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commented
9 years ago I wound up writing my own ctypes-based class for accessing the digital I/O
ports on
my NI-DAQ 6008. I based it on the examples given in
http://www.scipy.org/Cookbook/Data_Acquisition_with_NIDAQmx and the C code
provided
with the NIDAQmx 9.0.2 driver. As seen in the example python code at
scipy.org, it
uses nicaiu.dll to access the hardware. The code was tested and it seems to
work for
what I'm trying to do:
"""
This is an interpretation of the example program
C:\Documents and Settings\All Users\Documents\National
Instruments\NI-DAQ\Examples\DAQmx ANSI C\Digital\Generate Values\Write Dig
Chan\WriteDigChan.c
This routine allows you to access and set the digital output ports.
This module depends on:
numpy
Adapted by Martin Bures [ mbures { @ } zoll { . } com ]
Re-adapted by Matthew Last [ mlast { @ } trexenterprises { . } com]
"""
# import system libraries
import ctypes
import numpy as np
# load DLL
nidaq = ctypes.windll.nicaiu # load the DLL
##############################
# Setup some typedefs and constants
# to correspond with values in
# C:\Program Files\National Instruments\NI-DAQ\DAQmx ANSI C
Dev\include\NIDAQmx.h
# the typedefs
uint8 = ctypes.c_uint8
uInt32 = ctypes.c_ulong
uInt64 = ctypes.c_ulonglong
float64 = ctypes.c_double
TaskHandle = uInt32
# the constants
DAQmx_Val_ChanForAllLines = 1
DAQmx_Val_GroupByChannel = 0
class Ports( threading.Thread ):
"""
This class performs the necessary initialization of the DAQ hardware and
initializes the digital lines to low (digital 0)
"""
def __init__( self ):
self.port0 = [0,0,0,0,0,0,0,0]
self.port1 = [0,0,0,0]
self.taskHandle0 = TaskHandle( 0 )
self.taskHandle1 = TaskHandle( 0 )
# setup the DAQ hardware for port0 and port1
self.CHK(nidaq.DAQmxCreateTask("",
ctypes.byref( self.taskHandle0 )))
self.CHK(nidaq.DAQmxCreateTask("",
ctypes.byref( self.taskHandle1 )))
self.CHK(nidaq.DAQmxCreateDOChan( self.taskHandle0,
"Dev1/port0/line0:7",
"",
DAQmx_Val_ChanForAllLines))
self.CHK(nidaq.DAQmxCreateDOChan( self.taskHandle1,
"Dev1/port1/line0:3",
"",
DAQmx_Val_ChanForAllLines))
self.run(self.taskHandle0)
self.run(self.taskHandle1)
# Initialize digital ports
self.update( port0 = self.port0, port1 = self.port1)
def CHK( self, err ):
"""a simple error checking routine"""
if err < 0:
buf_size = 100
buf = ctypes.create_string_buffer('\000' * buf_size)
nidaq.DAQmxGetErrorString(err,ctypes.byref(buf),buf_size)
raise RuntimeError('nidaq call failed with error %d:
%s'%(err,repr(buf.value)))
if err > 0:
buf_size = 100
buf = ctypes.create_string_buffer('\000' * buf_size)
nidaq.DAQmxGetErrorString(err,ctypes.byref(buf),buf_size)
raise RuntimeError('nidaq generated warning %d: %s'%(err,repr(buf.value)))
def run( self, taskHandle ):
self.CHK(nidaq.DAQmxStartTask( taskHandle ))
def stop( self ):
nidaq.DAQmxStopTask( self.taskHandle0 )
nidaq.DAQmxClearTask( self.taskHandle0 )
def update(self, port0 = [0,0,0,0,0,0,0,0], port1 = [0,0,0,0]):
if len(port0) != 8:
raise ValueError('port0 argument must have 8 values')
if len(port1) != 4:
raise ValueError('port1 argument must have 4 values')
for i in range(len(port0)):
self.port0data[i] = port0[i]
for i in range(len(port1)):
self.port1data[i] = port1[i]
self.CHK(nidaq.DAQmxWriteDigitalLines( self.taskHandle0,
1, 1, float64(10.0),
DAQmx_Val_GroupByChannel,
self.port0data.ctypes.data,
None,
None))
self.CHK(nidaq.DAQmxWriteDigitalLines( self.taskHandle1,
1, 1, float64(10.0),
DAQmx_Val_GroupByChannel,
self.port1data.ctypes.data,
None,
None))Original comment by mattl...@gmail.com on 3 Dec 2009 at 1:04
Original issue reported on code.google.com by
mattl...@gmail.comon 2 Dec 2009 at 12:11