robin/two_pole_dc_pass
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15 16 squared lag filter now ready for 8 bit compiler

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maybe BINFRACS is a higher than it needs to be.
This commit is contained in:
Robin. P. Clark 2019-09-10 10:53:17 +01:00
parent 2647f7e4d4
commit 7562cf3246
2 changed files with 42 additions and 17 deletions
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13
tp.gpt
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@ -1,9 +1,16 @@
#plot "tp.dat" using 1:3 title "input", "tp.dat" using 1:5 title "two pole", "tp.dat" using 1:6 title "34LAG", "tp.dat" using 1:7 title "78LAG"
plot "tp.dat" using 1:3 title "input" with linespoints, "tp.dat" using 1:5 title "two pole" with linespoints, "tp.dat" using 1:6 title "34LAG" with linespoints, "tp.dat" using 1:7 title "78LAG" with linespoints, "tp.dat" using 1:13 title "two pole 15 16" with linespoints
#plot "tp.dat" using 1:3 title "input" with linespoints, "tp.dat" using 1:5 title "two pole" with linespoints, "tp.dat" using 1:7 title "78LAG" with linespoints, "tp.dat" using 1:9 title "78LAG TWICE" with linespoints, "tp.dat" using 1:11 title "two pole 15 16"
plot "tp.dat" using 1:3 title "input" with linespoints, "tp.dat" using 1:5 title "two pole" with linespoints, "tp.dat" using 1:11 title "two pole 15 16" with linespoints, "tp.dat" using 1:13 title "zero only" with linespoints
plot "tp.dat" using 1:3 title "input" with linespoints, "tp.dat" using 1:5 title "two pole" with linespoints, "tp.dat" using 1:15 title "7 8 two pole ZG" with linespoints, "tp.dat" using 1:17 title "zero only^3" with linespoints,"tp.dat" using 1:19 title "zero only^4" with linespoints
#
#
#plot "tp.dat" using 1:3 title "input" with linespoints, "tp.dat" using 1:5 title "two pole" with linespoints, "tp.dat" using 1:13 title "two pole 15 16" with linespoints
#plot "tp.dat" using 1:3 title "input" with linespoints, "tp.dat" using 1:5 title "two pole" with linespoints, "tp.dat" using 1:15 title "7 8 two pole ZG" with linespoints, "tp.dat" using 1:17 title "zero only^3" with linespoints,"tp.dat" using 1:19 title "zero only^4" with linespoints
!sleep 10
!sleep 10

46
two_pole_7_8.c
View File

@ -86,7 +86,7 @@ two_pole_7_8 ( int16_t input ) {
int16_t /* squared version of LAG_7_8 */
two_pole_7_8_zg ( int16_t input ) { // with zero guard
static int32_t y1=0,y2=0, x1,x2;
static int32_t y1=0,y2=0, x1,x2,x3,x4,x5,x6,x7,x8;
int32_t * res;
int32_t y0;
@ -107,8 +107,10 @@ two_pole_7_8_zg ( int16_t input ) { // with zero guard
// y0 = x0 + (14.0 / 8.0) * (double) y1 - (49.0/64.0) * (double) y2;
y0 = (x0>>1) + (x0>>2) + (x0>>6) + (x2>>1) + // 49/64 * x0 + 1/2 * x2
// (z-j)(z+j) zeros at half nyquist (Z^2 + 1) x0 + x2
y0 = //(x0>>1) + (x2>>1) +
(x0+x1+x2+x3) +
//(x0>>1) + (x0>>2) + (x0>>6) + (x2>>1) + // 49/64 * x0 + 1/2 * x2
// (14.0 / 8.0) * (double) y1
// this is 7/4
y1 + y1 - (y1>>2)
@ -130,6 +132,8 @@ two_pole_7_8_zg ( int16_t input ) { // with zero guard
y2 = y1;
y1 = y0;
x4 = x3;
x3 = x2;
x2 = x1;
x1 = x0;
@ -146,7 +150,7 @@ two_pole_7_8_zg ( int16_t input ) { // with zero guard
// this is a 64 bit machine (the pi)
//
int16_t /* squared version of LAG_7_8 */
int16_t /* squared version of LAG_15_16 */
two_pole_15_16 ( int16_t input ) {
static int32_t y1=0,y2=0, x1, x2;
@ -155,31 +159,45 @@ two_pole_15_16 ( int16_t input ) {
int32_t x0 = input;
// x0 times 0.125
// the minus 3 divides by 8 : DOUBLE POLE
x0 <<= (BIN_FRACS_15_16) ; // now all calculations are done times BIN_FRACS^2
y0 = x0 +
// (30.0 / 16.0) * (double) y1
// this is 7/8
//
// this is 7/8 which is 2 * 15/16...
y1 + y1 - (y1>>3)
//
//
// - (49.0/64.0) * (double) y2;
//
- ( (y2>>1) + // half
(y2>>2) + // quarter
(y2>>3) + // eighth
(y2>>8) // 256th
);
;
//- ( (y2>>1) + // half
// (y2>>2) + // quarter
// (y2>>3) + // eighth
// (y2>>8) // 256th
// );
//
// try to do the shfts in a way effecient for the HYTEC PIC18 compiler
//
y2>>=1;
y0 -= y2;
y2>>=1;
y0 -= y2;
y2>>=1;
y0 -= y2;
y2>>=5;
y0 -= y2;
y2 = y1;
y1 = y0;
// gain of the filter is 256 ((1/16)^2) if x0 is allowed in withiout pre-dividing
// gain of the filter is 256 ((1/16)^2) if x0 is allowed in without pre-dividing
//
y0 >>= 8;