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Cutoff frequency variable LPF, HPF, BPF, and BRF by FIR 160th-order filter.
Dependencies: UIT_ACM1602NI UITDSP_ADDA mbed UIT_AQM1602
main.cpp
- Committer:
- MikamiUitOpen
- Date:
- 2014-12-08
- Revision:
- 0:ca94cfc90365
- Child:
- 1:58271fae2e01
File content as of revision 0:ca94cfc90365:
//------------------------------------------------------------------------------ // Cutoff frequency variable LPF and HPF, // center frequency variable BPF and BRF by FIR 160th-order filter // A0: Signal to be filtered // A2: Value which controls cutoff frequency // // 1: LPF, 3: HPF, 5: BPF, 7: BRF, even: through // 2014/12/07, Copyright (c) 2014 MIKAMI, Naoki //------------------------------------------------------------------------------ #include "mbed.h" #include "ADC_Interrupt.hpp" // for ADC using interrupt #include "DAC_MCP4922.hpp" // for DAC MCP4922 #include "ACM1602NI.hpp" // for LCD display #include "WindowingDesign.hpp" // for design of FIR filter using namespace Mikami; const int FS_ = 16000; // Sampling frequency: 16 kHz ADC_Intr myAdc_(A0, FS_, A1, A2); DAC_MCP4922 myDac_; const int ORDER_ = 160; float hm_[ORDER_/2+1]; float xn_[ORDER_+1]; DigitalIn sw1_(D2, PullDown); DigitalIn sw2_(D3, PullDown); DigitalIn sw4_(D4, PullDown); DigitalIn sw8_(D5, PullDown); WindowingDesign design_(ORDER_, FS_); DigitalOut dOut_(D7); uint16_t a2_ = 0; // Inputted data from A2 pin // Interrupt service routine for ADC void AdcIsr() { dOut_.write(1); xn_[0] = myAdc_.Read(); // Read from A0 myAdc_.Select3rdChannel(); // Select A2 myAdc_.SoftStart(); // ADC start for A2 input //----------------------------------------- // Execute FIR filter float yn = hm_[ORDER_/2]*xn_[ORDER_/2]; for (int k=0; k<ORDER_/2; k++) yn = yn + hm_[k]*(xn_[k] + xn_[ORDER_-k]); for (int k=ORDER_; k>0; k--) xn_[k] = xn_[k-1]; // move input signals //----------------------------------------- if (sw1_ == 0) myDac_.Write(xn_[0]); // Using no filter else myDac_.Write(yn); // Using filter // Read value which controls cutoff frequency a2_ = myAdc_.ReadWait_u16(); myAdc_.Select1stChannel(); // Select A0 myAdc_.ClearPending_EnableIRQ();// Clear pending interrupt // and enable ADC_IRQn dOut_.write(0); } int main() { myDac_.ScfClockTim3(670000); // cutoff frequency: 6.7 kHz Acm1602Ni lcd; // objetc for display using LCD // Clear buffer in FIR filter for (int n=0; n<=ORDER_; n++) xn_[n] = 0; myAdc_.SetIntrVec(AdcIsr); // Assign ISR for ADC interrupt float fc1 = 0; while (true) { // fc: cutoff or center frequency, 200 -- 2000 Hz float fc = 1800.0f*(a2_/4095.6f) + 200.0f; int sw = (sw8_ << 3) | (sw4_ << 2) | (sw2_ << 1) | sw1_; if (sw1_ == 0) { printf("Through\r\n"); lcd.ClearLine(1); lcd.WriteStringXY("Through ", 0, 0); wait(0.2f); lcd.ClearLine(0); fc1 = 0; } else { if (fabs(fc - fc1) > 10.0f) { printf("fc = %4d\r\n", int(fc+0.5f)); char str[18]; sprintf(str, "fc = %4d Hz", int(fc+0.5f)); lcd.WriteStringXY(str, 0, 1); if (sw == 1) { printf("LPF\r\n"); lcd.WriteStringXY("LPF", 0, 0); design_.Design(ORDER_, WindowingDesign::LPF, fc, 0, hm_); } if (sw == 3) { printf("HPF\r\n"); lcd.WriteStringXY("HPF", 0, 0); design_.Design(ORDER_, WindowingDesign::HPF, fc, 0, hm_); } if (sw == 5) { printf("BPF\r\n"); lcd.WriteStringXY("BPF", 0, 0); design_.Design(ORDER_, WindowingDesign::BPF, fc-100, fc+100, hm_); } if (sw == 7) { printf("BRF\r\n"); lcd.WriteStringXY("BRF", 0, 0); design_.Design(ORDER_, WindowingDesign::BRF, fc-100, fc+100, hm_); } fc1 = fc; } } wait(0.1f); } }