README.md

Learning Objectives

• Stream Buffer.

Concepts

Stream buffers are inter-task communication primitives to allow a stream of bytes to be passed from an interrupt service routine to a task, or from one task to another task. A byte stream can be of arbitrary length and does not necessarily have a beginning or end.

IMPORTANT NOTE: The stream buffer implementation assumes there is only one task or interrupt that will write to the buffer (the writer), and only one task or interrupt that will read from the buffer (the reader).

The amount of data that must be in the stream buffer before a task that is waiting for data, is removed from the blocked state is called the stream buffer's Trigger Level. For example:

• If a task is blocked on a read of an empty stream buffer that has a trigger level of 1 then the task will be unblocked when a single byte is written to the buffer or the task's block time expires.
• If a task is blocked on a read of an empty stream buffer that has a trigger level of 10 then the task will not be unblocked until the stream buffer contains at least 10 bytes or the task's block time expires.

If a reading task's block time expires before the trigger level is reached then the task will still receive however many bytes are actually available.

Steps

1. Complete all the TODOs in the source/tutorials/tutorial_19/source/tutorial_19.c file.

2. Execute the following commands from the root of the repository to build:

   rm -rf build
   mkdir build
   cd build
   cmake -B . -S ../source/ -DTUTORIAL=19
   make

3. Execute the following command to run the binary:

   ./freertos_example

4. Understand the output.