This example describes how to use mailbox in CORTEX-M4.We have used Cortex m4 development board

Procedure for mailbox using Cortex m4

1. Initialize UART0 @9600 baud rate
2. Create a Send Task and a receive Task
3. Compose and send the mailbox data using send task
4. Discard send task and free-up memories
5. Retrieve the messages using receive task

Mailbox using Cortex M4-C Source code

#include <RTL.h>                      /* RTX kernel functions & defines      */
#include <LPC407x_8x_177x_8x.h>
#include "uart0.h"

OS_TID tsk1;                          /* assigned identification for task 1  */
OS_TID tsk2;                          /* assigned identification for task 2  */

typedef struct {                      /* Message object structure            */
  int voltage;                      /* AD result of measured voltage       */
  int current;                      /* AD result of measured current       */
  U32   counter;                      /* A counter value                     */
} T_MEAS;

os_mbx_declare (MsgBox,16);           		/* Declare an RTX mailbox              */
_declare_box (mpool,sizeof(T_MEAS),16);		/* Dynamic memory pool                */

__task void send_task (void);
__task void rec_task (void);

unsigned char str[6];


/*----------------------------------------------------------------------------
 *  Task 1:  RTX Kernel starts this task with os_sys_init (send_task)
 *---------------------------------------------------------------------------*/
__task void send_task (void) {
	  T_MEAS *mptr;

	  tsk1 = os_tsk_self ();              						/* get own task identification number  */
		//2. Create receive Task
	  tsk2 = os_tsk_create (rec_task, 0); 						/* start task 2                        */
	  os_mbx_init (MsgBox, sizeof(MsgBox));						/* initialize the mailbox             */
	  os_dly_wait (5);                    						/* Startup delay for MCB21xx           */

		//3.Compose a mail of data
	  mptr = _alloc_box (mpool);          						/* Allocate a memory for the message   */
	  mptr->voltage = 223;             								/* Set the message content             */
	  mptr->current = 17;
	  mptr->counter = 1207;
	  os_mbx_send (MsgBox, mptr, 0xffff); 						/* Send the message to the mailbox     */
	  os_dly_wait (100);

	  mptr = _alloc_box (mpool);
	  mptr->voltage = 227;             								/* Prepare a 2nd message               */
	  mptr->current = 12;
	  mptr->counter = 1708;
	  os_mbx_send (MsgBox, mptr, 0xffff); 						/* And send it.                        */
	  os_tsk_pass ();                     						/* Cooperative multitasking            */
	  os_dly_wait (100);

	  mptr = _alloc_box (mpool);
	  mptr->voltage = 229;             								/* Prepare a 3rd message               */
	  mptr->current = 11;
	  mptr->counter = 2371;
		//3. Send the Mail of data
	  os_mbx_send (MsgBox, mptr, 0xffff); 						/* And send it.                        */
	  os_dly_wait (100);
		
		//4. Discard the send task
	  os_tsk_delete_self ();              						/* We are done here, delete this task  */
}

/*----------------------------------------------------------------------------
 *  Task 2: RTX Kernel starts this task with os_tsk_create (rec_task, 0)
 *---------------------------------------------------------------------------*/
__task void rec_task (void) {
  T_MEAS *rptr;
	//5. Retrieve the mail of data and display it in UART
  for (;;) 
	{
		os_mbx_wait (MsgBox, (void **)&rptr, 0xffff); 				/* wait for the message    */
		UART0_puts((unsigned char *)"\r\nVoltage:");
		itoa(rptr->voltage,str);
		UART0_puts(str);
		
		UART0_puts((unsigned char *)"\r\nCurrent:");
		itoa(rptr->current,str);
		UART0_puts(str);
		
		UART0_puts((unsigned char *)"\r\nNumber of cycles:");
		itoa(rptr->counter,str);
		UART0_puts(str);
		
		_free_box (mpool, rptr);           										/* free memory allocated for message  */
  }
}

/*----------------------------------------------------------------------------
 *        Main: Initialize and start RTX Kernel
 *---------------------------------------------------------------------------*/
int main (void) 
{ 
		//1. Initialize Serial Port
		init_serial();                     		/* initialize the serial interface     */
		_init_box (mpool, sizeof(mpool),    	/* initialize the 'mpool' memory for   */
								sizeof(T_MEAS));        	/* the membox dynamic allocation       */
		//2. Create and Initialize the Send Task
		os_sys_init (send_task);            	/* initialize and start task 1         */
}


/*----------------------------------------------------------------------------
 * end of file
 *---------------------------------------------------------------------------*/