#!/usr/bin/env python

# Copyright (c) 2009
#      Daniel O'Connor <darius@dons.net.au>.  All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#

import matplotlib.pylab as pylab
import numpy
import scpi
import time
import usb488

def test(u):
    u.write("*IDN?")
    print "IDN reports " + u.read()
    
    # Set data format to 16 bit big endian signed
    u.write("DATA:ENC RIB")
    u.write("DATA:WIDTH 2")

    # Turn channel 1 on
    u.write("SELECT:CH1 ON")

    # Set the curve source to channel 1
    u.write("DATA:SOURCE CH1")

    # Fetch channel scale
    u.write("CH1:SCALE?")
    vscale = float(u.read(1).split()[1])
    print "Channel 1 scale is %.2f volts/div" % (vscale)

    # Fetch horizontal scale
    u.write("HOR:MAIN:SCALE?")
    hscale = float(u.read(1).split()[1])
    print "Horizontal scale is %f sec/div" % (hscale)

    # Make sure the previous commands have been executed
    u.write("*WAI")

    # Fetch curve data (wait up to 1 second)
    u.write("CURVE?")
    then = time.time()                            
    result = u.read(1.0)
    now = time.time()
    print "CURVE read took %f milliseconds" % ((now - then) * 1000.0)

    # Parse data
    ary = scpi.bindecode(result, header = ':CURVE ', dtype = numpy.dtype('>h'))

    # Convert to volts
    ary = ary / 32768.0 * vscale

    # Plot data
    pylab.plot(ary)
    pylab.show()
    
if __name__ == "__main__":
    u = usb488.USB488Device()
    print "Found device"

    test(u)