main.cpp

00001 #include "mbed.h"
00002 #include "main.h"
00003 
00004 #include "BP_4KHz_Fc_35KHz_Fs_5N.h"
00005 
00006 //MBED Class Instances follows
00007 DigitalOut SampLED(LED1);              //Digital Output  (GREEN LED is PB_3, D13 You can use an Oscilloscope on This pin to confirm sample rate)
00008 
00009 AnalogIn  Ain(PA_1);                    //Analog Input (Signal Input 0 to +3 Volts)
00010 AnalogOut Aout(PA_4);                   //Analog Output (Signal Input 0 to +3 Volts)
00011 
00012 Ticker sample_timer;
00013 
00014 //Ticker routine PROTOTYPE to service samples from Analogue IP and port to Analogue Output
00015 void sampler(void);
00016 
00017 int main() {
00018    
00019     float sample_rate=(1.0/Fs)*1000000.0; //Calculate the number of uS required for a Frequency Sampling Rate
00020                                           //Fs held in init.h
00021     sample_timer.attach_us(&sampler,(int)sample_rate);
00022                                           //Ticker Instance serviced by routine at a repeat rate in microseconds
00023   
00024     while(1) {
00025           sleep();
00026     }
00027 }
00028 
00029 //Ticker routine to service samples from Analogue IP and port to Analogue Output
00030 void sampler(void)
00031 {
00032     SampLED = ON;       //LED Indicates start of sampling
00033 
00034     xn=Ain;               //Input ADC. N.B. ADC in MBED is 0.0 to 1.0 float!!!!!!
00035 
00036     centreTap = xn*b0 + xnm1*b1 + xnm2*b2 + xnm3*b3 + xnm4*b4;  //IIR Filter
00037     yn = centreTap*a0 - a1*ynm1 - a2*ynm2  - a3*ynm3 - a4*ynm4; //Result in yn
00038   
00039     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
00040   
00041     //THESE NEED TO BE LOADED IN THIS ORDER OTHERWISE ALL xnm VALUES WILL BECOME THE SAME AS xn
00042     xnm4 = xnm3;
00043     xnm3 = xnm2;
00044     xnm2 = xnm1;
00045     xnm1 = xn;  
00046     
00047     //THESE NEED TO BE LOADED IN THIS ORDER OTHERWISE ALL ynm VALUES WILL BECOME THE SAME AS yn
00048     ynm4 = ynm3;
00049     ynm3 = ynm2;
00050     ynm2 = ynm1;
00051     ynm1 = yn;
00052 
00053     SampLED = OFF;      //LED Indicates end of sampling
00054 }
00055