You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
198 lines
6.3 KiB
198 lines
6.3 KiB
/* ReceiverFM.ino Bob Larkin 26 April 2020
|
|
* No copyright.
|
|
*
|
|
* This INO runs the FM detector on input data from the Codec. It
|
|
* requires an FM modulated signal source at 15 kHz. The Serial out is
|
|
* the squelch level generated by the squelch noise detector.
|
|
*
|
|
* Commented out is a test of introducing a sine wave to the
|
|
* FM Detector and taking 512 samples of the output. It is
|
|
* a static test with a fixed frequency for test and so
|
|
* the output DC value and noise can be tested. Note that the 512
|
|
* samples include the startup transient, so the first 300,
|
|
* or so, points should be ignored in seeing the DC value.
|
|
*
|
|
* An option is to change the squelch noise filter (commented out)
|
|
* and this serves as an example of changing the 10 coefficients.
|
|
*
|
|
* Another commented out loop code will print the observed spectrum using
|
|
* the 1024 point FFT. This shows the NBFM de-emphasis curve.
|
|
*
|
|
* Change the value of sine1.frequency to see the DC output change.
|
|
* See FMReceiver2.ino for testing with real AC modulation.
|
|
*
|
|
* As an alternative the input can come from the ADC for "SINE_ADC 0"
|
|
*
|
|
* Output is sent to left channel SGTL5000 DAC.
|
|
*/
|
|
|
|
#include "Audio.h"
|
|
#include <OpenAudio_ArduinoLibrary.h>
|
|
|
|
// SINE_ADC 1 for internally generated sine wave.
|
|
// SINE_ADC 0 to use the SGTL5000 Teensy audio adaptor ADC/DAC
|
|
#define SINE_ADC 0
|
|
|
|
#if SINE_ADC
|
|
AudioSynthGaussian_F32 gwn1;
|
|
AudioSynthWaveformSine_F32 sine1;
|
|
AudioMixer4_F32 mix1;
|
|
RadioFMDetector_F32 fmDet1;
|
|
AudioOutputI2S_F32 i2sOut;
|
|
AudioAnalyzeFFT1024_F32 fft1;
|
|
AudioRecordQueue_F32 queue1;
|
|
AudioControlSGTL5000 sgtl5000_1;
|
|
AudioConnection_F32 connectA(gwn1, 0, mix1, 0);
|
|
AudioConnection_F32 connectB(sine1, 0, mix1, 1);
|
|
AudioConnection_F32 connectC(mix1, 0, fmDet1, 0);
|
|
#else // Input from Teensy Audio Adaptor SGTL5000
|
|
// Note - With no input, the FM detector output is all noise. This
|
|
// can be loud, so lower the gain below (like 0.05 gain).
|
|
AudioInputI2S_F32 i2sIn;
|
|
RadioFMDetector_F32 fmDet1;
|
|
AudioAnalyzeFFT1024_F32 fft1;
|
|
AudioRecordQueue_F32 queue1;
|
|
AudioOutputI2S_F32 i2sOut;
|
|
AudioControlSGTL5000 sgtl5000_1;
|
|
AudioConnection_F32 connectD(i2sIn, 0, fmDet1, 0); // left
|
|
#endif
|
|
// Common for both input sources
|
|
AudioConnection_F32 connect1(fmDet1, 1, i2sOut, 0); // Squelched
|
|
AudioConnection_F32 connect2(fmDet1, 0, fft1, 0);
|
|
AudioConnection_F32 connect3(fmDet1, 0, queue1, 0);
|
|
|
|
float dt1[512]; // Place to save output
|
|
float *pq1, *pd1;
|
|
uint16_t k;
|
|
int i;
|
|
|
|
void setup(void) {
|
|
AudioMemory(5);
|
|
AudioMemory_F32(100);
|
|
Serial.begin(300); delay(500); // Any rate is OK
|
|
Serial.println("Serial Started");
|
|
|
|
sgtl5000_1.enable();
|
|
sgtl5000_1.inputSelect(AUDIO_INPUT_LINEIN);
|
|
|
|
#if SINE_ADC
|
|
sine1.frequency(15000.0);
|
|
sine1.amplitude(0.0001f);
|
|
gwn1.amplitude(0.1f);
|
|
#endif
|
|
|
|
fft1.setOutputType(FFT_DBFS);
|
|
fft1.setNAverage(10);
|
|
|
|
// The FM detector has error checking during object construction
|
|
// when Serial.print is not available. See RadioFMDetector_F32.h:
|
|
Serial.print("FM Initialization errors: ");
|
|
Serial.println( fmDet1.returnInitializeFMError() );
|
|
|
|
// The following enables error checking inside of the "ubdate()"
|
|
// Output goes to the Serial (USB) Monitor. Normally, this is quiet.
|
|
fmDet1.showError(1);
|
|
|
|
fmDet1.setSquelchThreshold(0.7f);
|
|
|
|
// Here is an example of designing and using a non-default squelch
|
|
// noise filter. The INO provides storage for the new coefficients.
|
|
// static float newFilter[10];
|
|
// freq Q ptr to Coeff
|
|
// setBandpassBiQuad(2000.0f, 3.0f, &newFilter[0]);
|
|
// setBandpassBiQuad(4000.0f, 3.0f, &newFilter[5]);
|
|
// fmDet1.setSquelchFilter(newFilter);
|
|
|
|
// Set the volume control (0.0 to 1.0)
|
|
i2sOut.setGain(0.05f);
|
|
|
|
queue1.begin();
|
|
i = 0; k=0;
|
|
}
|
|
|
|
void loop(void) {
|
|
float lData[512];
|
|
|
|
Serial.print("sqLevel "); Serial.println(fmDet1.getSquelchLevel(), 6);
|
|
delay(500);
|
|
|
|
/*
|
|
if( fft1.available() ) {
|
|
float* pd = fft1.getData();
|
|
for(int k=0; k<512; k++)
|
|
lData[k] = pd[k];
|
|
for(int k=0; k<512; k++)
|
|
Serial.println(lData[k],3);
|
|
Serial.println(" -------");
|
|
}
|
|
*/
|
|
|
|
/*
|
|
// Collect 512 samples and output to Serial
|
|
// This "if" will be active for i = 0,1,2,3
|
|
if (queue1.available() >= 1) {
|
|
if( i>=0 && i<4) {
|
|
pq1 = queue1.readBuffer();
|
|
pd1 = &dt1[i*128];
|
|
for(k=0; k<128; k++)
|
|
*pd1++ = *pq1++;
|
|
queue1.freeBuffer();
|
|
if(i++==3) {
|
|
i=4; // Only collect 4 blocks
|
|
queue1.end(); // No more data to queue1
|
|
}
|
|
}
|
|
else {
|
|
queue1.freeBuffer();
|
|
}
|
|
}
|
|
// We have 512 data samples. Serial.print them
|
|
if(i == 4) {
|
|
#if SINE_ADC
|
|
Serial.println("For 14,000 Hz sine wave input:");
|
|
#endif
|
|
Serial.println("512 samples of FM Det output, starting t=0");
|
|
Serial.println("Time in sec, FM Output, Dev from 15,000 Hz:");
|
|
for (k=0; k<512; k++) {
|
|
Serial.print (0.000022667*(float32_t)k, 6); Serial.print (", ");
|
|
Serial.print (dt1[k],7); Serial.print (", ");
|
|
Serial.println (dt1[k]/0.000142421, 2); // Convert to Hz
|
|
}
|
|
i = 5;
|
|
}
|
|
if(i==5) {
|
|
i = 6;
|
|
Serial.print("CPU: Percent Usage, Max: ");
|
|
Serial.print(AudioProcessorUsage());
|
|
Serial.print(", ");
|
|
Serial.println(AudioProcessorUsageMax());
|
|
|
|
Serial.print("Int16 Memory Usage, Max: ");
|
|
Serial.print(AudioMemoryUsage());
|
|
Serial.print(", ");
|
|
Serial.println(AudioMemoryUsageMax());
|
|
|
|
Serial.print("Float Memory Usage, Max: ");
|
|
Serial.print(AudioMemoryUsage_F32());
|
|
Serial.print(", ");
|
|
Serial.println(AudioMemoryUsageMax_F32());
|
|
Serial.println();
|
|
}
|
|
*/
|
|
}
|
|
|
|
// Find BiQuad Coefficients for Squelch Noise filter.
|
|
// Only used if the default -6 dB points of 2680 and 4420 Hz
|
|
// are not suitable
|
|
void setBandpassBiQuad(float frequency, float q, float* cf) {
|
|
double w0 = frequency * (2 * 3.141592654 / 44100); // sampleRate_Hz);
|
|
double sinW0 = sin(w0);
|
|
double alpha = sinW0 / ((double)q * 2.0);
|
|
double cosW0 = cos(w0);
|
|
double scale = 1.0 / (1.0+alpha);
|
|
/* b0 */ cf[0] = alpha * scale;
|
|
/* b1 */ cf[1] = 0;
|
|
/* b2 */ cf[2] = (-alpha) * scale;
|
|
/* a1 */ cf[3] = -(-2.0 * cosW0) * scale;
|
|
/* a2 */ cf[4] = -(1.0 - alpha) * scale;
|
|
}
|
|
|