mozzi_utils.cpp

#include "mozzi_utils.h"

/** @ingroup util
Given a power of 2, work out the number to shift right by to do a divide by the number, or shift left to multiply.
@param a power of 2, or any other number for that matter
@return the number of trailing zeros on the right hand end
*/

/* NOTE: previous version is super-nifty, but pulls in software float code on AVR (the platform where it makes a difference), leading to bloat and a compile time warning.
 * Sine the only use-case I could find works on a compile-time constant (template-parameter), I added a constexpr function in mozzi_utils.h, instead. I renamed it, too,
 * so, we'll learn about any use-case outside of this scope. If there are no reports of breakage, the following can probably be removed for good.
long trailingZeros(unsigned long v) {
    // find the number of trailing zeros in v, from http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightFloatCast
    // there are faster methods on the bit twiddling site, but this is short
    float f = (float)(v & -v); // cast the least significant bit in v to a float
    return (*(uint32_t *)&f >> 23) - 0x7f;
}

Here's an alternate, trivial version:
uint8_t trailingZeros(uint16_t v) {
    uint8_t ret = 0;
    while ((v % 2) == 0) {
        v = v >> 1;
        ++ret;
    }
    return ret;
} */


    /** Convert BPM to milliseconds, which can be used to set the delay between beats for Metronome.
    @param bpm beats per minute
    */
    unsigned int BPMtoMillis(float bpm){
        float seconds_per_beat = 60.f/bpm;
        return (unsigned int) (seconds_per_beat*1000);
    }