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ADD: added a simple averging filter function. input parameter K, can be 1 to 8

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ref: http://www.edn.com/design/systems-design/4320010/A-simple-software-lowpass-filter-suits-embedded-system-applications
This commit is contained in:
iceman1001 2016-08-29 20:29:31 +02:00
commit 4c543dbd3f
3 changed files with 37 additions and 7 deletions
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5
client/cmddata.c
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@ -2417,7 +2417,10 @@ int Cmdhex2bin(const char *Cmd)
} }
int CmdDataIIR(const char *Cmd){ int CmdDataIIR(const char *Cmd){
iceIIR_Butterworth(GraphBuffer, GraphTraceLen);
uint8_t k = param_get8(Cmd,0);
//iceIIR_Butterworth(GraphBuffer, GraphTraceLen);
iceSimple_Filter(GraphBuffer, GraphTraceLen, k);
RepaintGraphWindow(); RepaintGraphWindow();
return 0; return 0;
} }

32
client/ui.c
View file

@ -85,9 +85,13 @@ void iceIIR_Butterworth(int *data, const size_t len){
int i,j; int i,j;
int * output = (int* ) malloc(sizeof(int) * len); int * output = (int* ) malloc(sizeof(int) * len);
if ( !output ) return;
// clear mem
memset(output, 0x00, len); memset(output, 0x00, len);
float fc = 0.1125f; // center frequency
size_t adjustedLen = len; size_t adjustedLen = len;
float fc = 0.1125f; // center frequency
// create very simple low-pass filter to remove images (2nd-order Butterworth) // create very simple low-pass filter to remove images (2nd-order Butterworth)
float complex iir_buf[3] = {0,0,0}; float complex iir_buf[3] = {0,0,0};
@ -98,7 +102,7 @@ void iceIIR_Butterworth(int *data, const size_t len){
float complex x_prime = 1.0f; // save sample for estimating frequency float complex x_prime = 1.0f; // save sample for estimating frequency
float complex x; float complex x;
for (i=0; i<adjustedLen; ++i) { for (i = 0; i < adjustedLen; ++i) {
sample = data[i]; sample = data[i];
@ -118,16 +122,38 @@ void iceIIR_Butterworth(int *data, const size_t len){
float freq = cargf(x*conjf(x_prime)); float freq = cargf(x*conjf(x_prime));
x_prime = x; // retain this sample for next iteration x_prime = x; // retain this sample for next iteration
output[i] =(freq > 0)? 10 : -10; output[i] =(freq > 0) ? 127 : -127;
} }
// show data // show data
//memcpy(data, output, adjustedLen);
for (j=0; j<adjustedLen; ++j) for (j=0; j<adjustedLen; ++j)
data[j] = output[j]; data[j] = output[j];
free(output); free(output);
} }
void iceSimple_Filter(int *data, const size_t len, uint8_t k){
// ref: http://www.edn.com/design/systems-design/4320010/A-simple-software-lowpass-filter-suits-embedded-system-applications
// parameter K
#define FILTER_SHIFT 4
int32_t filter_reg = 0;
int16_t input, output;
int8_t shift = (k <=8 ) ? k : FILTER_SHIFT;
for (int i = 0; i < len; ++i){
input = data[i];
// Update filter with current sample
filter_reg = filter_reg - (filter_reg >> shift) + input;
// Scale output for unity gain
output = filter_reg >> shift;
data[i] = output;
}
}
float complex cexpf (float complex Z) float complex cexpf (float complex Z)
{ {
float complex Res; float complex Res;

1
client/ui.h
View file

@ -42,4 +42,5 @@ extern int offline;
extern int flushAfterWrite; //buzzy extern int flushAfterWrite; //buzzy
void iceIIR_Butterworth(int * data, const size_t len); void iceIIR_Butterworth(int * data, const size_t len);
void iceSimple_Filter(int *data, const size_t len, uint8_t k);
#endif #endif