main.cpp

00001 /** 10_rtos_mailbox
00002  *
00003  * Simple example to use a Mail object in order to send 
00004  * complex messages from thread1 to thread2.
00005  * Thread1 generates transition between random RGB colors and sends
00006  * messages to Thread2. Thread2 displays the requested color on the
00007  * built in RGB LED.
00008  *
00009  * Data items for messages are stored in a Mail object.
00010  * Thread1 allocates mailbox slots, Thread2 should free up
00011  * these slots after using up data stored in the slot.
00012  */
00013 
00014 #include "mbed.h"
00015 #include "rtos.h"
00016 PwmOut rled(LED_RED);
00017 PwmOut gled(LED_GREEN);
00018 PwmOut bled(LED_BLUE);
00019 
00020 typedef struct {
00021     float red;
00022     float green;
00023     float blue;
00024 } message_t;
00025 
00026 Mail<message_t, 4> mbox;                            //Mailboxes for 4 messages
00027 
00028 
00029 void led_thread(void const *argument)
00030 {
00031     rled.period_ms(20);                             //Set period to 20 ms
00032     rled.write(1.0f);                               //Initialize to 0% duty cycle
00033     gled.period_ms(20);                             //Set period to 20 ms
00034     gled.write(1.0f);                               //Initialize to 0% duty cycle
00035     bled.period_ms(20);                             //Set period to 20 ms
00036     bled.write(1.0f);                               //Initialize to 0% duty cycle
00037     while (true) {
00038         osEvent evt = mbox.get();                   //Wait for a message
00039         if(evt.status == osEventMail) {
00040             message_t *mymessage = (message_t*)evt.value.p;
00041             rled = 1.0f - mymessage->red;
00042             gled = 1.0f - mymessage->green;
00043             bled = 1.0f - mymessage->blue;
00044             mbox.free(mymessage);                  //Free up memory
00045         }
00046     }
00047 }
00048 
00049 float frand(void)
00050 {
00051     int32_t rv = 0x8000 -(rand()&0xFFFF);
00052     return (rv*rv/1073741824.0f);
00053 }
00054 
00055 int main (void)
00056 {
00057     float RGB1[3];
00058     float RGB2[3];
00059     float INC[3];
00060     Thread thread2(led_thread);
00061 //--- Create a random color ---------------------
00062     for (int x=0; x<3; x++) {
00063         RGB1[x] = frand();
00064     }
00065 
00066     while (true) {
00067 //--- Create a new random color -----------------
00068         for (int x=0; x<3; x++) {
00069             RGB2[x] = frand();
00070         }
00071 //--- Determine increments to go from color 1 to color 2 in 25 steps
00072         for (int x=0; x<3; x++) {
00073             INC[x] = (RGB1[x] - RGB2[x]) / 25;
00074         }       
00075 //--- Send color codes to thread2 ---------------
00076         for (int s=0; s<25; s++) {
00077             message_t *message = mbox.alloc();      //Allocate memory
00078             message->red = RGB1[0];
00079             message->green = RGB1[1];
00080             message->blue = RGB1[2];
00081             mbox.put(message);                      //Send data as message
00082             Thread::wait(100);
00083             for (int x=0; x<3; x++) {
00084                 RGB1[x] -= INC[x];                  //Approach to second colour
00085             }
00086         }
00087     }
00088 }