+++ /dev/null
-/*!
- * \file
- * <!--
- * Copyright 2004, 2008 Develer S.r.l. (http://www.develer.com/)
- * All Rights Reserved.
- * -->
- *
- * \brief Compute, save and load ramps for stepper motors (implementation)
- *
- * \version $Id$
- *
- * \author Simone Zinanni <s.zinanni@develer.com>
- * \author Bernardo Innocenti <bernie@develer.com>
- * \author Giovanni Bajo <rasky@develer.com>
- * \author Daniele Basile <asterix@develer.com>
- *
- *
- * The formula used by the ramp is the following:
- *
- * <pre>
- * a * b
- * f(t) = -------------
- * lerp(a,b,t)
- * </pre>
- *
- * Where <code>a</code> and <code>b</code> are the maximum and minimum speed
- * respectively (minimum and maximum wavelength respectively), and <code>lerp</code>
- * is a linear interpolation with a factor:
- *
- * <pre>
- * lerp(a,b,t) = a + t * (b - a) = (a * (1 - t)) + (b * t)
- * </pre>
- *
- * <code>t</code> must be in the [0,1] interval. It is easy to see that the
- * following holds true:
- *
- * <pre>
- * f(0) = b, f(1) = a
- * </pre>
- *
- * And that the function is monotonic. So, the function effectively interpolates
- * between the maximum and minimum speed through its domain ([0,1] -> [b,a]).
- *
- * The curve drawn by this function is similar to 1 / (sqrt(n)), so it is slower
- * than a linear acceleration (which would be 1/n).
- *
- * The floating point version uses a slightly modified function which accepts
- * the parameter in the domain [0, MT] (where MT is maxTime, the length of the
- * ramp, which is a setup parameter for the ramp). This is done to reduce the
- * number of operations per step. The formula looks like this:
- *
- * <pre>
- * a * b * MT
- * g(t) = ----------------------------
- * (a * MT) + t * (b - a)
- * </pre>
- *
- * It can be shown that this <code>g(t) = f(t * MT)</code>. The denominator
- * is a linear interpolation in the range [b*MT, a*MT], as t moves in the
- * interval [0, MT]. So the interpolation interval of the function is again
- * [b, a]. The implementation caches the value of the numerator and parts
- * of the denominator, so that the formula becomes:
- *
- * <pre>
- * alpha = a * b * MT
- * beta = a * MT
- * gamma = b - a
- *
- * alpha
- * g(t) = ----------------------
- * beta + t * gamma
- * </pre>
- *
- * and <code>t</code> is exactly the parameter that ramp_evaluate() gets,
- * that is the current time (in range [0, MT]). The operations performed
- * for each step are just an addition, a multiplication and a division.
- *
- * The fixed point version of the formula instead transforms the original
- * function as follows:
- *
- * <pre>
- * a * b a
- * f(t) = ------------------------- = --------------------
- * a a
- * b * ( - * (1 - t) + t ) - * (1 - t) + t
- * b b
- * </pre>
- *
- * <code>t</code> must be computed by dividing the current time (24 bit integer)
- * by the maximum time (24 bit integer). This is done by precomputing the
- * reciprocal of the maximum time as a 0.32 fixed point number, and multiplying
- * it to the current time. Multiplication is performed 8-bits a time by
- * FIX_MULT32(), so that we end up with a 0.16 fixed point number for
- * <code>t</code> (and <code>1-t</code> is just its twos-complement negation).
- * <code>a/b</code> is in the range [0,1] (because a is always less than b,
- * being the minimum wavelength), so it is precomputed as a 0.16 fixed point.
- * The final step is then computing the denominator and executing the division
- * (32 cycles using the 1-step division instruction in the DSP).
- *
- * The assembly implementation is needed for efficiency, but a C version of it
- * can be easily written, in case it is needed in the future.
- *
- */
-
-#include "ramp.h"
-#include <cfg/debug.h>
-
-#include <string.h> // memcpy()
-
-/**
- * Multiply \p a and \p b two integer at 32 bit and extract the high 16 bit word.
- */
-#define FIX_MULT32(a,b) (((uint64_t)(a)*(uint32_t)(b)) >> 16)
-
-void ramp_compute(struct Ramp *ramp, uint32_t clocksRamp, uint16_t clocksMinWL, uint16_t clocksMaxWL)
-{
- ASSERT(clocksMaxWL >= clocksMinWL);
-
- // Save values in ramp struct
- ramp->clocksRamp = clocksRamp;
- ramp->clocksMinWL = clocksMinWL;
- ramp->clocksMaxWL = clocksMaxWL;
-
-#if RAMP_USE_FLOATING_POINT
- ramp->precalc.gamma = ramp->clocksMaxWL - ramp->clocksMinWL;
- ramp->precalc.beta = (float)ramp->clocksMinWL * (float)ramp->clocksRamp;
- ramp->precalc.alpha = ramp->precalc.beta * (float)ramp->clocksMaxWL;
-
-#else
- ramp->precalc.max_div_min = ((uint32_t)clocksMinWL << 16) / (uint32_t)clocksMaxWL;
-
- /* Calcola 1/total_time in fixed point .32. Assumiamo che la rampa possa al
- * massimo avere 25 bit (cioé valore in tick fino a 2^25, che con il
- * prescaler=3 sono circa 7 secondi). Inoltre, togliamo qualche bit di precisione
- * da destra (secondo quanto specificato in RAMP_CLOCK_SHIFT_PRECISION).
- */
- ASSERT(ramp->clocksRamp < (1UL << (24 + RAMP_CLOCK_SHIFT_PRECISION)));
- ramp->precalc.inv_total_time = 0xFFFFFFFFUL / (ramp->clocksRamp >> RAMP_CLOCK_SHIFT_PRECISION);
- ASSERT(ramp->precalc.inv_total_time < 0x1000000UL);
-
-#endif
-}
-
-
-void ramp_setup(struct Ramp* ramp, uint32_t length, uint32_t minFreq, uint32_t maxFreq)
-{
- uint32_t minWL, maxWL;
-
- minWL = TIME2CLOCKS(FREQ2MICROS(maxFreq));
- maxWL = TIME2CLOCKS(FREQ2MICROS(minFreq));
-
- ASSERT2(minWL < 65536UL, "Maximum frequency too high");
- ASSERT2(maxWL < 65536UL, "Minimum frequency too high");
- ASSERT(maxFreq > minFreq);
-
- ramp_compute(
- ramp,
- TIME2CLOCKS(length),
- TIME2CLOCKS(FREQ2MICROS(maxFreq)),
- TIME2CLOCKS(FREQ2MICROS(minFreq))
- );
-}
-
-void ramp_default(struct Ramp *ramp)
-{
- ramp_setup(ramp, RAMP_DEF_TIME, RAMP_DEF_MINFREQ, RAMP_DEF_MAXFREQ);
-}
-
-#if RAMP_USE_FLOATING_POINT
-
-float ramp_evaluate(const struct Ramp* ramp, float curClock)
-{
- return ramp->precalc.alpha / (curClock * ramp->precalc.gamma + ramp->precalc.beta);
-}
-
-#else
-
-INLINE uint32_t fix_mult32(uint32_t m1, uint32_t m2)
-{
- uint32_t accum = 0;
- accum += m1 * ((m2 >> 0) & 0xFF);
- accum >>= 8;
- accum += m1 * ((m2 >> 8) & 0xFF);
- accum >>= 8;
- accum += m1 * ((m2 >> 16) & 0xFF);
- return accum;
-}
-
-// a*b >> 16
-INLINE uint16_t fix_mult16(uint16_t a, uint32_t b)
-{
- return (b*(uint32_t)a) >> 16;
-}
-
-uint16_t FAST_FUNC ramp_evaluate(const struct Ramp* ramp, uint32_t curClock)
-{
- uint16_t t = FIX_MULT32(curClock >> RAMP_CLOCK_SHIFT_PRECISION, ramp->precalc.inv_total_time);
- uint16_t denom = fix_mult16((uint16_t)~t + 1, ramp->precalc.max_div_min) + t;
- uint16_t cur_delta = ((uint32_t)ramp->clocksMinWL << 16) / denom;
-
- return cur_delta;
-}
-
-#endif
-
-
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