How do I convert a floating point C code to fixed point?
beagleboard, c, fixed-point, signal-processing, texas-instruments
Solution
TI provides a fixed-point library called "IQmath":
http://focus.ti.com/lit/sw/sprc990/sprc990.pdf
Converting involves analyzing your current code - for each variable you need to know what range it can hold, and what precision it needs. Then you can decide which type to store it in. IQMath provides types from q30 with a range of +/-2 and a precision of 0.0000000001 to q1 with a range of ~+/- 1 million and a precision of 0.5.
For operations which can possibly overflow the range of the variables, you need to add checks for overflow, and decide how to handle it - pin it at max, store with a different scale, raise an error, etc.
There is really no way to convert to fixed point without really gaining a deep understanding of the dataflow of your process.
Problem
I have a C code which uses doubles. I want to be able to run the code on a DSP (TMS320). But the DSP doesn't support doubles, only fixed-point numbers. What is the best way to convert the code into fixed-point? Is there a good C library for fixed-point numbers (implemented as integers)?