I'm working on a little personal project (targeting a Parallax Propeller, but this should be pretty generalizable) that needs floating point math.
The micro-controller I am working with does not have native floating point, or a stock floating-point library.
Are there any good resources or tutorials on implementing software floating-point math? Preferably on really limited resources (I don't even have a stack!).
I'd like to support double sized floats. The propeller is a 32 bit MCU, so I'll have to use multiple variables for each float.
I know there is one software-floating-point library for the propeller out there, but it only supports single sized floats.
No, I probably don't really need double sized floats, but this sounds like a really interesting project. Half the reason I want to do this is because I'll learn a lot along the way.
Best Answer
If you want to do it yourself, I'd say just do it.
I guess you wont find too many resources or tutorial because there is not much to it.
Here is an outline:
adding/subtracting:
if exponents differ too much (more than the mantissa has bits):
just return the value with larger exponent (if this is the subtrahend: negate)
if exponents are similar:
shift the mantissa of smaller value by difference of exponents and add to/subtract from other mantissa (using fixed point arithmetic)
if result is not 0: shift mantissa up until MSBit of result is 1 and decrement exponent the same amount
multiplication/division:
multiply/divide mantissas (using fixed point arithmetic) and add/subtract exponents