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179 lines
7.2 KiB
179 lines
7.2 KiB
/* FreqShifter_FD_OA.ino
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*
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* Demonstrate frequency shifting via frequency domain processin.
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*
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* Created: Chip Audette (OpenAudio) Aug 2019
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*
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* Approach: This processing is performed in the frequency domain.
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* Frequencies can only be shifted by an integer number of bins,
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* so small frequency shifts are not possible. For example, for
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* a sample rate of 44.1kHz, and when using N=256, one can only
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* shift frequencies in multiples of 44.1/256 = 172.3 Hz.
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*
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* This processing is performed in the frequency domain where
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* we take the FFT, shift the bins upward or downward, take
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* the IFFT, and listen to the results. In effect, this is
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* single sideband modulation, which will sound very unnatural
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* (like robot voices!). Maybe you'll like it, or maybe not.
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* Probably not, unless you like weird. ;)
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*
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* You can shift frequencies upward or downward with this algorithm.
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*
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* Frequency Domain Processing:
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* * Take samples in the time domain
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* * Take FFT to convert to frequency domain
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* * Manipulate the frequency bins to do the freqyebct shifting
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* * Take IFFT to convert back to time domain
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* * Send samples back to the audio interface
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*
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* Built for the Tympan library for Teensy 3.6-based hardware
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*
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* Convert to Open Audio Bob Larkin June 2020
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* Tested OK for Teensy 3.6 and 4.0.
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* For settings:
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* sample rate (Hz) = 44117.00
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* block size (samples) = 128
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* N_FFT = 512
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* the following resources were used for Teensy 3.6
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* CPU Cur/Peak: 50.02%/50.24%
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* MEM Float32 Cur/Peak: 8/9
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* MEM Int16 Cur/Peak: 3/5
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* For Teensy 4.0:
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* CPU Cur/Peak: 6.53%/6.84%
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* MEM Float32 Cur/Peak: 8/9
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* MEM Int16 Cur/Peak: 3/4
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*
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* MIT License. Use at your own risk.
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*/
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#include "Audio.h"
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#include "AudioStream_F32.h"
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#include "OpenAudio_ArduinoLibrary.h"
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#include "SerialManager_FreqShift_OA.h"
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//set the sample rate and block size
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const float sample_rate_Hz = 44117.f; ; // other frequencies in the table in AudioOutputI2S_F32 for T3.x only
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const int audio_block_samples = 128; //for freq domain processing, a power of 2: 16, 32, 64, 128
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AudioSettings_F32 audio_settings(sample_rate_Hz, audio_block_samples);
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//create audio library objects for handling the audio
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AudioInputI2S i2sIn; // This I16 input/output is T4.x compatible
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AudioConvert_I16toF32 cnvrt1; // Convert to float
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AudioEffectFreqShiftFD_OA_F32 freqShift(audio_settings); // the frequency-domain processing block
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AudioEffectGain_F32 gain1; //Applies digital gain to audio data.
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AudioConvert_F32toI16 cnvrt2;
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AudioOutputI2S i2sOut;
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AudioControlSGTL5000 codec;
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//Make all of the audio connections
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AudioConnection patchCord1(i2sIn, 0, cnvrt1, 0); // connect to Left codec, 16-bit
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AudioConnection_F32 patchCord2(cnvrt1, 0, freqShift, 0);
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AudioConnection_F32 patchCord3(freqShift, 0, gain1, 0); //connect to gain
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AudioConnection_F32 patchCord4(gain1, 0, cnvrt2, 0); //connect to the left output
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AudioConnection patchCord6(cnvrt2, 0, i2sOut, 0);
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//control display and serial interaction
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bool enable_printCPUandMemory = false;
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void togglePrintMemoryAndCPU(void) { enable_printCPUandMemory = !enable_printCPUandMemory; };
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SerialManagerFreqShift_OA serialMgr;
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//inputs and levels
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float input_gain_dB = 15.0f; //gain on the microphone
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float vol_knob_gain_dB = 0.0; //will be overridden by volume knob
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// *************** SETUP **********************************
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void setup() {
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Serial.begin(1); delay(1000);
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Serial.println("freqShifter: starting setup()...");
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Serial.print(" : sample rate (Hz) = "); Serial.println(audio_settings.sample_rate_Hz);
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Serial.print(" : block size (samples) = "); Serial.println(audio_settings.audio_block_samples);
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// Audio connections require memory to work. For more
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// detailed information, see the MemoryAndCpuUsage example
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AudioMemory(10); // I16 type
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AudioMemory_F32(40, audio_settings);
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// Configure the FFT parameters algorithm
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int overlap_factor = 4; //set to 2, 4 or 8...which yields 50%, 75%, or 87.5% overlap (8x)
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int N_FFT = audio_block_samples * overlap_factor;
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Serial.print(" : N_FFT = "); Serial.println(N_FFT);
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freqShift.setup(audio_settings, N_FFT); //do after AudioMemory_F32();
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//configure the frequency shifting
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float shiftFreq_Hz = 750.0; //shift audio upward a bit
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float Hz_per_bin = audio_settings.sample_rate_Hz / ((float)N_FFT);
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int shift_bins = (int)(shiftFreq_Hz / Hz_per_bin + 0.5); //round to nearest bin
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shiftFreq_Hz = shift_bins * Hz_per_bin;
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Serial.print("Setting shift to "); Serial.print(shiftFreq_Hz);
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Serial.print(" Hz, which is "); Serial.print(shift_bins);
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Serial.println(" bins");
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freqShift.setShift_bins(shift_bins); //0 is no ffreq shifting.
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//Enable the Tympan to start the audio flowing!
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codec.enable();
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codec.adcHighPassFilterEnable();
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codec.inputSelect(AUDIO_INPUT_LINEIN);
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//finish the setup by printing the help menu to the serial connections
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serialMgr.printHelp();
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}
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// ************************* LOOP ****************************
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void loop() {
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//respond to Serial commands
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while (Serial.available()) serialMgr.respondToByte((char)Serial.read()); //USB Serial
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//check to see whether to print the CPU and Memory Usage
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if (enable_printCPUandMemory) printCPUandMemory(millis(), 3000); //print every 3000 msec
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} //end loop();
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//This routine prints the current and maximum CPU usage and the current usage of the AudioMemory that has been allocated
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void printCPUandMemory(unsigned long curTime_millis, unsigned long updatePeriod_millis) {
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//static unsigned long updatePeriod_millis = 3000; //how many milliseconds between updating gain reading?
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static unsigned long lastUpdate_millis = 0;
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//has enough time passed to update everything?
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if (curTime_millis < lastUpdate_millis) lastUpdate_millis = 0; //handle wrap-around of the clock
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if ((curTime_millis - lastUpdate_millis) > updatePeriod_millis) { //is it time to update the user interface?
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Serial.print("CPU Cur/Peak: ");
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Serial.print(audio_settings.processorUsage());
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Serial.print("%/");
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Serial.print(audio_settings.processorUsageMax());
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Serial.print("%, ");
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Serial.print(" Dyn MEM Float32 Cur/Peak: ");
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Serial.print(AudioMemoryUsage_F32());
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Serial.print("/");
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Serial.print(AudioMemoryUsageMax_F32());
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Serial.print(" MEM Int16 Cur/Peak: ");
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Serial.print(AudioMemoryUsage());
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Serial.print("/");
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Serial.print(AudioMemoryUsageMax());
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Serial.println();
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lastUpdate_millis = curTime_millis; //we will use this value the next time around.
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}
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}
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void printGainSettings(void) {
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Serial.print("Gain (dB): ");
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Serial.print("Vol Knob = "); Serial.print(vol_knob_gain_dB,1);
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//Serial.print(", Input PGA = "); Serial.print(input_gain_dB,1);
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Serial.println();
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}
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void incrementKnobGain(float increment_dB) {
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setVolKnobGain_dB(vol_knob_gain_dB+increment_dB);
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}
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void setVolKnobGain_dB(float gain_dB) {
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vol_knob_gain_dB = gain_dB;
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gain1.setGain_dB(vol_knob_gain_dB);
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printGainSettings();
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}
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int incrementFreqShift(int incr_factor) {
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int cur_shift_bins = freqShift.getShift_bins();
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return freqShift.setShift_bins(cur_shift_bins + incr_factor);
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}
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