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Benjamin Ramhorst
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README.md
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README.md
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The following document outlines the design, implementation and real-time dependecies of a music synthesizer for the 2nd coursework of the Embedded Systems module.
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## System tasks
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The sytem at hand executes several real-time tasks, including:
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*Reading the key matrix
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*Updating the display
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*Generating sound
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The sytem at hand executes several real-time tasks, including:
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* Reading the key matrix
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* Updating the display
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* Generating sound
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### Reading the key matrix
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**Purpose:**
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*Decode the key matrix, obtaining the states of the keys, knobs and joysticks
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*Obtain the currently selected note from the decoded key matrix
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*Select the appopriate step size for the currently selected note
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*Transmit the currently selected note, along side its state (pressed or released) using CAN
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*Obtain any changes in the knobs from the decoded key matrix, corresponding to volume, octave or waveform
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### Reading the key matrix
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**Purpose:**
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* Decode the key matrix, obtaining the states of the keys, knobs and joysticks
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* Obtain the currently selected note from the decoded key matrix
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* Select the appopriate step size for the currently selected note
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* Transmit the currently selected note, along side its state (pressed or released) using CAN
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* Obtain any changes in the knobs from the decoded key matrix, corresponding to volume, octave or waveform
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**Function:** code(void scanKeysTask(void *pvParameters))
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**Implementation:** Thread, executing every 50ms
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**Minimum initiation time:** TO BE COMPLETED.
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**Maximum execution time:** TO BE COMPLETED.
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**Priority:** Highest (1), as playing the appropriate sound is more important than updating the display.
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**Function:** code(void scanKeysTask(void *pvParameters))
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**Implementation:** Thread, executing every 50ms
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**Minimum initiation time:** TO BE COMPLETED.
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**Maximum execution time:** TO BE COMPLETED.
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**Priority:** Highest (1), as playing the appropriate sound is more important than updating the display.
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### Updating the display
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**Purpose:**
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*Display the currently selected note (string)
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*Display the current volume (int)
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*Display the current octave (int)
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*Display the current waveform (XMB icons)
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### Updating the display
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**Purpose:**
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* Display the currently selected note (string)
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* Display the current volume (int)
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* Display the current octave (int)
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* Display the current waveform (XMB icons)
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**Function:** code(displayUpdateTask(void *pvParameters)
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**Implementation:** Thread, executing every 100ms. While a refresh rate of 10Hz does not sound impressive; the display is largely static. Therefore, 100ms was perfectly accetable, without any noticeable delays.
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**Minimum initiation time:** TO BE COMPLETED.
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**Maximum execution time:** TO BE COMPLETED.
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**Priority:** Lowest (2).
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**Function:** code(displayUpdateTask(void *pvParameters)
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**Implementation:** Thread, executing every 100ms. While a refresh rate of 10Hz does not sound impressive; the display is largely static. Therefore, 100ms was perfectly accetable, without any noticeable delays.
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**Minimum initiation time:** TO BE COMPLETED.
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**Maximum execution time:** TO BE COMPLETED.
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**Priority:** Lowest (2).
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### Generating the sound
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**Purpose:**
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*Adds the sample rate to the accumulated value, corresponding to the desired frequency
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*Sets the output voltage, by using the accumlated value and the desired volume
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*Writes to analogue output, generating the desired sound
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### Generating the sound
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**Purpose:**
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* Adds the sample rate to the accumulated value, corresponding to the desired frequency
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* Sets the output voltage, by using the accumlated value and the desired volume
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* Writes to analogue output, generating the desired sound
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**Function:** code(sampleISR())
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**Implementation:** Interrupt executing with a frequency of 44.1kHz
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**Minimum initiation time:** TO BE COMPLETED.
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**Maximum execution time:** TO BE COMPLETED.
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**Function:** code(sampleISR())
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**Implementation:** Interrupt executing with a frequency of 44.1kHz
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**Minimum initiation time:** TO BE COMPLETED.
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**Maximum execution time:** TO BE COMPLETED.
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### CAN
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**Purpose:**
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* TO BE ADDED
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* TO BE ADDED
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**Function:**
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**Implementation:**
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**Minimum initiation time:**
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**Maximum execution time:**
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**Priority:**
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**Function:**
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**Implementation:**
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**Minimum initiation time:**
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**Maximum execution time:**
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**Priority:**
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## Critical instant analysis of the rate monotonic scheduler
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TO BE ADDED - After system is completed.
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## Critical instant analysis of the rate monotonic scheduler
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TO BE ADDED - After system is completed.
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## CPU Resource Usage
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TO BE ADDED - After system is completed; see this link: https://edstem.org/us/courses/19499/discussion/1300057
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## CPU Resource Usage
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TO BE ADDED - After system is completed; see this link: https://edstem.org/us/courses/19499/discussion/1300057
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## Shared data structures
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Shared data structures:
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*code(currentStepSize), safe access guaranteed using code(std::atomic<uint32_t>)
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*code(keyArray), each element within the array is of type code(std::atomic<uint8_t>)
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*msgInQ, handled by FreeRTOS
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*code(RX_Message), handled by code(std::atomic_flag)
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## Shared data structures
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Shared data structures:
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* code(currentStepSize), safe access guaranteed using code(std::atomic<uint32_t>)
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* code(keyArray), each element within the array is of type code(std::atomic<uint8_t>)
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* msgInQ, handled by FreeRTOS
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* code(RX_Message), handled by code(std::atomic_flag)
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It was desiced to use C++ code(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."* (https://en.cppreference.com/w/cpp/atomic/atomic)
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It was desiced to use C++ code(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.*"(https://en.cppreference.com/w/cpp/atomic/atomic)
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TODO - Expand on the memory model for std:: atomic.
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TODO - Explain how FreeRTOS handles msgInQ.
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TODO - Once CAN is completed, expand on the protection of RX_Message
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TODO - Expand on the memory model for std::atomic.
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TODO - Explain how FreeRTOS handles msgInQ.
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TODO - Once CAN is completed, expand on the protection of RX_Message
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## Analysis of inter-task blocking dependencies
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