robin/two_pole_dc_pass
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Strong double prec low pass added

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This commit is contained in:
Robin. P. Clark 2019-09-11 12:29:36 +01:00
parent 8bd3e66be3
commit cc1c2d1a95
2 changed files with 38 additions and 5 deletions
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7
tp.gpt
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@ -1,6 +1,11 @@
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 1:6 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, \
"tp.dat" using 1:21 title "double prec lp" 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"

36
two_pole_7_8.c
View File

@ -289,6 +289,32 @@ int zero_only_4 ( int input )
}
// 1/16 is 0.625
//
// A double precision two pole filter could be used in a higher level
// to further smooth readings
#define DOUBLE_FILTER_PARAM 0.01
#define DOUBLE_FILTER_PARAM_LAG (1.0 - DOUBLE_FILTER_PARAM)
int16_t /* squared version of LAG 0.01 0.99 */
two_pole_double_low_pass ( int16_t input ) {
static double x0, y1, y2;
static double res;
x0 = input;
res = x0 * (DOUBLE_FILTER_PARAM * DOUBLE_FILTER_PARAM);
res += y1 * 2.0 * DOUBLE_FILTER_PARAM_LAG;
res -= y2 * (DOUBLE_FILTER_PARAM_LAG * DOUBLE_FILTER_PARAM_LAG);
y2 = y1;
y1 = res;
return (int16_t) res + 0.5;
}
// This was initially tested at 1500 TDS with \pm 500 noise
// Tests at 15000 with \pm 1500 noise at BINFRACS 9 caused instability in the two pole 15 16
// BINFRACS down to 2 for that filter.
@ -303,7 +329,7 @@ int zero_only_4 ( int input )
int main () {
int i, zo2,zo3,zo4;
int16_t val,res, res34, res78, res78_2, rr, res_1516;
int16_t val,res, res34, res78, res78_2, rr, res_1516, tpdlp, tpdlp_1516;
for (i=0;i<1000;i++) {
@ -327,14 +353,16 @@ int main () {
zo2 = two_pole_7_8_zg(val); // zero_only_2 (val);
zo3 = zero_only_3 (val);
zo4 = zero_only_4 (val);
tpdlp = two_pole_double_low_pass ( val );
tpdlp_1516 = two_pole_double_low_pass (res_1516); // as fed by the yellow trace
res34 = (((res34<<2) - res34)>>2) + (val>>2);
res78 = (((res78<<3) - res78)>>3) + (val>>3);
res78_2 = (((res78_2<<3) - res78_2)>>3) + (res78>>3); // feed res78 into another should be the same as two pole
// 1 3 5 7 9 11 13 15 17 19
printf ("%d val %d res %d res34 %d res78 %d res78_2 %d res_1516 %d zo2 %d zo3 %d zo4 %d EOL\n",
i, val,res, res34, res78, res78_2, res_1516, zo2, zo3, zo4);
// 1 3 5 7 9 11 13 15 17 19 21
printf ("%d val %d res %d res34 %d res78 %d res78_2 %d res_1516 %d zo2 %d zo3 %d zo4 %d tpdlp_1516 %dEOL\n",
i, val,res, res34, res78, res78_2, res_1516, zo2, zo3, zo4, tpdlp_1516);
}