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README.md
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@ -3,17 +3,17 @@ The following document outlines the design, implementation and real-time depende
## System tasks
The sytem at hand executes several real-time tasks, including:
*Reading the key matrix
*Updating the display
*Generating sound
* Reading the key matrix
* Updating the display
* Generating sound
### Reading the key matrix
**Purpose:**
*Decode the key matrix, obtaining the states of the keys, knobs and joysticks
*Obtain the currently selected note from the decoded key matrix
*Select the appopriate step size for the currently selected note
*Transmit the currently selected note, along side its state (pressed or released) using CAN
*Obtain any changes in the knobs from the decoded key matrix, corresponding to volume, octave or waveform
* Decode the key matrix, obtaining the states of the keys, knobs and joysticks
* Obtain the currently selected note from the decoded key matrix
* Select the appopriate step size for the currently selected note
* Transmit the currently selected note, along side its state (pressed or released) using CAN
* Obtain any changes in the knobs from the decoded key matrix, corresponding to volume, octave or waveform
**Function:** code(void scanKeysTask(void *pvParameters))
**Implementation:** Thread, executing every 50ms
@ -23,10 +23,10 @@ The sytem at hand executes several real-time tasks, including:
### Updating the display
**Purpose:**
*Display the currently selected note (string)
*Display the current volume (int)
*Display the current octave (int)
*Display the current waveform (XMB icons)
* Display the currently selected note (string)
* Display the current volume (int)
* Display the current octave (int)
* Display the current waveform (XMB icons)
**Function:** code(displayUpdateTask(void *pvParameters)
**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.
@ -36,9 +36,9 @@ The sytem at hand executes several real-time tasks, including:
### Generating the sound
**Purpose:**
*Adds the sample rate to the accumulated value, corresponding to the desired frequency
*Sets the output voltage, by using the accumlated value and the desired volume
*Writes to analogue output, generating the desired sound
* Adds the sample rate to the accumulated value, corresponding to the desired frequency
* Sets the output voltage, by using the accumlated value and the desired volume
* Writes to analogue output, generating the desired sound
**Function:** code(sampleISR())
**Implementation:** Interrupt executing with a frequency of 44.1kHz
@ -63,14 +63,14 @@ TO BE ADDED - After system is completed; see this link: https://edstem.org/us/co
## Shared data structures
Shared data structures:
*code(currentStepSize), safe access guaranteed using code(std::atomic<uint32_t>)
*code(keyArray), each element within the array is of type code(std::atomic<uint8_t>)
*msgInQ, handled by FreeRTOS
*code(RX_Message), handled by code(std::atomic_flag)
* code(currentStepSize), safe access guaranteed using code(std::atomic<uint32_t>)
* code(keyArray), each element within the array is of type code(std::atomic<uint8_t>)
* msgInQ, handled by FreeRTOS
* code(RX_Message), handled by code(std::atomic_flag)
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)
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)
TODO - Expand on the memory model for std:: atomic.
TODO - Expand on the memory model for std::atomic.
TODO - Explain how FreeRTOS handles msgInQ.
TODO - Once CAN is completed, expand on the protection of RX_Message