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Re: Power Distribution Board
June 19, 2024 08:04PM
Implementing cooperative multitasking on AVR microcontrollers like the ATtiny2313 involves setting up a framework where multiple tasks can execute sequentially. Here's a concise step-by-step approach to achieve this:

1. Timer Setup
Utilize one of the timers available on the ATtiny2313, such as Timer/Counter1, to generate periodic interrupts. These interrupts will create a system tick, which forms the basis for task scheduling.

2. Interrupt Service Routine (ISR)
Define an ISR for the timer interrupt (TIMER1_COMPA_vect). This ISR will handle system-level operations like updating the system time or tick counter and performing task switching.

Example ISR structure:

// Update system time or tick counter

// Perform task switching (context switch) if necessary
3. Task Management
Tasks can be managed using a task control block (TCcool smiley structure that contains relevant information for each task, such as its function pointer, execution period, and remaining ticks until next execution.

Example task structure:

typedef struct {
void (*taskFunction)(void); // Pointer to task function
uint16_t period; // Execution period in ticks
uint16_t ticksToNextExecution;// Ticks until next execution
// Add other parameters as needed
} TaskControlBlock;

TaskControlBlock tasks[NUM_TASKS]; // Array of task control blocks
4. Task Scheduler
Create a scheduler function that iterates through the task list and decides whether each task should execute based on its state and the current system time/tick.

Example scheduler:

void scheduler(void) {
for (int i = 0; i < NUM_TASKS; ++i) {
if (tasks.ticksToNextExecution == 0) {
tasks.taskFunction(); // Execute the task
tasks.ticksToNextExecution = tasks.period;
} else {
5. Main Function or Main Loop
In your main() function or main loop, initialize tasks, start the timer, and enable global interrupts. Continuously call the scheduler function or wait for interrupts, depending on your design.

Example main loop:

int main(void) {
// Initialize tasks, timers, etc.

// Enable global interrupts

while (1) {
scheduler(); // Call the scheduler
// Optionally add other tasks or operations here

return 0;
Additional Considerations
Stack Management: Ensure each task has sufficient stack space allocated to prevent stack overflow.
Task Synchronization: Use synchronization techniques like semaphores or flags for inter-task communication if needed.
Interrupt Safety: Ensure that shared resources are accessed safely from both tasks and the ISR.
By following these steps, you can effectively implement cooperative multitasking on an ATtiny2313 AVR microcontroller, enabling efficient task scheduling and execution without the complexity of preemptive multitasking. Adjustments may be required based on specific project requirements and hardware constraints.

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