Revision 1:131a940a952c, committed 2013-10-17

Comitter:

chenjian221

Date:

Thu Oct 17 00:05:21 2013 +0000

Parent:

0:07ac8eb1700b

Commit message:

add comments, change enable from DigitalOut to PwmOut

Changed in this revision

--- a/main.cpp	Wed Oct 16 04:32:34 2013 +0000
+++ b/main.cpp	Thu Oct 17 00:05:21 2013 +0000
@@ -1,14 +1,20 @@
-#include "mbed.h"
 
+/* This program demonstrates the ability of a color sensor made by
+ * Atlas Scientific through a shiftbrite LED chasing game.
+ * Bi Ge bge6@gatech.edu
+ */
+
+#include "mbed.h"
 DigitalOut latch(p15);
-DigitalOut enable(p16);
+PwmOut enable(p23); // use PWM instead of DigitalOut to dim the LED
 Serial color_sensor(p9, p10);
 
 DigitalOut out_latch(p22);
-DigitalOut out_enable(p21);
-SPI spi(p11, p12, p13);
-SPI out_spi(p5, p6, p7);
+PwmOut out_enable(p21);
+SPI spi(p11, p12, p13); // the random shiftbrite
+SPI out_spi(p5, p6, p7); // this shiftbrite is attached to the color sensor
 
+// http://mbed.org/users/4180_1/notebook/shiftbrite1/
 void RGB_LED(int red, int green, int blue)
 {
     unsigned int low_color=0;
@@ -20,7 +26,9 @@
     latch=1;
     latch=0;
 }
-
+/* This function is exactly the same as the one above, the only
+ * difference is now it outputs value to the second shiftbrite
+ */
 void out_RGB_LED(int red, int green, int blue)
 {
     unsigned int low_color=0;
@@ -34,8 +42,9 @@
 }
 void split_RGB(char* color_str)
 {
-    char *save_ptr;
-    char *p = strtok_r(color_str, ",", &save_ptr);
+    char *save_ptr; // this ptr is used by strtok_r to save
+    // the current parsing state
+    char *p = strtok_r(color_str, ",", &save_ptr); // parse with ","
     int red = strtol(p, NULL, 10);
     p = strtok_r(NULL, ",", &save_ptr);
     int green = strtol(p, NULL, 10);
@@ -47,12 +56,17 @@
 void get_color()
 {
     if(color_sensor.readable()) {
-        printf("get into the function\n");
         char str[11];
         int i = 0;
         char c;
+        /*
+         * The color sensor sends its output in form
+         * "rrr,ggg,bbb\r" in char. It can also output the
+         * light intensity. See product document.
+         */
+
         while(c=color_sensor.getc()) {
-            //printf("read: %c\n", c);
+            // wait for the carriage return
             if(c!='\r') {
                 str[i] = c;
                 i++;
@@ -60,10 +74,6 @@
                 break;
             }
         }
-        //color_sensor.scanf("%s", &str);
-        printf("another read: ");
-        printf("%s\n", str);
-        printf("i=%d\n", i);
         split_RGB(str);
     }
     return;
@@ -77,9 +87,9 @@
     spi.frequency(500000);
     out_spi.format(16,0);
     out_spi.frequency(500000);
-    enable=0;
+    enable=0.5; // set PWM to half, full on is too bright
     latch=0;
-    out_enable=0;
+    out_enable=0.5;
     out_latch=0;
     color_sensor.baud(38400);
     wait(2);
@@ -88,10 +98,12 @@
         green = rand() % 50;
         blue = rand() % 50;
         RGB_LED( red, green, blue);
-        
+        /* IMPORTANT: The color sensor can only take a measurement every 620ms
+         * Have to wait for the instruction to complete.
+         */
         get_color();
         wait(1);
     }
- 
+
 
 }