mailbox

Example Summary

The mailbox example shows how to use the ti.sysbios.knl.Mailbox module which addresses the problem of a task needing to wait on data before continuing its execution.

Example Usage

• Run the application. Two tasks, writerTask and readerTask, will print messages being passed between them to the console.

Application Design Details

• A MsgObj struct is defined to be used for messages in this example. The struct contains two data members: id and val. In readerTask and writerTask, a local MsgObj is declared to store the mailbox data. When using Mailbox_post or Mailbox_pend, the local MsgObj msg is copied to or from the internal mailbox buffer, respectively. When changing the data members of this structure, considerations should be made for padding and data alignment.

• A MailboxMsgObj struct is defined to be used for the mailbox buffer. The struct contains two data members: Mailbox_MbxElem elem and MsgObj obj. Mailbox messages are stored in a queue that requires a header in front of each message. Mailbox_MbxElem is defined such that the header and its size are factored into the total data size requirement for a mailbox instance. Because Mailbox_MbxElem contains Int data types, padding may be added to this struct depending on the data members defined in MsgObj.

The application is responsible for ensuring the buffer supplied is of sufficient size.

• A writer task, writerTask, is responsible for putting messages into the mailbox. It loops for NUMMSGS iterations; placing a message in the mailbox. The values that are put in the mailbox are also print to the console.

• A reader task, readerTask, is responsible for reading messages from the mailbox. It loops for NUMMSGS iterations; blocking indefinitely until a message is available to read. The values read are printed to the console.

In this example, only one task is writing messages to the mailbox. However, it is possible that multiple tasks can write messages to the same mailbox instance.

References

• For GNU and IAR users, please read the following website for details about enabling semi-hosting in order to view console output.

• For more help, search the SYS/BIOS User Guide.