main.cpp

00001 #include "mbed.h"
00002 
00003 //Function prototype
00004 void doSample1Hz();
00005 
00006 //Global objects
00007 Serial pc(USBTX, USBRX);
00008 AnalogIn POT_ADC_In(A0);
00009 DigitalOut led(LED1);
00010 
00011 #define N 16 
00012 
00013 //Shared variables
00014 volatile static unsigned short sample16 = 0;
00015 
00016 unsigned int sum = 0;
00017 unsigned int count = 0;
00018 
00019 //The ticker, used to sample data at a fixed rate
00020 Ticker t;
00021 
00022 //Main function
00023 int main()
00024 {
00025     //Set baud rate to 115200
00026     pc.baud(115200);
00027 
00028     //Set up the ticker - 100Hz
00029     t.attach(doSample1Hz, 0.01);
00030 
00031     while(1) {
00032 
00033         //Sleep
00034         sleep();
00035         
00036         //Add new sample to the sum
00037         sum += sample16;
00038         
00039         //Increment the count
00040         count++;
00041         
00042         //Enough to calculate the average?
00043         if (count == N) {
00044             //Divide sum by 16
00045             unsigned short mean = (sum >> 4);   
00046             
00047             //Display
00048             pc.printf("Mean = %hu\n", mean);
00049             
00050             //Reset sum and count
00051             count = sum = 0;
00052         }
00053  
00054     } //end while(1)
00055 } //end main
00056 
00057 //ISR for the ticker - simply there to perform sampling
00058 void doSample1Hz()
00059 {
00060     //Toggle on board led
00061     led = !led;
00062 
00063     //READ ADC as an unsigned integer.
00064     //Shift right 4 bits (this is a 12bit ADC) & store in static global variable
00065     sample16 = POT_ADC_In.read_u16() >> 4;
00066 }
00067 
00068