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Rev 1378 Rev 1550
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// Cosinus with argument in degree at an angular resolution of 1 degree and a discretisation of 13 bit.
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// Cosinus with argument in degree at an angular resolution of 1 degree and a discretisation of 13 bit.
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int16_t c_cos_8192(int16_t angle)
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int16_t c_cos_8192(int16_t angle)
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{
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{
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        return (c_sin_8192(90 - angle));
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        return (c_sin_8192(90 - angle));
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}
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}
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// Arcustangens returns degree in a range of +/. 180 deg
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const uint8_t pgm_atanlookup[346] PROGMEM = {0,1,2,3,4,4,5,6,7,8,9,10,11,11,12,13,14,15,16,17,17,18,19,20,21,21,22,23,24,24,25,26,27,27,28,29,29,30,31,31,32,33,33,34,35,35,36,36,37,37,38,39,39,40,40,41,41,42,42,43,43,44,44,45,45,45,46,46,47,47,48,48,48,49,49,50,50,50,51,51,51,52,52,52,53,53,53,54,54,54,55,55,55,55,56,56,56,57,57,57,57,58,58,58,58,59,59,59,59,60,60,60,60,60,61,61,61,61,62,62,62,62,62,63,63,63,63,63,63,64,64,64,64,64,64,65,65,65,65,65,65,66,66,66,66,66,66,66,67,67,67,67,67,67,67,68,68,68,68,68,68,68,68,69,69,69,69,69,69,69,69,69,70,70,70,70,70,70,70,70,70,71,71,71,71,71,71,71,71,71,71,71,72,72,72,72,72,72,72,72,72,72,72,73,73,73,73,73,73,73,73,73,73,73,73,73,73,74,74,74,74,74,74,74,74,74,74,74,74,74,74,75,75,75,75,75,75,75,75,75,75,75,75,75,75,75,75,75,76,76,76,76,76,76,76,76,76,76,76,76,76,76,76,76,76,76,76,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,77,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,78,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79,79};
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int16_t c_atan2(int16_t y, int16_t x)
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{
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        int16_t index, angle;
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        int8_t m;
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        if (!x && !y) return 0;         //atan2(0, 0) is undefined
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        if (y < 0) m = -1;
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        else m = 1;
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        if (!x) return (90 * m);                // atan2(y,0) = +/- 90 deg
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        index = (int16_t)(((int32_t)y * 64) / x);// calculate index for lookup table
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        if (index < 0) index = -index;
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        if (index < 346) angle = pgm_read_byte(&pgm_atanlookup[index]); // lookup for 0 deg to 79 deg
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        else if (index > 7334) angle = 90;                                              // limit is 90 deg
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        else if (index > 2444) angle = 89;                                              // 89 deg to 80 deg is mapped via intervalls
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        else if (index > 1465) angle = 88;
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        else if (index > 1046) angle = 87;
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        else if (index > 813) angle = 86;
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        else if (index > 664) angle = 85;
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        else if (index > 561) angle = 84;
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        else if (index > 486) angle = 83;
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        else if (index > 428) angle = 82;
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        else if (index > 382) angle = 81;
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        else angle = 80; // (index>345)
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        if (x > 0) return (angle * m);  // 1st and 4th quadrant
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        else if ((x < 0) && (m > 0)) return (180 - angle);      // 2nd quadrant
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        else return (angle - 180); // ( (x < 0) && (y < 0))     3rd quadrant
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}
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// Integer square root
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// For details of the algorithm see the article http://www.embedded.com/98/9802fe2.htm
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uint32_t c_sqrt(uint32_t a)
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{
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        uint32_t rem = 0;
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        uint32_t root = 0;
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        uint8_t i;
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        for(i = 0; i < 16; i++)
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        {
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                root <<= 1;
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                rem = ((rem << 2) + (a >> 30));
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                a <<= 2;
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                root++;
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                if(root <= rem)
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                {
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                        rem -= root;
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                        root++;
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                }
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                else root--;
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        }
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        return (root >> 1);
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}
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