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class BitaccessMeta(type):
"""meta class that adds bit access properties to a
parallel port implementation"""
def __new__(self, classname, bases, classdict):
klass = type.__new__(self, classname, bases, classdict)
#status lines
klass.paperOut = property(klass.getInPaperOut, None, "Read the PaperOut signal")
#control lines
klass.dataStrobe = property(None, klass.setDataStrobe, "Set the DataStrobe signal")
#XXX ... other bits
#data bits
for bit in range(8):
mask = (1<<bit)
def getter(self, mask=mask):
return (self.getData() & mask) != 0
def setter(self, b, mask=mask):
if b:
self.setData(self.getData() | mask)
else:
self.setData(self.getData() & ~mask)
setattr(klass, "D%d" % bit, property(getter, setter, "Access databit %d" % bit))
#nibbles
for name, shift, width in [('D0_D3', 0, 4), ('D4_D7', 4, 4)]:
mask = (1<<width) - 1
def getter(self, shift=shift, mask=mask):
return (self.getData() >> shift) & mask
def setter(self, b, shift=shift, mask=mask):
self.setData((self.getData() & ~(mask<<shift)) | ((b&mask) << shift))
setattr(klass, name, property(getter, setter, "Access to %s" % name))
return klass
class VirtualParallelPort:
"""provides a virtual parallel port implementation, useful
for tests and simulations without real hardware"""
__metaclass__ = BitaccessMeta
def __init__(self, port=None):
self._data = 0
def setData(self, value):
self._data = value
def getData(self):
return self._data
#inputs return dummy value
def getInPaperOut(self): return self._dummy
#...
#outputs just store a tuple with (action, value) pair
def setDataStrobe(self, value): self._last = ('setDataStrobe', value)
#...
#testing
if __name__ == '__main__':
import unittest, sys
class TestBitaccess(unittest.TestCase):
"""Tests a port with no timeout"""
def setUp(self):
self.p = VirtualParallelPort()
def testDatabits(self):
"""bit by bit D0..D7"""
p = self.p
p.D0 = p.D2 = p.D4 = p.D6 = 1
self.failUnlessEqual(p._data, 0x55)
self.failUnlessEqual(
[p.D7, p.D6, p.D5, p.D4, p.D3, p.D2, p.D1, p.D0],
[0, 1, 0, 1, 0, 1, 0, 1]
)
p._data <<= 1
self.failUnlessEqual(
[p.D7, p.D6, p.D5, p.D4, p.D3, p.D2, p.D1, p.D0],
[1, 0, 1, 0, 1, 0, 1, 0]
)
def testDatabitsGroups(self):
"""nibbles D0..D7"""
p = self.p
p.D0_D3 = 14
self.failUnlessEqual(p._data, 0x0e)
p.D0_D3 = 0
p.D4_D7 = 13
self.failUnlessEqual(p._data, 0xd0)
p.D0_D3 = p.D4_D7 = 0xa
self.failUnlessEqual(p._data, 0xaa)
#test bit patterns
for x in range(256):
#test getting
p._data = x
self.failUnlessEqual((p.D4_D7, p.D0_D3), (((x>>4) & 0xf), (x & 0xf)))
#test setting
p._data = 0
(p.D4_D7, p.D0_D3) = (((x>>4) & 0xf), (x & 0xf))
self.failUnlessEqual(p._data, x)
def testStatusbits(self):
"""bit by bit status lines"""
#read the property:
self.p._dummy = 0
self.failUnlessEqual(self.p.paperOut, 0)
self.p._dummy = 1
self.failUnlessEqual(self.p.paperOut, 1)
#read only, must not be writable:
self.failUnlessRaises(AttributeError, setattr, self.p, 'paperOut', 1)
def testControlbits(self):
"""bit by bit control lines"""
self.p.dataStrobe = 0
self.failUnlessEqual(self.p._last, ('setDataStrobe', 0))
self.p.dataStrobe = 1
self.failUnlessEqual(self.p._last, ('setDataStrobe', 1))
#write only, must not be writable:
self.failUnlessRaises(AttributeError, getattr, self.p, 'dataStrobe')
sys.argv.append('-v')
# When this module is executed from the command-line, it runs all its tests
unittest.main()
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