main.cpp

00001 /*
00002     Project: Nightlight2
00003     File: main.cpp
00004     
00005     See Word document.
00006     
00007     Written by: Dr. C. S. Tritt
00008     Created: 3/26/17 (v. 1.0)
00009     
00010 */
00011 #include "mbed.h"
00012 
00013 const int HIGH = 1; // Inclusion is optional, but makes code more readable.
00014 const int LOW = 0; // Inclusion is optional, but makes code more readable.
00015 
00016 const float br_min = 0.070; // Read from serial stream and enter.
00017 const float br_max = 0.430; // Read from serial stream and enter.
00018 const float k_1 = 0.7; // These values work well...
00019 const float k_2 = 0.5;
00020 const float k_3 = 0.3;
00021 const float all_off = br_min + k_1*(br_max - br_min); // Thresholds... All off.
00022 const float blu_grn = br_min + k_2*(br_max - br_min); // Blue-green fade.
00023 const float grn_red = br_min + k_3*(br_max - br_min); // Green-red fade.
00024  
00025 AnalogIn photocell(A1); // Create object for photocell.
00026 PwmOut red(D9), grn(D10), blu(D11); // Create objects for LED connected pins.
00027 
00028 int main() {
00029     float brightness; // 0 to 1 max. range. Larger indicates brighter light.
00030     
00031     printf("\nSmart nightlight example\n"); // ID software.
00032     
00033     while(true) {
00034         brightness = photocell; // Read light level (0 to 1).
00035         printf("Value = %f\n", brightness); // Send as text via serial port.
00036         if (brightness > all_off) { // Bright light. All LEDs off.
00037           red = LOW;
00038           grn = LOW;
00039           blu = LOW;
00040         }
00041         else if (brightness > blu_grn) { // Blue to green fade.
00042           red = LOW;
00043           grn = (all_off - brightness)/(all_off - blu_grn);
00044           blu = 1.0f - grn;
00045         }
00046         else if (brightness > grn_red) { // Green to red fade.
00047           red = (blu_grn - brightness)/(blu_grn - grn_red);
00048           grn = 1.0f - red;
00049           blu = LOW;
00050         }
00051         else { // Red on full intensity.
00052           red = HIGH;
00053           grn = LOW;
00054           blu = LOW;            
00055         }
00056         wait(0.1); // Delay 100 ms
00057     }
00058 }