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Online Training Session: Messages for Intertask Communication
| How does a Task Send a Message? |
| 1. Define Content and Structure of the Message • Make Sure Sender and Receiver Tasks have Same Definition 2. Allocate a Buffer for Message of appropriate size 3. Fill in the Data Payload of the Message 4. Send the Message • “Indirect” Message Passing RTOSs: Send to a predefined Queue • “Direct” Message Passing RTOSs: Send to Receiver Task 5. Make Sure the Buffer is eventually Freed • “Indirect” Message Passing RTOSs: Sender Task frees buffer • “Direct” Message Passing RTOSs: Receiver Task frees buffer |
| NOTES: This is a 5-step "cookbook" for what to do to program a task to send a message. The details are slightly different for different off-the-shelf RTOSs and RTOS categories. FOR INDIRECT MESSAGE PASSING RTOSs 1. Define Content and Structure of the Message • Make Sure Sender and Receiver Tasks have Same Definition 2. Allocate a Buffer for Message of appropriate size 3. Fill in the Data Payload of the Message 4. Send the Message to a predefined Queue 5. Make Sure the Buffer is eventually Freed by the Sender Task FOR DIRECT MESSAGE PASSING RTOSs 1. Define Content and Structure of the Message • Make Sure Sender and Receiver Tasks have Same Definition 2. Allocate a Buffer for Message of appropriate size 3. Fill in the Data Payload of the Message 4. Send the Message to the Receiver Task 5. Make Sure the Buffer is eventually Freed by the Receiver Task • Sender Task does not free buffer (when message is passed by pointer) |
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