Hello,
I'm dealing with an instrument that transfers numerical values through
an RS232 port in a custom (?) floating point representation (56 bits, 4
bits exponent and 52 bits significand).
Of course I need to convert this format to a standard IEEE 754 double to
be able to do anything useful with it. I came up with this simple code:
def tofloat(data):
# 56 bits floating point representation
# 4 bits exponent
# 52 bits significand
d = frombytes(data)
l = 56
p = l - 4
e = int(d >> p) + 17
v = 0
for i in xrange(p):
b = (d >> i) & 0x01
v += b * pow(2, i - p + e)
return v
where frombytes() is a simple function that assembles 7 bytes read from
the serial port into an integer for easing the manipulation:
def frombytes(bytes):
# convert from bytes string
value = 0
for i, b in enumerate(reversed(bytes)):
value += b * (1 << (i * 8))
return value
I believe that tofloat() can be simplified a bit, but except
optimizations (and cythonization) of this code, there is any simpler way
of achieving this?
Thanks. Cheers,
Daniele
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