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375 lines
15 KiB
C++
375 lines
15 KiB
C++
/*
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* Display A-weighted sound level measured by I2S Microphone
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*
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* (c)2019 Ivan Kostoski
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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/*
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* Sketch samples audio data from I2S microphone, processes the data
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* with digital IIR filters and calculates A or C weighted Equivalent
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* Continuous Sound Level (Leq)
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*
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* I2S is setup to sample data at Fs=48000KHz (fixed value due to
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* design of digital IIR filters). Data is read from I2S queue
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* in 'sample blocks' (default 125ms block, equal to 6000 samples)
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* by 'i2s_reader_task', filtered trough two IIR filters (equalizer
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* and weighting), summed up and pushed into 'samples_queue' as
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* sum of squares of filtered samples. The main task then pulls data
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* from the queue and calculates decibel value relative to microphone
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* reference amplitude, derived from datasheet sensitivity dBFS
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* value, number of bits in I2S data, and the reference value for
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* which the sensitivity is specified (typically 94dB, pure sine
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* wave at 1KHz).
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*
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* Displays line on the small OLED screen with 'short' LAeq(125ms)DB_UNITS
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* response and numeric LAeq(1sec) dB value from the signal RMS.
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*/
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#include <driver/i2s.h>
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#include "sos-iir-filter.h"
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//
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// Configuration
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//
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#define LEQ_PERIOD 1.0 // second(s)
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#define WEIGHTING C_weighting // Also avaliable: 'C_weighting' or 'None' (Z_weighting)
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#define LEQ_UNITS "LAeq" // customize based on above weighting used
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#define DB_UNITS "dBA" // customize based on above weighting used
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// NOTE: Some microphones require at least DC-Blocker filter
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#define MIC_EQUALIZER INMP441 // See below for defined IIR filters or set to 'None' to disable
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#define MIC_OFFSET_DB 3.0103 // Default offset (sine-wave RMS vs. dBFS). Modify this value for linear calibration
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// Customize these values from microphone datasheet
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#define MIC_SENSITIVITY -26 // dBFS value expected at MIC_REF_DB (Sensitivity value from datasheet)
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#define MIC_REF_DB 94.0 // Value at which point sensitivity is specified in datasheet (dB)
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#define MIC_OVERLOAD_DB 116.0 // dB - Acoustic overload point
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#define MIC_NOISE_DB 33 // dB - Noise floor
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#define MIC_BITS 24 // valid number of bits in I2S data
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#define MIC_CONVERT(s) (s >> (SAMPLE_BITS - MIC_BITS))
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#define MIC_TIMING_SHIFT 0 // Set to one to fix MSB timing for some microphones, i.e. SPH0645LM4H-x
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// Calculate reference amplitude value at compile time
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constexpr double MIC_REF_AMPL = pow(10, double(MIC_SENSITIVITY)/20) * ((1<<(MIC_BITS-1))-1);
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//
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// I2S pins - Can be routed to almost any (unused) ESP32 pin.
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// SD can be any pin, inlcuding input only pins (36-39).
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// SCK (i.e. BCLK) and WS (i.e. L/R CLK) must be output capable pins
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//
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// Below ones are just example for my board layout, put here the pins you will use
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//
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#define I2S_WS 2
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#define I2S_SCK 14
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#define I2S_SD 15
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// I2S peripheral to use (0 or 1)
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#define I2S_PORT I2S_NUM_0
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//
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// IIR Filters
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//
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// DC-Blocker filter - removes DC component from I2S data
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// See: https://www.dsprelated.com/freebooks/filters/DC_Blocker.html
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// a1 = -0.9992 should heavily attenuate frequencies below 10Hz
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SOS_IIR_Filter DC_BLOCKER = {
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gain: 1.0,
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sos: {{-1.0, 0.0, +0.9992, 0}}
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};
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//
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// Equalizer IIR filters to flatten microphone frequency response
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// See respective .m file for filter design. Fs = 48Khz.
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//
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// Filters are represented as Second-Order Sections cascade with assumption
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// that b0 and a0 are equal to 1.0 and 'gain' is applied at the last step
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// B and A coefficients were transformed with GNU Octave:
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// [sos, gain] = tf2sos(B, A)
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// See: https://www.dsprelated.com/freebooks/filters/Series_Second_Order_Sections.html
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// NOTE: SOS matrix 'a1' and 'a2' coefficients are negatives of tf2sos output
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//
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// TDK/InvenSense ICS-43434
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// Datasheet: https://www.invensense.com/wp-content/uploads/2016/02/DS-000069-ICS-43434-v1.1.pdf
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// B = [0.477326418836803, -0.486486982406126, -0.336455844522277, 0.234624646917202, 0.111023257388606];
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// A = [1.0, -1.93073383849136326, 0.86519456089576796, 0.06442838283825100, 0.00111249298800616];
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SOS_IIR_Filter ICS43434 = {
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gain: 0.477326418836803,
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sos: { // Second-Order Sections {b1, b2, -a1, -a2}
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{+0.96986791463971267, 0.23515976355743193, -0.06681948004769928, -0.00111521990688128},
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{-1.98905931743624453, 0.98908924206960169, +1.99755331853906037, -0.99755481510122113}
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}
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};
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// TDK/InvenSense ICS-43432
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// Datasheet: https://www.invensense.com/wp-content/uploads/2015/02/ICS-43432-data-sheet-v1.3.pdf
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// B = [-0.45733702338341309 1.12228667105574775 -0.77818278904413563, 0.00968926337978037, 0.10345668405223755]
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// A = [1.0, -3.3420781082912949, 4.4033694320978771, -3.0167072679918010, 1.2265536567647031, -0.2962229189311990, 0.0251085747458112]
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SOS_IIR_Filter ICS43432 = {
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gain: -0.457337023383413,
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sos: { // Second-Order Sections {b1, b2, -a1, -a2}
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{-0.544047931916859, -0.248361759321800, +0.403298891662298, -0.207346186351843},
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{-1.909911869441421, +0.910830292683527, +1.790285722826743, -0.804085812369134},
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{+0.000000000000000, +0.000000000000000, +1.148493493802252, -0.150599527756651}
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}
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};
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// TDK/InvenSense INMP441
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// Datasheet: https://www.invensense.com/wp-content/uploads/2015/02/INMP441.pdf
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// B ~= [1.00198, -1.99085, 0.98892]
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// A ~= [1.0, -1.99518, 0.99518]
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SOS_IIR_Filter INMP441 = {
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gain: 1.00197834654696,
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sos: { // Second-Order Sections {b1, b2, -a1, -a2}
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{-1.986920458344451, +0.986963226946616, +1.995178510504166, -0.995184322194091}
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}
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};
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// Infineon IM69D130 Shield2Go
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// Datasheet: https://www.infineon.com/dgdl/Infineon-IM69D130-DS-v01_00-EN.pdf?fileId=5546d462602a9dc801607a0e46511a2e
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// B ~= [1.001240684967527, -1.996936108836337, 0.995703101823006]
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// A ~= [1.0, -1.997675693595542, 0.997677044195563]
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// With additional DC blocking component
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SOS_IIR_Filter IM69D130 = {
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gain: 1.00124068496753,
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sos: {
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{-1.0, 0.0, +0.9992, 0}, // DC blocker, a1 = -0.9992
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{-1.994461610298131, 0.994469278738208, +1.997675693595542, -0.997677044195563}
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}
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};
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// Knowles SPH0645LM4H-B, rev. B
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// https://cdn-shop.adafruit.com/product-files/3421/i2S+Datasheet.PDF
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// B ~= [1.001234, -1.991352, 0.990149]
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// A ~= [1.0, -1.993853, 0.993863]
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// With additional DC blocking component
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SOS_IIR_Filter SPH0645LM4H_B_RB = {
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gain: 1.00123377961525,
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sos: { // Second-Order Sections {b1, b2, -a1, -a2}
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{-1.0, 0.0, +0.9992, 0}, // DC blocker, a1 = -0.9992
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{-1.988897663539382, +0.988928479008099, +1.993853376183491, -0.993862821429572}
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}
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};
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//
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// Weighting filters
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//
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//
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// A-weighting IIR Filter, Fs = 48KHz
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// (By Dr. Matt L., Source: https://dsp.stackexchange.com/a/36122)
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// B = [0.169994948147430, 0.280415310498794, -1.120574766348363, 0.131562559965936, 0.974153561246036, -0.282740857326553, -0.152810756202003]
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// A = [1.0, -2.12979364760736134, 0.42996125885751674, 1.62132698199721426, -0.96669962900852902, 0.00121015844426781, 0.04400300696788968]
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SOS_IIR_Filter A_weighting = {
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gain: 0.169994948147430,
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sos: { // Second-Order Sections {b1, b2, -a1, -a2}
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{-2.00026996133106, +1.00027056142719, -1.060868438509278, -0.163987445885926},
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{+4.35912384203144, +3.09120265783884, +1.208419926363593, -0.273166998428332},
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{-0.70930303489759, -0.29071868393580, +1.982242159753048, -0.982298594928989}
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}
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};
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//
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// C-weighting IIR Filter, Fs = 48KHz
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// Designed by invfreqz curve-fitting, see respective .m file
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// B = [-0.49164716933714026, 0.14844753846498662, 0.74117815661529129, -0.03281878334039314, -0.29709276192593875, -0.06442545322197900, -0.00364152725482682]
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// A = [1.0, -1.0325358998928318, -0.9524000181023488, 0.8936404694728326 0.2256286147169398 -0.1499917107550188, 0.0156718181681081]
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SOS_IIR_Filter C_weighting = {
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gain: -0.491647169337140,
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sos: {
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{+1.4604385758204708, +0.5275070373815286, +1.9946144559930252, -0.9946217070140883},
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{+0.2376222404939509, +0.0140411206016894, -1.3396585608422749, -0.4421457807694559},
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{-2.0000000000000000, +1.0000000000000000, +0.3775800047420818, -0.0356365756680430}
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}
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};
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//
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// Sampling
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//
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#define SAMPLE_RATE 48000 // Hz, fixed to design of IIR filters
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#define SAMPLE_BITS 32 // bits
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#define SAMPLE_T int32_t
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#define SAMPLES_SHORT (SAMPLE_RATE / 8) // ~125ms
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#define SAMPLES_LEQ (SAMPLE_RATE * LEQ_PERIOD)
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#define DMA_BANK_SIZE (SAMPLES_SHORT / 16)
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#define DMA_BANKS 32
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// Data we push to 'samples_queue'
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struct sum_queue_t {
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// Sum of squares of mic samples, after Equalizer filter
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float sum_sqr_SPL;
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// Sum of squares of weighted mic samples
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float sum_sqr_weighted;
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// Debug only, FreeRTOS ticks we spent processing the I2S data
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uint32_t proc_ticks;
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};
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QueueHandle_t samples_queue;
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// Static buffer for block of samples
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float samples[SAMPLES_SHORT] __attribute__((aligned(4)));
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//
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// I2S Microphone sampling setup
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//
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void mic_i2s_init() {
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// Setup I2S to sample mono channel for SAMPLE_RATE * SAMPLE_BITS
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// NOTE: Recent update to Arduino_esp32 (1.0.2 -> 1.0.3)
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// seems to have swapped ONLY_LEFT and ONLY_RIGHT channels
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const i2s_config_t i2s_config = {
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mode: i2s_mode_t(I2S_MODE_MASTER | I2S_MODE_RX),
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sample_rate: SAMPLE_RATE,
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bits_per_sample: i2s_bits_per_sample_t(SAMPLE_BITS),
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channel_format: I2S_CHANNEL_FMT_ONLY_LEFT,
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communication_format: i2s_comm_format_t(I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB),
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intr_alloc_flags: ESP_INTR_FLAG_LEVEL1,
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dma_buf_count: DMA_BANKS,
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dma_buf_len: DMA_BANK_SIZE,
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use_apll: true,
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tx_desc_auto_clear: false,
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fixed_mclk: 0
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};
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// I2S pin mapping
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const i2s_pin_config_t pin_config = {
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bck_io_num: I2S_SCK,
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ws_io_num: I2S_WS,
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data_out_num: -1, // not used
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data_in_num: I2S_SD
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};
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i2s_driver_install(I2S_PORT, &i2s_config, 0, NULL);
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#if (MIC_TIMING_SHIFT > 0)
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// Undocumented (?!) manipulation of I2S peripheral registers
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// to fix MSB timing issues with some I2S microphones
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REG_SET_BIT(I2S_TIMING_REG(I2S_PORT), BIT(9));
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REG_SET_BIT(I2S_CONF_REG(I2S_PORT), I2S_RX_MSB_SHIFT);
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#endif
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i2s_set_pin(I2S_PORT, &pin_config);
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//FIXME: There is a known issue with esp-idf and sampling rates, see:
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// https://github.com/espressif/esp-idf/issues/2634
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// In the meantime, the below line seems to set sampling rate at ~47999.992Hz
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// fifs_req=24576000, sdm0=149, sdm1=212, sdm2=5, odir=2 -> fifs_reached=24575996
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//NOTE: This seems to be fixed in ESP32 Arduino 1.0.4, esp-idf 3.2
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// Should be safe to remove...
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//#include <soc/rtc.h>
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//rtc_clk_apll_enable(1, 149, 212, 5, 2);
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}
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//
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// I2S Reader Task
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//
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// Rationale for separate task reading I2S is that IIR filter
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// processing cam be scheduled to different core on the ESP32
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// while main task can do something else, like update the
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// display in the example
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//
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// As this is intended to run as separate hihg-priority task,
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// we only do the minimum required work with the I2S data
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// until it is 'compressed' into sum of squares
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//
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// FreeRTOS priority and stack size (in 32-bit words)
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#define I2S_TASK_PRI 4
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#define I2S_TASK_STACK 2048
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//
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void mic_i2s_reader_task(void* parameter) {
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mic_i2s_init();
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// Discard first block, microphone may have startup time (i.e. INMP441 up to 83ms)
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size_t bytes_read = 0;
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i2s_read(I2S_PORT, &samples, SAMPLES_SHORT * sizeof(int32_t), &bytes_read, portMAX_DELAY);
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uint32_t Leq_samples = 0;
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double Leq_sum_sqr = 0;
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double Leq_dB = 0;
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while (true) {
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// Block and wait for microphone values from I2S
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//
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// Data is moved from DMA buffers to our 'samples' buffer by the driver ISR
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// and when there is requested ammount of data, task is unblocked
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//
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// Note: i2s_read does not care it is writing in float[] buffer, it will write
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// integer values to the given address, as received from the hardware peripheral.
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i2s_read(I2S_PORT, &samples, SAMPLES_SHORT * sizeof(SAMPLE_T), &bytes_read, portMAX_DELAY);
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TickType_t start_tick = xTaskGetTickCount();
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// Convert (including shifting) integer microphone values to floats,
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// using the same buffer (assumed sample size is same as size of float),
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// to save a bit of memory
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SAMPLE_T* int_samples = (SAMPLE_T*)&samples;
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for(int i=0; i<SAMPLES_SHORT; i++) samples[i] = MIC_CONVERT(int_samples[i]);
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sum_queue_t q;
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// Apply equalization and calculate Z-weighted sum of squares,
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// writes filtered samples back to the same buffer.
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q.sum_sqr_SPL = MIC_EQUALIZER.filter(samples, samples, SAMPLES_SHORT);
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// Apply weighting and calucate weigthed sum of squares
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q.sum_sqr_weighted = WEIGHTING.filter(samples, samples, SAMPLES_SHORT);
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// Debug only. Ticks we spent filtering and summing block of I2S data
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q.proc_ticks = xTaskGetTickCount() - start_tick;
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// Send the sums to FreeRTOS queue where main task will pick them up
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// and further calcualte decibel values (division, logarithms, etc...)
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double short_RMS = sqrt(double(q.sum_sqr_SPL) / SAMPLES_SHORT);
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double short_SPL_dB = MIC_OFFSET_DB + MIC_REF_DB + 20 * log10(short_RMS / MIC_REF_AMPL);
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// In case of acoustic overload or below noise floor measurement, report infinty Leq value
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if (short_SPL_dB > MIC_OVERLOAD_DB) {
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Leq_sum_sqr = INFINITY;
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} else if (isnan(short_SPL_dB) || (short_SPL_dB < MIC_NOISE_DB)) {
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Leq_sum_sqr = -INFINITY;
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}
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// Accumulate Leq sum
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Leq_sum_sqr += q.sum_sqr_weighted;
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Leq_samples += SAMPLES_SHORT;
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// When we gather enough samples, calculate new Leq value
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if (Leq_samples >= SAMPLE_RATE * LEQ_PERIOD) {
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double Leq_RMS = sqrt(Leq_sum_sqr / Leq_samples);
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Leq_dB = MIC_OFFSET_DB + MIC_REF_DB + 20 * log10(Leq_RMS / MIC_REF_AMPL);
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Leq_sum_sqr = 0;
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Leq_samples = 0;
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// Serial output, customize (or remove) as needed
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//Serial.printf("%.1f\n", Leq_dB);
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// Debug only
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//Serial.printf("%u processing ticks\n", q.proc_ticks);
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xQueueSend(samples_queue, &Leq_dB, portMAX_DELAY);
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}
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vTaskDelay(1);
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}
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}
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void mic_i2s_uninstall(){
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esp_err_t result = i2s_driver_uninstall(I2S_PORT);
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Serial.printf("mic_i2s_uninstall result: %d\r\n", result);
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}
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