Martin Simpson
/
ELEC347_STM303K8_IIR
IIR Sample Code
main.cpp
- Committer:
- martinsimpson
- Date:
- 2017-10-13
- Revision:
- 0:cf938939cb77
File content as of revision 0:cf938939cb77:
#include "mbed.h" #include "main.h" #include "BP_4KHz_Fc_35KHz_Fs_5N.h" //MBED Class Instances follows DigitalOut SampLED(LED1); //Digital Output (GREEN LED is PB_3, D13 You can use an Oscilloscope on This pin to confirm sample rate) AnalogIn Ain(PA_1); //Analog Input (Signal Input 0 to +3 Volts) AnalogOut Aout(PA_4); //Analog Output (Signal Input 0 to +3 Volts) Ticker sample_timer; //Ticker routine PROTOTYPE to service samples from Analogue IP and port to Analogue Output void sampler(void); int main() { float sample_rate=(1.0/Fs)*1000000.0; //Calculate the number of uS required for a Frequency Sampling Rate //Fs held in init.h sample_timer.attach_us(&sampler,(int)sample_rate); //Ticker Instance serviced by routine at a repeat rate in microseconds while(1) { sleep(); } } //Ticker routine to service samples from Analogue IP and port to Analogue Output void sampler(void) { SampLED = ON; //LED Indicates start of sampling xn=Ain; //Input ADC. N.B. ADC in MBED is 0.0 to 1.0 float!!!!!! centreTap = xn*b0 + xnm1*b1 + xnm2*b2 + xnm3*b3 + xnm4*b4; //IIR Filter yn = centreTap*a0 - a1*ynm1 - a2*ynm2 - a3*ynm3 - a4*ynm4; //Result in yn Aout=yn+0.5f; //Output resultant to DAC. Again MBED uses 0.0 to 1.0 float!!!!!! and Offset to give 0 to 3V3 range //THESE NEED TO BE LOADED IN THIS ORDER OTHERWISE ALL xnm VALUES WILL BECOME THE SAME AS xn xnm4 = xnm3; xnm3 = xnm2; xnm2 = xnm1; xnm1 = xn; //THESE NEED TO BE LOADED IN THIS ORDER OTHERWISE ALL ynm VALUES WILL BECOME THE SAME AS yn ynm4 = ynm3; ynm3 = ynm2; ynm2 = ynm1; ynm1 = yn; SampLED = OFF; //LED Indicates end of sampling }