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lib8tion.h
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lib8tion.h
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#ifndef __INC_LIB8TION_H
#define __INC_LIB8TION_H
/*
Fast, efficient 8-bit math functions specifically
designed for high-performance LED programming.
Because of the AVR(Arduino) and ARM assembly language
implementations provided, using these functions often
results in smaller and faster code than the equivalent
program using plain "C" arithmetic and logic.
Included are:
- Saturating unsigned 8-bit add and subtract.
Instead of wrapping around if an overflow occurs,
these routines just 'clamp' the output at a maxumum
of 255, or a minimum of 0. Useful for adding pixel
values. E.g., qadd8( 200, 100) = 255.
qadd8( i, j) == MIN( (i + j), 0xFF )
qsub8( i, j) == MAX( (i - j), 0 )
- Saturating signed 8-bit ("7-bit") add.
qadd7( i, j) == MIN( (i + j), 0x7F)
- Scaling (down) of unsigned 8- and 16- bit values.
Scaledown value is specified in 1/256ths.
scale8( i, sc) == (i * sc) / 256
scale16by8( i, sc) == (i * sc) / 256
Example: scaling a 0-255 value down into a
range from 0-99:
downscaled = scale8( originalnumber, 100);
A special version of scale8 is provided for scaling
LED brightness values, to make sure that they don't
accidentally scale down to total black at low
dimming levels, since that would look wrong:
scale8_video( i, sc) = ((i * sc) / 256) +? 1
Example: reducing an LED brightness by a
dimming factor:
new_bright = scale8_video( orig_bright, dimming);
- Fast 8- and 16- bit unsigned random numbers.
Significantly faster than Arduino random(), but
also somewhat less random. You can add entropy.
random8() == random from 0..255
random8( n) == random from 0..(N-1)
random8( n, m) == random from N..(M-1)
random16() == random from 0..65535
random16( n) == random from 0..(N-1)
random16( n, m) == random from N..(M-1)
random16_set_seed( k) == seed = k
random16_add_entropy( k) == seed += k
- Absolute value of a signed 8-bit value.
abs8( i) == abs( i)
- 8-bit math operations which return 8-bit values.
These are provided mostly for completeness,
not particularly for performance.
mul8( i, j) == (i * j) & 0xFF
add8( i, j) == (i + j) & 0xFF
sub8( i, j) == (i - j) & 0xFF
- Fast 16-bit approximations of sin and cos.
Input angle is a uint16_t from 0-65535.
Output is a signed int16_t from -32767 to 32767.
sin16( x) == sin( (x/32768.0) * pi) * 32767
cos16( x) == cos( (x/32768.0) * pi) * 32767
Accurate to more than 99% in all cases.
- Dimming and brightening functions for 8-bit
light values.
dim8_video( x) == scale8_video( x, x)
dim8_raw( x) == scale8( x, x)
brighten8_video( x) == 255 - dim8_video( 255 - x)
brighten8_raw( x) == 255 - dim8_raw( 255 - x)
The dimming functions in particular are suitable
for making LED light output appear more 'linear'.
- Fast 8-bit "easing in/out" function.
ease8InOutCubic(x) == 3(x^i) - 2(x^3)
ease8InOutApprox(x) ==
faster, rougher, approximation of cubic easing
- Linear interpolation between two values, with the
fraction between them expressed as an 8- or 16-bit
fixed point fraction (fract8 or fract16).
lerp8by8( fromU8, toU8, fract8 )
lerp16by8( fromU16, toU16, fract8 )
lerp15by8( fromS16, toS16, fract8 )
== from + (( to - from ) * fract8) / 256)
lerp16by16( fromU16, toU16, fract16 )
== from + (( to - from ) * fract16) / 65536)
- Optimized memmove, memcpy, and memset, that are
faster than standard avr-libc 1.8.
memmove8( dest, src, bytecount)
memcpy8( dest, src, bytecount)
memset8( buf, value, bytecount)
Lib8tion is pronounced like 'libation': lie-BAY-shun
*/
#include <stdint.h>
#define LIB8STATIC __attribute__ ((unused)) static
#if defined(__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__) || defined(__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
#define LIB8_ATTINY 1
#endif
#if defined(__arm__)
#if defined(__MK20DX128__)
// Can use Cortex M4 DSP instructions
#define QADD8_C 0
#define QADD7_C 0
#define QADD8_ARM_DSP_ASM 1
#define QADD7_ARM_DSP_ASM 1
#else
// Generic ARM
#define QADD8_C 1
#define QADD7_C 1
#endif
#define QSUB8_C 1
#define SCALE8_C 1
#define SCALE16BY8_C 1
#define SCALE16_C 1
#define ABS8_C 1
#define MUL8_C 1
#define QMUL8_C 1
#define ADD8_C 1
#define SUB8_C 1
#define EASE8_C 1
#elif defined(__AVR__)
// AVR ATmega and friends Arduino
#define QADD8_C 0
#define QADD7_C 0
#define QSUB8_C 0
#define ABS8_C 0
#define ADD8_C 0
#define SUB8_C 0
#define QADD8_AVRASM 1
#define QADD7_AVRASM 1
#define QSUB8_AVRASM 1
#define ABS8_AVRASM 1
#define ADD8_AVRASM 1
#define SUB8_AVRASM 1
// Note: these require hardware MUL instruction
// -- sorry, ATtiny!
#if !defined(LIB8_ATTINY)
#define SCALE8_C 0
#define SCALE16BY8_C 0
#define SCALE16_C 0
#define MUL8_C 0
#define QMUL8_C 0
#define EASE8_C 0
#define SCALE8_AVRASM 1
#define SCALE16BY8_AVRASM 1
#define SCALE16_AVRASM 1
#define MUL8_AVRASM 1
#define QMUL8_AVRASM 1
#define EASE8_AVRASM 1
#define CLEANUP_R1_AVRASM 1
#else
// On ATtiny, we just use C implementations
#define SCALE8_C 1
#define SCALE16BY8_C 1
#define SCALE16_C 1
#define MUL8_C 1
#define QMUL8_C 1
#define EASE8_C 1
#define SCALE8_AVRASM 0
#define SCALE16BY8_AVRASM 0
#define SCALE16_AVRASM 0
#define MUL8_AVRASM 0
#define QMUL8_AVRASM 0
#define EASE8_AVRASM 0
#endif
#else
// unspecified architecture, so
// no ASM, everything in C
#define QADD8_C 1
#define QADD7_C 1
#define QSUB8_C 1
#define SCALE8_C 1
#define SCALE16BY8_C 1
#define SCALE16_C 1
#define ABS8_C 1
#define MUL8_C 1
#define ADD8_C 1
#define SUB8_C 1
#define EASE8_C 1
#endif
///////////////////////////////////////////////////////////////////////
//
// typdefs for fixed-point fractional types.
//
// sfract7 should be interpreted as signed 128ths.
// fract8 should be interpreted as unsigned 256ths.
// sfract15 should be interpreted as signed 32768ths.
// fract16 should be interpreted as unsigned 65536ths.
//
// Example: if a fract8 has the value "64", that should be interpreted
// as 64/256ths, or one-quarter.
//
//
// fract8 range is 0 to 0.99609375
// in steps of 0.00390625
//
// sfract7 range is -0.9921875 to 0.9921875
// in steps of 0.0078125
//
// fract16 range is 0 to 0.99998474121
// in steps of 0.00001525878
//
// sfract15 range is -0.99996948242 to 0.99996948242
// in steps of 0.00003051757
//
typedef uint8_t fract8; // ANSI: unsigned short _Fract
typedef int8_t sfract7; // ANSI: signed short _Fract
typedef uint16_t fract16; // ANSI: unsigned _Fract
typedef int16_t sfract15; // ANSI: signed _Fract
// accumXY types should be interpreted as X bits of integer,
// and Y bits of fraction.
// E.g., accum88 has 8 bits of int, 8 bits of fraction
typedef uint16_t accum88; // ANSI: unsigned short _Accum
typedef int16_t saccum78; // ANSI: signed short _Accum
typedef uint32_t accum1616;// ANSI: signed _Accum
typedef int32_t saccum1516;//ANSI: signed _Accum
typedef uint16_t accum124; // no direct ANSI counterpart
typedef int32_t saccum114;// no direct ANSI counterpart
// typedef for IEEE754 "binary32" float type internals
typedef union {
uint32_t i;
float f;
struct {
uint32_t mantissa: 23;
uint32_t exponent: 8;
uint32_t signbit: 1;
};
struct {
uint32_t mant7 : 7;
uint32_t mant16: 16;
uint32_t exp_ : 8;
uint32_t sb_ : 1;
};
struct {
uint32_t mant_lo8 : 8;
uint32_t mant_hi16_exp_lo1 : 16;
uint32_t sb_exphi7 : 8;
};
} IEEE754binary32_t;
///////////////////////////////////////////////////////////////////////
// qadd8: add one byte to another, saturating at 0xFF
LIB8STATIC uint8_t qadd8( uint8_t i, uint8_t j)
{
#if QADD8_C == 1
int t = i + j;
if( t > 255) t = 255;
return t;
#elif QADD8_AVRASM == 1
asm volatile(
/* First, add j to i, conditioning the C flag */
"add %0, %1 \n\t"
/* Now test the C flag.
If C is clear, we branch around a load of 0xFF into i.
If C is set, we go ahead and load 0xFF into i.
*/
"brcc L_%= \n\t"
"ldi %0, 0xFF \n\t"
"L_%=: "
: "+a" (i)
: "a" (j) );
return i;
#elif QADD8_ARM_DSP_ASM == 1
asm volatile( "uqadd8 %0, %0, %1" : "+r" (i) : "r" (j));
return i;
#else
#error "No implementation for qadd8 available."
#endif
}
// qadd7: add one signed byte to another,
// saturating at 0x7F.
LIB8STATIC int8_t qadd7( int8_t i, int8_t j)
{
#if QADD7_C == 1
int16_t t = i + j;
if( t > 127) t = 127;
return t;
#elif QADD7_AVRASM == 1
asm volatile(
/* First, add j to i, conditioning the V flag */
"add %0, %1 \n\t"
/* Now test the V flag.
If V is clear, we branch around a load of 0x7F into i.
If V is set, we go ahead and load 0x7F into i.
*/
"brvc L_%= \n\t"
"ldi %0, 0x7F \n\t"
"L_%=: "
: "+a" (i)
: "a" (j) );
return i;
#elif QADD7_ARM_DSP_ASM == 1
asm volatile( "qadd8 %0, %0, %1" : "+r" (i) : "r" (j));
return i;
#else
#error "No implementation for qadd7 available."
#endif
}
// qsub8: subtract one byte from another, saturating at 0x00
LIB8STATIC uint8_t qsub8( uint8_t i, uint8_t j)
{
#if QSUB8_C == 1
int t = i - j;
if( t < 0) t = 0;
return t;
#elif QSUB8_AVRASM == 1
asm volatile(
/* First, subtract j from i, conditioning the C flag */
"sub %0, %1 \n\t"
/* Now test the C flag.
If C is clear, we branch around a load of 0x00 into i.
If C is set, we go ahead and load 0x00 into i.
*/
"brcc L_%= \n\t"
"ldi %0, 0x00 \n\t"
"L_%=: "
: "+a" (i)
: "a" (j) );
return i;
#else
#error "No implementation for qsub8 available."
#endif
}
// add8: add one byte to another, with one byte result
LIB8STATIC uint8_t add8( uint8_t i, uint8_t j)
{
#if ADD8_C == 1
int t = i + j;
return t;
#elif ADD8_AVRASM == 1
// Add j to i, period.
asm volatile( "add %0, %1" : "+a" (i) : "a" (j));
return i;
#else
#error "No implementation for add8 available."
#endif
}
// sub8: subtract one byte from another, 8-bit result
LIB8STATIC uint8_t sub8( uint8_t i, uint8_t j)
{
#if SUB8_C == 1
int t = i - j;
return t;
#elif SUB8_AVRASM == 1
// Subtract j from i, period.
asm volatile( "sub %0, %1" : "+a" (i) : "a" (j));
return i;
#else
#error "No implementation for sub8 available."
#endif
}
// scale8: scale one byte by a second one, which is treated as
// the numerator of a fraction whose denominator is 256
// In other words, it computes i * (scale / 256)
// 4 clocks AVR, 2 clocks ARM
LIB8STATIC uint8_t scale8( uint8_t i, fract8 scale)
{
#if SCALE8_C == 1
return ((int)i * (int)(scale) ) >> 8;
#elif SCALE8_AVRASM == 1
asm volatile(
/* Multiply 8-bit i * 8-bit scale, giving 16-bit r1,r0 */
"mul %0, %1 \n\t"
/* Move the high 8-bits of the product (r1) back to i */
"mov %0, r1 \n\t"
/* Restore r1 to "0"; it's expected to always be that */
"clr __zero_reg__ \n\t"
: "+a" (i) /* writes to i */
: "a" (scale) /* uses scale */
: "r0", "r1" /* clobbers r0, r1 */ );
/* Return the result */
return i;
#else
#error "No implementation for scale8 available."
#endif
}
// The "video" version of scale8 guarantees that the output will
// be only be zero if one or both of the inputs are zero. If both
// inputs are non-zero, the output is guaranteed to be non-zero.
// This makes for better 'video'/LED dimming, at the cost of
// several additional cycles.
LIB8STATIC uint8_t scale8_video( uint8_t i, fract8 scale)
{
#if SCALE8_C == 1
uint8_t nonzeroscale = (scale != 0) ? 1 : 0;
uint8_t j = (i == 0) ? 0 : (((int)i * (int)(scale) ) >> 8) + nonzeroscale;
return j;
#elif SCALE8_AVRASM == 1
uint8_t nonzeroscale = (scale != 0) ? 1 : 0;
asm volatile(
" tst %0 \n"
" breq L_%= \n"
" mul %0, %1 \n"
" mov %0, r1 \n"
" add %0, %2 \n"
" clr __zero_reg__ \n"
"L_%=: \n"
: "+a" (i)
: "a" (scale), "a" (nonzeroscale)
: "r0", "r1");
// Return the result
return i;
#else
#error "No implementation for scale8_video available."
#endif
}
// This version of scale8 does not clean up the R1 register on AVR
// If you are doing several 'scale8's in a row, use this, and
// then explicitly call cleanup_R1.
LIB8STATIC uint8_t scale8_LEAVING_R1_DIRTY( uint8_t i, fract8 scale)
{
#if SCALE8_C == 1
return ((int)i * (int)(scale) ) >> 8;
#elif SCALE8_AVRASM == 1
asm volatile(
/* Multiply 8-bit i * 8-bit scale, giving 16-bit r1,r0 */
"mul %0, %1 \n\t"
/* Move the high 8-bits of the product (r1) back to i */
"mov %0, r1 \n\t"
/* R1 IS LEFT DIRTY HERE; YOU MUST ZERO IT OUT YOURSELF */
/* "clr __zero_reg__ \n\t" */
: "+a" (i) /* writes to i */
: "a" (scale) /* uses scale */
: "r0", "r1" /* clobbers r0, r1 */ );
// Return the result
return i;
#else
#error "No implementation for scale8_LEAVING_R1_DIRTY available."
#endif
}
// THIS FUNCTION ALWAYS MODIFIES ITS ARGUMENT DIRECTLY IN PLACE
LIB8STATIC void nscale8_LEAVING_R1_DIRTY( uint8_t& i, fract8 scale)
{
#if SCALE8_C == 1
i = ((int)i * (int)(scale) ) >> 8;
#elif SCALE8_AVRASM == 1
asm volatile(
/* Multiply 8-bit i * 8-bit scale, giving 16-bit r1,r0 */
"mul %0, %1 \n\t"
/* Move the high 8-bits of the product (r1) back to i */
"mov %0, r1 \n\t"
/* R1 IS LEFT DIRTY HERE; YOU MUST ZERO IT OUT YOURSELF */
/* "clr __zero_reg__ \n\t" */
: "+a" (i) /* writes to i */
: "a" (scale) /* uses scale */
: "r0", "r1" /* clobbers r0, r1 */ );
#else
#error "No implementation for nscale8_LEAVING_R1_DIRTY available."
#endif
}
LIB8STATIC uint8_t scale8_video_LEAVING_R1_DIRTY( uint8_t i, fract8 scale)
{
#if SCALE8_C == 1
uint8_t nonzeroscale = (scale != 0) ? 1 : 0;
uint8_t j = (i == 0) ? 0 : (((int)i * (int)(scale) ) >> 8) + nonzeroscale;
return j;
#elif SCALE8_AVRASM == 1
uint8_t nonzeroscale = (scale != 0) ? 1 : 0;
asm volatile(
" tst %0 \n"
" breq L_%= \n"
" mul %0, %1 \n"
" mov %0, r1 \n"
" add %0, %2 \n"
/* R1 IS LEFT DIRTY, YOU MUST ZERO IT OUT YOURSELF */
"L_%=: \n"
: "+a" (i)
: "a" (scale), "a" (nonzeroscale)
: "r0", "r1");
// Return the result
return i;
#else
#error "No implementation for scale8_video available."
#endif
}
LIB8STATIC void cleanup_R1()
{
#if CLEANUP_R1_AVRASM == 1
// Restore r1 to "0"; it's expected to always be that
asm volatile( "clr __zero_reg__ \n\t" : : : "r1" );
#endif
}
// nscale8x3: scale three one byte values by a fourth one, which is treated as
// the numerator of a fraction whose demominator is 256
// In other words, it computes r,g,b * (scale / 256)
//
// THIS FUNCTION ALWAYS MODIFIES ITS ARGUMENTS IN PLACE
LIB8STATIC void nscale8x3( uint8_t& r, uint8_t& g, uint8_t& b, fract8 scale)
{
#if SCALE8_C == 1
r = ((int)r * (int)(scale) ) >> 8;
g = ((int)g * (int)(scale) ) >> 8;
b = ((int)b * (int)(scale) ) >> 8;
#elif SCALE8_AVRASM == 1
r = scale8_LEAVING_R1_DIRTY(r, scale);
g = scale8_LEAVING_R1_DIRTY(g, scale);
b = scale8_LEAVING_R1_DIRTY(b, scale);
cleanup_R1();
#else
#error "No implementation for nscale8x3 available."
#endif
}
LIB8STATIC void nscale8x3_video( uint8_t& r, uint8_t& g, uint8_t& b, fract8 scale)
{
#if SCALE8_C == 1
uint8_t nonzeroscale = (scale != 0) ? 1 : 0;
r = (r == 0) ? 0 : (((int)r * (int)(scale) ) >> 8) + nonzeroscale;
g = (g == 0) ? 0 : (((int)g * (int)(scale) ) >> 8) + nonzeroscale;
b = (b == 0) ? 0 : (((int)b * (int)(scale) ) >> 8) + nonzeroscale;
#elif SCALE8_AVRASM == 1
r = scale8_video_LEAVING_R1_DIRTY( r, scale);
g = scale8_video_LEAVING_R1_DIRTY( g, scale);
b = scale8_video_LEAVING_R1_DIRTY( b, scale);
cleanup_R1();
#else
#error "No implementation for nscale8x3 available."
#endif
}
// nscale8x2: scale two one byte values by a third one, which is treated as
// the numerator of a fraction whose demominator is 256
// In other words, it computes i,j * (scale / 256)
//
// THIS FUNCTION ALWAYS MODIFIES ITS ARGUMENTS IN PLACE
LIB8STATIC void nscale8x2( uint8_t& i, uint8_t& j, fract8 scale)
{
#if SCALE8_C == 1
i = ((int)i * (int)(scale) ) >> 8;
j = ((int)j * (int)(scale) ) >> 8;
#elif SCALE8_AVRASM == 1
i = scale8_LEAVING_R1_DIRTY(i, scale);
j = scale8_LEAVING_R1_DIRTY(j, scale);
cleanup_R1();
#else
#error "No implementation for nscale8x2 available."
#endif
}
LIB8STATIC void nscale8x2_video( uint8_t& i, uint8_t& j, fract8 scale)
{
#if SCALE8_C == 1
uint8_t nonzeroscale = (scale != 0) ? 1 : 0;
i = (i == 0) ? 0 : (((int)i * (int)(scale) ) >> 8) + nonzeroscale;
j = (j == 0) ? 0 : (((int)j * (int)(scale) ) >> 8) + nonzeroscale;
#elif SCALE8_AVRASM == 1
i = scale8_video_LEAVING_R1_DIRTY( i, scale);
j = scale8_video_LEAVING_R1_DIRTY( j, scale);
cleanup_R1();
#else
#error "No implementation for nscale8x2 available."
#endif
}
// scale16by8: scale a 16-bit unsigned value by an 8-bit value,
// considered as numerator of a fraction whose denominator
// is 256. In other words, it computes i * (scale / 256)
#if SCALE16BY8_C == 1
LIB8STATIC uint16_t scale16by8( uint16_t i, fract8 scale )
{
uint16_t result;
result = (i * scale) / 256;
return result;
}
#elif SCALE16BY8_AVRASM == 1
LIB8STATIC uint16_t scale16by8( uint16_t i, fract8 scale )
{
uint16_t result;
asm volatile(
// result.A = HighByte(i.A x j )
" mul %A[i], %[scale] \n\t"
" mov %A[result], r1 \n\t"
" clr %B[result] \n\t"
// result.A-B += i.B x j
" mul %B[i], %[scale] \n\t"
" add %A[result], r0 \n\t"
" adc %B[result], r1 \n\t"
// cleanup r1
" clr __zero_reg__ \n\t"
: [result] "=r" (result)
: [i] "r" (i), [scale] "r" (scale)
: "r0", "r1"
);
return result;
}
#else
#error "No implementation for scale16by8 available."
#endif
// scale16: scale a 16-bit unsigned value by a 16-bit value,
// considered as numerator of a fraction whose denominator
// is 65536. In other words, it computes i * (scale / 65536)
#if SCALE16_C == 1
LIB8STATIC uint16_t scale16( uint16_t i, fract16 scale )
{
uint16_t result;
result = ((uint32_t)(i) * (uint32_t)(scale)) / 65536;
return result;
}
#elif SCALE16_AVRASM == 1
LIB8STATIC
uint16_t scale16( uint16_t i, fract16 scale )
{
uint32_t result = 0;
const uint8_t zero = 0;
asm volatile(
// result.A-B = i.A x scale.A
" mul %A[i], %A[scale] \n\t"
// save results...
// basic idea:
//" mov %A[result], r0 \n\t"
//" mov %B[result], r1 \n\t"
// which can be written as...
" movw %A[result], r0 \n\t"
// We actually need to do anything with r0,
// as result.A is never used again here, so we
// could just move the high byte, but movw is
// one clock cycle, just like mov, so might as
// well, in case we want to use this code for
// a generic 16x16 multiply somewhere.
// result.C-D = i.B x scale.B
" mul %B[i], %B[scale] \n\t"
//" mov %C[result], r0 \n\t"
//" mov %D[result], r1 \n\t"
" movw %C[result], r0 \n\t"
// result.B-D += i.B x scale.A
" mul %B[i], %A[scale] \n\t"
" add %B[result], r0 \n\t"
" adc %C[result], r1 \n\t"
" adc %D[result], %[zero] \n\t"
// result.B-D += i.A x scale.B
" mul %A[i], %B[scale] \n\t"
" add %B[result], r0 \n\t"
" adc %C[result], r1 \n\t"
" adc %D[result], %[zero] \n\t"
// cleanup r1
" clr r1 \n\t"
: [result] "+r" (result)
: [i] "r" (i),
[scale] "r" (scale),
[zero] "r" (zero)
: "r0", "r1"
);
result = result >> 16;
return result;
}
#else
#error "No implementation for scale16 available."
#endif
// mul8: 8x8 bit multiplication, with 8 bit result
LIB8STATIC uint8_t mul8( uint8_t i, uint8_t j)
{
#if MUL8_C == 1
return ((int)i * (int)(j) ) & 0xFF;
#elif MUL8_AVRASM == 1
asm volatile(
/* Multiply 8-bit i * 8-bit j, giving 16-bit r1,r0 */
"mul %0, %1 \n\t"
/* Extract the LOW 8-bits (r0) */
"mov %0, r0 \n\t"
/* Restore r1 to "0"; it's expected to always be that */
"clr __zero_reg__ \n\t"
: "+a" (i)
: "a" (j)
: "r0", "r1");
return i;
#else
#error "No implementation for mul8 available."
#endif
}
// mul8: saturating 8x8 bit multiplication, with 8 bit result
LIB8STATIC uint8_t qmul8( uint8_t i, uint8_t j)
{
#if QMUL8_C == 1
int p = ((int)i * (int)(j) );
if( p > 255) p = 255;
return p;
#elif QMUL8_AVRASM == 1
asm volatile(
/* Multiply 8-bit i * 8-bit j, giving 16-bit r1,r0 */
" mul %0, %1 \n\t"
/* If high byte of result is zero, all is well. */
" tst r1 \n\t"
" breq Lnospill_%= \n\t"
/* If high byte of result > 0, saturate low byte to 0xFF */
" ldi %0,0xFF \n\t"
" rjmp Ldone_%= \n\t"
"Lnospill_%=: \n\t"
/* Extract the LOW 8-bits (r0) */
" mov %0, r0 \n\t"
"Ldone_%=: \n\t"
/* Restore r1 to "0"; it's expected to always be that */
" clr __zero_reg__ \n\t"
: "+a" (i)
: "a" (j)
: "r0", "r1");
return i;
#else
#error "No implementation for qmul8 available."
#endif
}
// abs8: take abs() of a signed 8-bit uint8_t
LIB8STATIC int8_t abs8( int8_t i)
{
#if ABS8_C == 1
if( i < 0) i = -i;
return i;
#elif ABS8_AVRASM == 1
asm volatile(
/* First, check the high bit, and prepare to skip if it's clear */
"sbrc %0, 7 \n"
/* Negate the value */
"neg %0 \n"
: "+r" (i) : "r" (i) );
return i;
#else
#error "No implementation for abs8 available."
#endif
}
///////////////////////////////////////////////////////////////////////
//
// float-to-fixed and fixed-to-float conversions
//
// Note that anything involving a 'float' on AVR will be slower.
// floatToSfract15: conversion from IEEE754 float in the range (-1,1)
// to 16-bit fixed point. Note that the extremes of
// one and negative one are NOT representable. The
// representable range is basically
//
// sfract15ToFloat: conversion from sfract15 fixed point to
// IEEE754 32-bit float.
LIB8STATIC
float sfract15ToFloat( sfract15 y)
{
return y / 32768.0;
}
LIB8STATIC
sfract15 floatToSfract15( float f)
{
return f * 32768.0;
}
///////////////////////////////////////////////////////////////////////
// Dimming and brightening functions
//
// The eye does not respond in a linear way to light.
// High speed PWM'd LEDs at 50% duty cycle appear far
// brighter then the 'half as bright' you might expect.
//
// If you want your midpoint brightness leve (128) to
// appear half as bright as 'full' brightness (255), you
// have to apply a 'dimming function'.
//
//
LIB8STATIC uint8_t dim8_raw( uint8_t x)
{
return scale8( x, x);
}
LIB8STATIC uint8_t dim8_video( uint8_t x)
{
return scale8_video( x, x);
}
LIB8STATIC uint8_t brighten8_raw( uint8_t x)
{
uint8_t ix = 255 - x;
return 255 - scale8( ix, ix);
}
LIB8STATIC uint8_t brighten8_video( uint8_t x)
{
uint8_t ix = 255 - x;
return 255 - scale8_video( ix, ix);
}
///////////////////////////////////////////////////////////////////////
// A 16-bit PNRG good enough for LED animations
// X(n+1) = (2053 * X(n)) + 13849)
#define RAND16_2053 2053
#define RAND16_13849 13849
extern uint16_t rand16seed;// = RAND16_SEED;
LIB8STATIC uint8_t random8()
{
rand16seed = (rand16seed * RAND16_2053) + RAND16_13849;
return rand16seed;
}
LIB8STATIC uint16_t random16()
{
rand16seed = (rand16seed * RAND16_2053) + RAND16_13849;
return rand16seed;
}
LIB8STATIC uint8_t random8(uint8_t lim)
{
uint8_t r = random8();
r = scale8( r, lim);
return r;
}
LIB8STATIC uint8_t random8(uint8_t min, uint8_t lim)
{
uint8_t delta = lim - min;
uint8_t r = random8(delta) + min;
return r;
}
LIB8STATIC uint16_t random16( uint16_t lim)
{
uint16_t r = random16();
uint32_t p = (uint32_t)lim * (uint32_t)r;
r = p >> 16;
return r;
}
LIB8STATIC uint16_t random16( uint16_t min, uint16_t lim)
{
uint16_t delta = lim - min;
uint16_t r = random16( delta) + min;
return r;
}
LIB8STATIC void random16_set_seed( uint16_t seed)
{
rand16seed = seed;
}
LIB8STATIC uint16_t random16_get_seed()
{
return rand16seed;
}
LIB8STATIC void random16_add_entropy( uint16_t entropy)
{
rand16seed += entropy;
}
///////////////////////////////////////////////////////////////////////
// sin16 & cos16:
// Fast 16-bit approximations of sin(x) & cos(x).
// Input angle is an unsigned int from 0-65535.
// Output is signed int from -32767 to 32767.
//
// This approximation never varies more than 0.69%
// from the floating point value you'd get by doing
// float s = sin( x ) * 32767.0;
//
// Don't use this approximation for calculating the
// trajectory of a rocket to Mars, but it's great
// for art projects and LED displays.
//
// On Arduino/AVR, this approximation is more than
// 10X faster than floating point sin(x) and cos(x)