Diff: main.cpp

Revision:

4:587825079f11

Parent:

3:439f58e558e5

Child:

5:307135bd050f

diff -r 439f58e558e5 -r 587825079f11 main.cpp
--- a/main.cpp	Mon Oct 09 15:51:08 2017 +0000
+++ b/main.cpp	Wed Oct 11 01:59:34 2017 +0000
@@ -1,51 +1,81 @@
 /*
-    Project: TimeoutEX
+    Project: TrafficEx
     File: main.cpp
     
-    Button interrupt sets global config flag. Timeout clears it. Them main 
-    program flashes red or green LED based on config status.
+    Control a hypothetical traffic light using Timeouts. Display a Violation 
+    message if light is run (using polling in main).
+    
+    Car active high input (D6) is created by placing the photocell on the low 
+    side of a voltage divider created using a series of 1 kOhm resistors (the 
+    number depends on ambient conditions). Three worked well for me.
+    
+    The red, yellow and green LEDs are connected to pins D2, D3 and D4, 
+    respectively through 330 Ohm resistors. They are active high.
     
     Created by Dr. C. S. Tritt
-    Last revised: 10/9/17 (v. 1.1)
+    Last revised: 10/10/17 (v. 1.0)
 */
 #include "mbed.h"
 
-void buttonISR(); // Button ISR declaration.
-void configOff(); // Configuration mode off declaration.
+const float grnTime = 3.0f; // Green duration.
+const float ylwTime = 2.0f; // Yellow duration.
+const float redTime = 4.0f; // Red duration.
+
+// These functions change to the indicated color and schedule the next change.
+void grnChange();
+void ylwChange();
+void redChange();
  
-InterruptIn myButton(USER_BUTTON); // Button is normally high. Goes low w/press.
-Timeout configTime; // TimeOut constructor takes no arguments.
+Timeout changeLight; // Reuse for all colors.
 
-DigitalOut redLED(D2); // Red and green LED junctions.
-DigitalOut grnLED(D3);
+// Red, yellow and green LEDs.
+DigitalOut redLight(D2);
+DigitalOut ylwLight(D3);
+DigitalOut grnLight(D4);
 
-bool config = false; // Configuration mode flag.
+// Analog signal used as digital input. Threshold is about 1.6 V.
+DigitalIn car(D6);
 
 int main() {
-    redLED = 0; // Turn red & green off at start.
-    grnLED = 0; 
+    
+    redLight = 1; // Start with red on. Seems safest.
+    grnLight = 0;
+    ylwLight = 0;
     
-    myButton.fall(&buttonISR); // Register ISR routine.
- 
+    redChange(); // Call redChange to start cycling.
+    
+    // redChange will return here almost immediately (after scheduling 
+    // grnChange).
+    
     while(true) { // Main loop.
-        if (config) {
-            redLED = !redLED; // Toggle red junction.
+        // Display RYG status, stay on line. Okay to use printf in main.
+        printf("RYG: %d %d %d. ", (int) redLight, (int) ylwLight, 
+            (int) grnLight);
+        // Display car status, stay on line.    
+        printf("Car: %d.", (int) car);
+        if ((int) car && (int) redLight) {
+            printf(" Violation!\n"); // Note violation.
         } else {
-            grnLED = !grnLED; // Toggle green junction.
-        }
+            printf("\n"); // Just advance a line.
+        }     
         wait(0.5); // Pause half a second.
     }
 }
 
-void buttonISR() { // Sets config status when button falls.
-    config = true; // Set config status.
-    grnLED = 0; // Force green junction off.
-    redLED = 1; // Turn red junction on.
-    configTime.attach(&configOff, 5.0f); // Register callback. 5 sec. delay.
+void grnChange(){
+    redLight = 0; // Turn off red.
+    grnLight = 1; // Turn on green. 
+    changeLight.attach(&ylwChange, grnTime); // Schedule change to yellow. 
 }
 
-void configOff() { // Clears config flag after timeout.
-    config = false; // Clear config flag.
-    redLED = 0; // Force red junction off.
-    grnLED = 1; // Turn green junction on.
+void ylwChange(){
+    grnLight = 0; // Turn off grn.
+    ylwLight = 1; // Turn on yellow. 
+    changeLight.attach(&redChange, ylwTime); // Schedule change to red.    
+}
+
+void redChange(){
+    ylwLight = 0; // Turn off yellow.
+    redLight = 1; // Turn on red. 
+    changeLight.attach(&grnChange, redTime); // Schedule change to green.
 }
\ No newline at end of file