István Cserny / Mbed 2 deprecated Lab08_rtos_mailbox

Simple example to use a Mail object in order to send complex messages from thread1 to thread2. Thread1 generates transition between random RGB colors and sends messages to Thread2. Thread2 displays the requested color on an RGB LED. Data items for messages are stored in a Mail object. Thread1 allocates mailbox slots, Thread2 should free up these slots after using up data stored in the slot.

Dependencies:   mbed mbed-rtos

main.cpp

Committer:
cspista
Date:
2022-03-17
Revision:
0:9f2b4b5956c0

File content as of revision 0:9f2b4b5956c0:

#include "mbed.h"
#include "rtos.h"
PwmOut rled(D3);
PwmOut gled(D5);
PwmOut bled(D6);
DigitalOut led_common(D4);

typedef struct {
    float red;
    float green;
    float blue;
} message_t;

Mail <message_t,4> mbox;                            //Mailbox for 4 messages

void led_thread(void const *argument) {
    rled.period_ms(20);                             //Set period to 20 ms
    rled.write(1.0f);                               //Initialize to 0% duty cycle
    gled.period_ms(20);                             //Set period to 20 ms
    gled.write(1.0f);                               //Initialize to 0% duty cycle
    bled.period_ms(20);                             //Set period to 20 ms
    bled.write(1.0f);                               //Initialize to 0% duty cycle
    while (true) {
        osEvent evt = mbox.get();                   //Wait for a message
        if(evt.status == osEventMail) {
            message_t *mymessage = (message_t*)evt.value.p;
            rled = 1.0f - mymessage->red;
            gled = 1.0f - mymessage->green;
            bled = 1.0f - mymessage->blue;
            mbox.free(mymessage);                   //Free up memory
        }
    }
}

float frand(void) {
    int32_t rv = 0x8000 -(rand()&0xFFFF);
    return (rv*rv/1073741824.0f);
}

int main (void) {
    float RGB1[3];
    float RGB2[3];
    float INC[3];
    led_common = 1;         // for commono anode...
    Thread thread2(led_thread);
//--- Create a random color ---------------------
    for (int x=0; x<3; x++) {
        RGB1[x] = frand();
    }

    while (true) {
//--- Create a new random color -----------------
        for (int x=0; x<3; x++) {
            RGB2[x] = frand();
        }
//--- Determine increments to go from color 1 to color 2 in 25 steps
        for (int x=0; x<3; x++) {
            INC[x] = (RGB1[x] - RGB2[x]) / 25;
        }       
//--- Send color codes to thread2 ---------------
        for (int s=0; s<25; s++) {
            message_t *message = mbox.alloc();      //Allocate memory
            message->red = RGB1[0];
            message->green = RGB1[1];
            message->blue = RGB1[2];
            mbox.put(message);                      //Send data as message
            Thread::wait(100);
            for (int x=0; x<3; x++) {
                RGB1[x] -= INC[x];                  //Approach to second colour
            }
        }
    }
}