main.cpp

00001 /** 05_comparator_demo
00002  *  Simple program to demonstrate the basic functions
00003  *  of the analog comparator of the FRDM-KL25Z board.
00004  *
00005  *  Used library:
00006  *   - ComparatorIn //https://developer.mbed.org/users/frankvnk/code/ComparatorIn/
00007  *     written by Frank Vannieuwkerke
00008  *
00009  *  Hardware requirements:
00010  *   - FRDM-KL25 board
00011  *   - CdS photoresistor pulled up by 10 k
00012  *   - Connecect the midpoint of the divider to PTE29
00013  *
00014  *            10k          CdS photoresistor
00015  *   +3.3V --/\/\/\---+---/\/\/\---- GND
00016  *                    |
00017  *                  PTE29
00018  *
00019  */
00020 
00021 #include "mbed.h"
00022 #include "ComparatorIn.h"
00023  
00024 DigitalOut blinker (LED_BLUE);      // blinking LED
00025 DigitalOut cmpled (LED_GREEN);      // signing comparator status
00026 AnalogIn cmp_lvl (PTE29);           // ADC input to check comparator input
00027 ComparatorIn compi(PTE29, PTE30);   // in+ = PTE29, in- = 12-bit DAC 
00028  
00029 // Comparator interrupt callback functions
00030 void cmp_rise_ISR(void)
00031 {
00032     cmpled = 0;                     // LED ON at rising edge
00033 }
00034  
00035 void cmp_fall_ISR(void)
00036 {
00037     cmpled = 1;                     // LED OFF at falling edge
00038 }
00039  
00040  
00041  
00042 int main()
00043 {
00044     cmpled = 1;                     // LED OFF at the beginning
00045  
00046     compi.rising(&cmp_rise_ISR);    // Set pointer to rising interrupt function
00047     compi.falling(&cmp_fall_ISR);   // Set pointer to falling interrupt function
00048     compi.treshold(0.3);            // Set comparator threshold to 1V = 0.3 * 3.3V
00049  
00050     while(1)
00051     {
00052         printf("Light sensor : %7.5f Volt\n",cmp_lvl*3.3);
00053         blinker = 1;                // binking LED OFF
00054         wait(2);                    // wait for 2 sec
00055         blinker = 0;                // blinking LED ON
00056         wait(0.2);
00057         if (compi.status() == 0x01) // poll comparator status
00058         {
00059             printf("*** Treshold reached : %7.5f\n",cmp_lvl*3.3);
00060         }
00061     }
00062 }
00063  
00064