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by lordfrito
5 days ago
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> I think it is fair to argue that basic libraries don't support trig on common fixed point sizes. Its not that hard to roll your own support for fixed point trig. CORDIC is your friend. Easy to understand and easy to implement. Plus you can easily customize it for whatever custom fixed point size you want to work with. Back in the day I implemented fixed point SIN / COS / TAN / ATAN routines on an 8 bit micro. Angle was represented as 8.8 fixed point, with 256.0 = 360 degrees. Made it nice when adding and subtracting angle values, as 360 degrees would overflow back to zero degrees. SIN/COS values, being between 0.0 and 1.0, were stored as 0.16 bit fixed point, so FFFFh = 0.9998 (approx 1.0). Used it for embedded magnetometer and gyro applications. Worked great and was reasonably fast considering it was an 8 bit micro. |
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