Revision 1586
Implementation of exponential. Not tested, don't even know if it works at all.
| trunk/code/projects/fp_math/fp_math.c | ||
|---|---|---|
| 10 | 10 |
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| 11 | 11 |
#define TABLE_LENGTH 64 |
| 12 | 12 |
#define TABLE_STEP 1621//.160757 |
| 13 |
#define EXP_MAGICONSTANT |
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| 13 | 14 |
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static inline int32_t trig_lookup(int32_t theta, int32_t* table); |
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static int32_t linspace[TABLE_LENGTH] PROGMEM = {
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| 17 | 16 |
0, 1621, 3242, 4863, 6485, 8106, 9727, 11348, |
| 18 | 17 |
12969, 14590, 16212, 17833, 19454, 21075, 22696, 24317, |
| ... | ... | |
| 44 | 43 |
return fp_cos(theta + FP_PI_OVER_TWO); |
| 45 | 44 |
} |
| 46 | 45 |
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int32_t fp_exp(int32_t x) {
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//Try with partial fractions for now. |
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int32_t xsquare = fp_mult(x,x); |
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int32_t result, i; |
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if(theta > EXP_MAGICONSTANT) {
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usb_puts("Output value is out of range.\n\r");
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return -1; |
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} |
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//This is again, massive amounts of lazyness. |
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//The approximation fails outside this range (approximately). |
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if(theta < -17) |
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return 0; |
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result = xsquare; |
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for(i= (22 << 16); i > (2 << 16); i-= (4 << 16)) {
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result += i; |
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result = fp_div(xsquare, result); |
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} |
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result += (2 << 16) - x; |
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return (1 << 16) + fp_div(fp_mult((2 << 16), x), result); |
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} |
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| 47 | 72 |
//Quadratic interpolation. |
| 48 | 73 |
int32_t fp_cos(int32_t theta) {
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| 49 | 74 |
uint8_t n; |
| ... | ... | |
| 69 | 94 |
n++; |
| 70 | 95 |
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| 71 | 96 |
//theta is between x_{n} and x_{n+1}
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| 73 | 97 |
if(n == TABLE_LENGTH - 1) {
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| 74 | 98 |
//Perform linear interpolation, since we're close to zero anyway. |
| 75 | 99 |
x_n = pgm_read_dword(&linspace[TABLE_LENGTH - 1]); |
| trunk/code/projects/fp_math/fp_math.h | ||
|---|---|---|
| 3 | 3 |
#define _FP_MATH_H_ |
| 4 | 4 |
|
| 5 | 5 |
#define FP_PI 205887 |
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#define FP_E 178145 |
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| 6 | 7 |
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| 7 | 8 |
#include <stdint.h> |
| 8 | 9 |
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