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287 lines
9.4 KiB
287 lines
9.4 KiB
/*
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* radioBFSKmodulator_F32.h
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*
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* BFSK Modulator including control line low-pass filtering
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* By Bob Larkin W7PUA 17 March 2022
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*
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* Thanks to PJRC and Pau Stoffregen for the Teensy processor, Teensyduino
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* and Teensy Audio. Thanks to Chip Audette for the F32 extension
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* work. Alll of that makes this possible. Bob
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*
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* Copyright (c) 2020 Bob Larkin
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice, development funding notice, and this permission
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* notice shall be included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*
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Notes:
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Modem type: V.23 forward channel
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Data rates: 600-/1200-bps half duplex
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Symbol rate: 600/1200 baud (1 bit/symbol)
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Sample rate: 9.6 kHz
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Mean frequency: Mode 1 (600 bps) 1500 Hz 1 = 1300 Hz 0 = 1700 Hz
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Mode 2 (1200 bps) 1700 Hz 1 = 1300 Hz 0 = 2100 Hz
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Frequency deviation: Mode 1 ±200 Hz
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Mode 2 ±400 Hz
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Tx power spectrum: As per V.2 not exceeding -13 dBm
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Receiver: FSK receiver structure based on quadrature baseband time-delay
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multiply
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Rx performance: 600 bps Flat channel: 11-dB SNR for 1e-5 block error rate
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(1000 bits/block)
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1200 bps Flat channel: 16.5-dB SNR for 1e-5 block error rate
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(1000 bits/block)
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Modem type: V.23 backward channel
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Data rate: 75-bps half duplex
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Symbol rate: 75 baud (1 bit/symbol)
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Sample rate: 9.6 kHz
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Mean frequency: 420 Hz 1 = 390 Hz 0 = 450 Hz
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Frequency deviation: ±30 Hz
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*/
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/*
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* Binary Frequency Shift Keying modulator
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* Very general as this can be used to send 1 to 32 bit words at any
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* rate and frequencies only constrained by fs/2 limitations. The bit
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* meanings are just 0 or 1. So, start bits, parity and ending bits
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* are all just part of the transmitted data. For 8N1 select
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* 10 bits here and construct a 0 start bit and a 1 ending bit.
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* For instance: If ch8 is an 8-bit character, we transmit
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* 0X200 | (ch8 << 1).
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*
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* After a bit is determined, there is an optional low-pass FIR filter to limit
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* the transmit bandwidth. This produces a non-binary frequency that
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* is set by a phase increment.
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*
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* The update() uses about 13 microseconds for 128 points with no LPF
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* on the control signal. The LPF adds roughly 3 icroseconds per
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* FIR coefficient being used.
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*
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* 2 April 2023 -Corrected to handle outputs from full buffer. RSL
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* Added int16_t getBufferSpace(). RSL
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*/
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/* Here is an Octave/Matlab .m file to design the Gaussian LP FIR filter
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% FIR Gaussian Pulse-Shaping Filter Design - Based roughly on
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% https://www.mathworks.com/help/signal/ug/fir-gaussian-pulse-shaping-filter-design.html
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%
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symbolRate = 1200.0
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Ts = 1.0/symbolRate; % Symbol time (sec)
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span = 4; % Filter span in symbols
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sampleRate = 48000.0
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overSampleFactor = sampleRate/symbolRate % For printing info
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% nFIR is constrained. Check smallest coefficient and if too big, adjust span
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nFIR = span*sampleRate/symbolRate;
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if rem(nFIR, 2) == 0
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nFIR = nFIR + 1;
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endif
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nFIR
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%
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% Important BT parameter:
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BT = 0.4
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a = Ts*sqrt(0.5*log(2))/BT;
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B = sqrt(log(2)/2)./(a);
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B3dB = B % For printing info
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t = linspace(-span*Ts/2, span*Ts/2, nFIR)';
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cf32f = zeros(nFIR); % FIR coefficients
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cf32f = sqrt(pi)/a*exp(-(pi*t/a).^2);
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cf32f = (cf32f./sum(cf32f)) % Column vector, normalized for DC gain of 1
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*/
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/* Gaussian FSK LPF Filter A Sample filter per AIS radios.
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* Paste from here into INO program, or design a different LPF.
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* This filter corresponds to:
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* symbolRate = 9600
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* sampleRate = 48000
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* overSampleFactor = 5
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* nFIR = 21
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* BT = 0.40000
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* B3dB = 3840.0
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* Atten at 9600 Hz = 18.8 dB
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float32_t gaussFIR9600_48K[21] = {
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0.0000000029f,
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0.0000000934f,
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0.0000020700f,
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0.0000318610f,
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0.0003406053f,
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0.0025289299f,
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0.0130411453f,
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0.0467076746f,
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0.1161861408f,
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0.2007307811f,
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0.2408613913f,
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0.2007307811f,
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0.1161861408f,
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0.0467076746f,
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0.0130411453f,
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0.0025289299f,
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0.0003406053f,
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0.0000318610f,
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0.0000020700f,
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0.0000000934f,
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0.0000000029f}; */
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#ifndef _radioBFSKmodulator_f32_h
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#define _radioBFSKmodulator_f32_h
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#include "AudioStream_F32.h"
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#include "arm_math.h"
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#include "mathDSP_F32.h"
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#include <math.h>
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class RadioBFSKModulator_F32 : public AudioStream_F32 {
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//GUI: inputs:0, outputs:1 //this line used for automatic generation of GUI node
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//GUI: shortName: BFSKmodulator
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public:
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// Option of AudioSettings_F32 change to block size or sample rate:
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RadioBFSKModulator_F32(void) : AudioStream_F32(0, NULL) {
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// Defaults
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}
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RadioBFSKModulator_F32(const AudioSettings_F32 &settings) : AudioStream_F32(0, NULL) {
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setSampleRate_Hz(settings.sample_rate_Hz);
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block_size = settings.audio_block_samples;
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}
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#define DATA_BUFFER_EMPTY 0
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#define DATA_BUFFER_PART 1
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#define DATA_BUFFER_FULL 2
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// As viewed from the INO, does the bufffer have space?
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bool bufferHasSpace(void) {
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checkBuffer();
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if(stateBuffer == DATA_BUFFER_FULL)
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return false;
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else
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return true;
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}
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int16_t getBufferSpace(void) {
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return 64-checkBuffer();
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}
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// As viewed from the INO, put a data word into the buffer to send.
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// Returns true if successful.
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bool sendData(uint32_t data) {
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checkBuffer();
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if(stateBuffer == DATA_BUFFER_FULL)
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return false;
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else
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{
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indexIn++;
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dataBuffer[indexIn & indexMask] = data;
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checkBuffer();
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return true;
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}
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}
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void bufferClear(void) {
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indexIn = 0LL;
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indexOut = 0LL;
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}
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// Sets all parameters for BFSK modulation
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// Returns number of audio samplesPerDataBit
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uint32_t setBFSK(float32_t _bitRate, uint16_t _numBits, float32_t _f0, float32_t _f1) {
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bitRate = _bitRate;
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numBits = _numBits;
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// Transmission rates are quantized by sample rate. On this transmit side,
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// it seems best to error on the side of sending too fast. Thus ceilf()
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samplesPerDataBit = (uint16_t)(ceilf((sample_rate_Hz/bitRate) - 0.0000001));
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freq[0] = _f0;
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freq[1] = _f1;
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phaseIncrement[0] = kp*freq[0];
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phaseIncrement[1] = kp*freq[1];
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deltaPhase = kp*(freq[1] - freq[0]);
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return samplesPerDataBit;
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}
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// The amplitude, a, is the peak, as in zero-to-peak. This produces outputs
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// ranging from -a to +a.
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void amplitude(float32_t a) {
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if (a < 0.0f) a = 0.0f;
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magnitude = a;
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}
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// Low pass filter on frequency control line. Set to NULL to omitfilter.
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void setLPF(float32_t* _FIRdata, float32_t* _FIRcoeff, uint16_t _numCoeffs) {
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FIRdata = _FIRdata;
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if(_FIRcoeff == NULL || _numCoeffs == 0)
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{
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FIRcoeff = NULL;
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numCoeffs = 0;
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return;
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}
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FIRcoeff = _FIRcoeff;
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numCoeffs = _numCoeffs;
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if(numCoeffs != 0)
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indexFIRMask = (uint64_t)(powf(2, (ceilf(logf(numCoeffs)/logf(2.0f)))) - 1.000001f);
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}
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void setSampleRate_Hz(const float &fs_Hz) {
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sample_rate_Hz = fs_Hz;
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kp = 512.0f/sample_rate_Hz;
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phaseIncrement[0] = kp*freq[0];
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phaseIncrement[1] = kp*freq[1];
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deltaPhase = kp*(freq[1] - freq[0]);
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samplesPerDataBit = (uint32_t)(0.5 + sample_rate_Hz/bitRate);
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}
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int16_t checkBuffer(void);
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virtual void update(void);
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#define DATA_BUFFER_EMPTY 0
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#define DATA_BUFFER_PART 1
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#define DATA_BUFFER_FULL 2
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private:
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float32_t sample_rate_Hz = AUDIO_SAMPLE_RATE_EXACT;
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uint16_t block_size = 128;
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float32_t freq[2] = {1300.000f, 2100.000f};
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float32_t kp = 512.0f/sample_rate_Hz;
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float32_t phaseIncrement[2] = {kp*freq[0], kp*freq[1]};
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float32_t deltaPhase = kp*(freq[1] - freq[0]);
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float32_t bitRate = 1200.0f;
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float32_t currentPhase = 0.0f;
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float32_t magnitude = 1.0f;
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uint32_t currentWord = 0UL;
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uint16_t numBits = 10;
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uint16_t bitSendCount = 0;
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uint32_t dataBuffer[64]; // Make 64 a define??
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// By using a 64-bit index we never need to wrap around.
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// We create a circular 64-word buffer with the mask.
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int64_t indexIn = 0ULL; // Next word to be entered to buffer
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int64_t indexOut = 0ULL; // Next word to be sent
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int64_t indexMask = 0X003F; // Goes with 64
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uint16_t stateBuffer = DATA_BUFFER_EMPTY;
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uint16_t vc = 0;
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uint32_t samplePerBitCount = 0;
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// The next for 1200 bit/sec and 44100 sample rate is 37 samples,
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// or actually 1192 bits/sec.
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// For 9600 bit/sec and 96000 sample rate is 10 samples.
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uint32_t samplesPerDataBit = (uint32_t)(0.5 + sample_rate_Hz/bitRate);
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float32_t* FIRdata = NULL;
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float32_t* FIRcoeff = NULL;
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uint16_t numCoeffs = 0;
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uint64_t indexFIRlatest = 0; // Next word to be entered to buffer
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uint64_t indexFIRMask = 0X001F; // Goes with 32
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};
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#endif
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