main.cpp

00001 /*
00002  * The program try to test the phenomenon as mentioned in
00003  * http://mbed.org/users/chris/notebook/Getting-best-ADC-performance/
00004  *
00005  *  a) Unused ADC pins are either tied to ground, or declared as DigitalOut
00006  *  b) Quality of signal source, including low noise design techniques such 
00007  *     as filtering. 
00008  *  c) Reduce debugging communication via USB
00009  */
00010  
00011 #include "mbed.h"
00012 
00013 #define   SSIZE 100
00014 
00015 AnalogIn  ain(p20);
00016 BusOut    unused(p15,p16,p17,p18,p19);  // Make unused analog pin to DigitalOut
00017 
00018 float     value[SSIZE];
00019 float     max;
00020 float     min;
00021 double    itg;
00022 
00023 void printNow()
00024 {
00025   time_t    s;
00026   char      buffer[20];
00027 
00028   s = time(NULL);
00029   strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", localtime(&s));
00030   printf("%s\n", buffer);
00031 }
00032 
00033 void printSecNow()
00034 {
00035   time_t    s;
00036   s = time(NULL);
00037   printf("%d\n", s);
00038 }
00039 
00040 int main() 
00041 {
00042   set_time(1323180910);
00043 
00044   while (1)
00045   {
00046     //printNow();
00047     printf("\n-----------------\n");
00048     printSecNow();
00049     max = itg = 0.0;
00050     min = 3.3;
00051     // Sample before printing to avoid debug communucation
00052     for (int i=0; i<SSIZE; i++)
00053     {
00054       value[i] = ain;
00055       if (value[i] > max) max = value[i];
00056       if (value[i] < min) min = value[i];
00057       itg += value[i];
00058     }
00059     printSecNow();
00060     
00061     // Now print out
00062     for (int i=0; i<SSIZE; i++)
00063     {
00064       printf("%0.3f ", value[i]*3.3);  
00065     }
00066     printf("\n");
00067     printf("max=%0.3f, min=%0.3f, avg=%0.3f\n", 
00068            max*3.3, min*3.3, 3.3*itg/SSIZE);
00069     wait(10);
00070   }
00071 }