
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from picosdk.constants import make_enum
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‎ps3000aExamples/ps3000aStreamingExample.py‎

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#
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# Copyright (C) 2018-2020 Pico Technology Ltd. See LICENSE file for terms.
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#
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# PS3000 Series (A API) STREAMING MODE EXAMPLE
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# This example demonstrates how to call the ps3000a driver API functions in order to open a device, setup 2 channels and collects streamed data (1 buffer).
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# This data is then plotted as mV against time in ns.
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import ctypes
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import numpy as np
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from picosdk.ps3000a import ps3000a as ps
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import matplotlib.pyplot as plt
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from picosdk.functions import adc2mV, assert_pico_ok
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import time
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# Create chandle and status ready for use
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chandle = ctypes.c_int16()
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status = {}
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# Open PicoScope 5000 Series device
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status["openunit"] = ps.ps3000aOpenUnit(ctypes.byref(chandle), None)
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try:
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assert_pico_ok(status["openunit"])
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except: # PicoNotOkError:
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powerStatus = status["openunit"]
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if powerStatus == 286:
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status["changePowerSource"] = ps.ps3000aChangePowerSource(chandle, powerStatus)
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elif powerStatus == 282:
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status["changePowerSource"] = ps.ps3000aChangePowerSource(chandle, powerStatus)
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else:
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raise
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assert_pico_ok(status["changePowerSource"])
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enabled = 1
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disabled = 0
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analogue_offset = 0.0
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# Set up channel A
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# handle = chandle
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# channel = PS3000A_CHANNEL_A = 0
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# enabled = 1
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# coupling type = PS3000A_DC = 1
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# range = PS3000A_2V = 7
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# analogue offset = 0 V
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channel_range = ps.PS3000A_RANGE['PS3000A_2V']
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status["setChA"] = ps.ps3000aSetChannel(chandle,
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ps.PS3000A_CHANNEL['PS3000A_CHANNEL_A'],
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enabled,
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ps.PS3000A_COUPLING['PS3000A_DC'],
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channel_range,
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analogue_offset)
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assert_pico_ok(status["setChA"])
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# Set up channel B
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# handle = chandle
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# channel = PS3000A_CHANNEL_B = 1
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# enabled = 1
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# coupling type = PS3000A_DC = 1
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# range = PS3000A_2V = 7
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# analogue offset = 0 V
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status["setChB"] = ps.ps3000aSetChannel(chandle,
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ps.PS3000A_CHANNEL['PS3000A_CHANNEL_B'],
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enabled,
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ps.PS3000A_COUPLING['PS3000A_DC'],
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channel_range,
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analogue_offset)
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assert_pico_ok(status["setChB"])
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# Size of capture
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sizeOfOneBuffer = 500
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numBuffersToCapture = 10
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totalSamples = sizeOfOneBuffer * numBuffersToCapture
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# Create buffers ready for assigning pointers for data collection
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bufferAMax = np.zeros(shape=sizeOfOneBuffer, dtype=np.int16)
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bufferBMax = np.zeros(shape=sizeOfOneBuffer, dtype=np.int16)
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memory_segment = 0
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# Set data buffer location for data collection from channel A
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# handle = chandle
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# source = PS3000A_CHANNEL_A = 0
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# pointer to buffer max = ctypes.byref(bufferAMax)
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# pointer to buffer min = ctypes.byref(bufferAMin)
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# buffer length = maxSamples
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# segment index = 0
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# ratio mode = PS3000A_RATIO_MODE_NONE = 0
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status["setDataBuffersA"] = ps.ps3000aSetDataBuffers(chandle,
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ps.PS3000A_CHANNEL['PS3000A_CHANNEL_A'],
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bufferAMax.ctypes.data_as(ctypes.POINTER(ctypes.c_int16)),
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None,
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sizeOfOneBuffer,
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memory_segment,
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ps.PS3000A_RATIO_MODE['PS3000A_RATIO_MODE_NONE'])
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assert_pico_ok(status["setDataBuffersA"])
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# Set data buffer location for data collection from channel B
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# handle = chandle
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# source = PS3000A_CHANNEL_B = 1
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# pointer to buffer max = ctypes.byref(bufferBMax)
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# pointer to buffer min = ctypes.byref(bufferBMin)
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# buffer length = maxSamples
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# segment index = 0
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# ratio mode = PS3000A_RATIO_MODE_NONE = 0
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status["setDataBuffersB"] = ps.ps3000aSetDataBuffers(chandle,
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ps.PS3000A_CHANNEL['PS3000A_CHANNEL_B'],
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bufferBMax.ctypes.data_as(ctypes.POINTER(ctypes.c_int16)),
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None,
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sizeOfOneBuffer,
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memory_segment,
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ps.PS3000A_RATIO_MODE['PS3000A_RATIO_MODE_NONE'])
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assert_pico_ok(status["setDataBuffersB"])
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# Begin streaming mode:
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sampleInterval = ctypes.c_int32(250)
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sampleUnits = ps.PS3000A_TIME_UNITS['PS3000A_US']
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# We are not triggering:
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maxPreTriggerSamples = 0
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autoStopOn = 1
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# No downsampling:
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downsampleRatio = 1
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status["runStreaming"] = ps.ps3000aRunStreaming(chandle,
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ctypes.byref(sampleInterval),
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sampleUnits,
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maxPreTriggerSamples,
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totalSamples,
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autoStopOn,
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downsampleRatio,
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ps.PS3000A_RATIO_MODE['PS3000A_RATIO_MODE_NONE'],
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sizeOfOneBuffer)
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assert_pico_ok(status["runStreaming"])
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actualSampleInterval = sampleInterval.value
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actualSampleIntervalNs = actualSampleInterval * 1000
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print("Capturing at sample interval %s ns" % actualSampleIntervalNs)
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# We need a big buffer, not registered with the driver, to keep our complete capture in.
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bufferCompleteA = np.zeros(shape=totalSamples, dtype=np.int16)
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bufferCompleteB = np.zeros(shape=totalSamples, dtype=np.int16)
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nextSample = 0
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autoStopOuter = False
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wasCalledBack = False
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def streaming_callback(handle, noOfSamples, startIndex, overflow, triggerAt, triggered, autoStop, param):
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global nextSample, autoStopOuter, wasCalledBack
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wasCalledBack = True
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destEnd = nextSample + noOfSamples
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sourceEnd = startIndex + noOfSamples
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bufferCompleteA[nextSample:destEnd] = bufferAMax[startIndex:sourceEnd]
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bufferCompleteB[nextSample:destEnd] = bufferBMax[startIndex:sourceEnd]
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nextSample += noOfSamples
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if autoStop:
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autoStopOuter = True
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# Convert the python function into a C function pointer.
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cFuncPtr = ps.StreamingReadyType(streaming_callback)
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# Fetch data from the driver in a loop, copying it out of the registered buffers and into our complete one.
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while nextSample < totalSamples and not autoStopOuter:
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wasCalledBack = False
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status["getStreamingLastestValues"] = ps.ps3000aGetStreamingLatestValues(chandle, cFuncPtr, None)
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if not wasCalledBack:
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# If we weren't called back by the driver, this means no data is ready. Sleep for a short while before trying
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# again.
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time.sleep(0.01)
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print("Done grabbing values.")
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# Find maximum ADC count value
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# handle = chandle
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# pointer to value = ctypes.byref(maxADC)
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maxADC = ctypes.c_int16()
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status["maximumValue"] = ps.ps3000aMaximumValue(chandle, ctypes.byref(maxADC))
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assert_pico_ok(status["maximumValue"])
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# Convert ADC counts data to mV
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adc2mVChAMax = adc2mV(bufferCompleteA, channel_range, maxADC)
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adc2mVChBMax = adc2mV(bufferCompleteB, channel_range, maxADC)
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# Create time data
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time = np.linspace(0, (totalSamples) * actualSampleIntervalNs, totalSamples)
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# Plot data from channel A and B
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plt.plot(time, adc2mVChAMax[:])
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plt.plot(time, adc2mVChBMax[:])
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plt.xlabel('Time (ns)')
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plt.ylabel('Voltage (mV)')
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plt.show()
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# Stop the scope
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# handle = chandle
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status["stop"] = ps.ps3000aStop(chandle)
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assert_pico_ok(status["stop"])
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# Disconnect the scope
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# handle = chandle
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status["close"] = ps.ps3000aCloseUnit(chandle)
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assert_pico_ok(status["close"])
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# Display status returns
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print(status)

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