logfilename = fn;
}
-void iceFsk3(int * data, const size_t len){
+void iceIIR_Butterworth(int *data, const size_t len){
int i,j;
int * output = (int* ) malloc(sizeof(int) * len);
+ if ( !output ) return;
+
+ // clear mem
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)
float complex iir_buf[3] = {0,0,0};
float b[3] = {0.003621681514929, 0.007243363029857, 0.003621681514929};
float a[3] = {1.000000000000000, -1.822694925196308, 0.837181651256023};
- float sample = 0; // input sample read from file
+ float sample = 0; // input sample read from array
float complex x_prime = 1.0f; // save sample for estimating frequency
float complex x;
- for (i=0; i<adjustedLen; ++i) {
+ for (i = 0; i < adjustedLen; ++i) {
- sample = data[i]+128;
+ sample = data[i];
// remove DC offset and mix to complex baseband
x = (sample - 127.5f) * cexpf( _Complex_I * 2 * M_PI * fc * i );
float freq = cargf(x*conjf(x_prime));
x_prime = x; // retain this sample for next iteration
- output[i] =(freq > 0)? 10 : -10;
+ output[i] =(freq > 0) ? 127 : -127;
}
// show data
+ //memcpy(data, output, adjustedLen);
for (j=0; j<adjustedLen; ++j)
data[j] = output[j];
-
- CmdLtrim("30");
- adjustedLen -= 30;
-
- // zero crossings.
- for (j=0; j<adjustedLen; ++j){
- if ( data[j] == 10) break;
- }
- int startOne =j;
-
- for (;j<adjustedLen; ++j){
- if ( data[j] == -10 ) break;
- }
- int stopOne = j-1;
-
- int fieldlen = stopOne-startOne;
-
- fieldlen = (fieldlen == 39 || fieldlen == 41)? 40 : fieldlen;
- fieldlen = (fieldlen == 59 || fieldlen == 51)? 50 : fieldlen;
- if ( fieldlen != 40 && fieldlen != 50){
- printf("Detected field Length: %d \n", fieldlen);
- printf("Can only handle 40 or 50. Aborting...\n");
- free(output);
- return;
- }
-
- // FSK sequence start == 000111
- int startPos = 0;
- for (i =0; i<adjustedLen; ++i){
- int dec = 0;
- for ( j = 0; j < 6*fieldlen; ++j){
- dec += data[i + j];
- }
- if (dec == 0) {
- startPos = i;
- break;
- }
- }
- printf("000111 position: %d \n", startPos);
+ free(output);
+}
- startPos += 6*fieldlen+5;
-
- int bit =0;
- printf("BINARY\n");
- printf("R/40 : ");
- for (i =startPos ; i < adjustedLen; i += 40){
- bit = data[i]>0 ? 1:0;
- printf("%d", bit );
+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;
}
- printf("\n");
-
- printf("R/50 : ");
- for (i =startPos ; i < adjustedLen; i += 50){
- bit = data[i]>0 ? 1:0;
- printf("%d", bit ); }
- printf("\n");
-
- free(output);
}
float complex cexpf (float complex Z)