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DavidAmor-Segan 2022-03-25 23:09:27 +00:00 committed by Aadi Desai
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@ -124,11 +124,14 @@ Therefore, total latency is slightly over 23.07ms. The exact latency could not b
The total CPU usage is calculated by dividing the total latency by the highest initiation time. In this case the CPU usage is ~25%.
## Shared data structures
## Shared data structures & dependencies
* `currentStepSize`, safe access guaranteed using `std::atomic<uint32_t>`, stores the step size of the most recently pressed key, to be used within `sampleISR()`
* `keyArray`, each element within the array is of type `std::atomic<uint8_t>`, stores the current state of the key / encoder matrix
* `msgInQ`, handled by FreeRTOS, pointer to the next item in the received CAN message queue
* `latestKey`, guarded by `std::atomic<int>`, ensures that the current note is maintained as an integer value
* `selectedWaveform` is an int (`std::atomic<uint32_t>`) corresponding to the currently selected Waveform type, that determined if the output is a Sawtooth, Square, Triangle or Sine wave.
* `octave` is modified when the key is changed and the message displayed on the screen needs to be displayed, stored as an int.
It was decided to use C++ `std::atomic`, as it is easier to use and implement, while providing the same functionality as a mutex. According to the documentation: *"Each instantiation and full specialization of the std::atomic template defines an atomic type. If one thread writes to an atomic object while another thread reads from it, the behavior is well-defined (see memory model for details on data races). In addition, accesses to atomic objects may establish inter-thread synchronization and order non-atomic memory accesses as specified by std::memory_order.*" - [CPP Reference "std::atomic"](https://en.cppreference.com/w/cpp/atomic/atomic)
@ -136,6 +139,8 @@ It was decided to use C++ `std::atomic`, as it is easier to use and implement, w
`msgInQ` is used as a FIFO buffer for CAN messages, to supplement the small buffer of the CAN system and allow for more messages to be retained, increasing the required minimum initiation time.
![Dependency Graph](docs/DependencyGraph.png)
## Analysis of inter-task blocking dependencies
## Advanced features

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