dheeptuck

void CustomMallocInit(HEAP_INFO_t *pHeapInfo)
{
    pHeapInfo->alloc_dll = &(pHeapInfo->dummy1);
    pHeapInfo->alloc_dll->next = NULL;
    pHeapInfo->alloc_dll->prev = NULL;
    pHeapInfo->avail_dll = &(pHeapInfo->dummy2);
    pHeapInfo->avail_dll->prev = NULL;
    pHeapInfo->avail_dll->next = pHeapInfo->pHeap;
    pHeapInfo->avail_dll->next->blkSize = pHeapInfo->heapSz - sizeof(BD_t);
    pHeapInfo->avail_dll->next->next = NULL;

dheeptuck

/*
 * Initializes the heap. It internally created a BD and places at start of the
 * heap. The BD is added to avail_dll.
 * @param pHeapInfo: Pointer to the current heap info.
 **/
void CustomMallocInit(HEAP_INFO_t *pHeapInfo);

/*
 * Mimics the malloc function(i.e provides the requested memory). Returns NULL in
 * case is it not possible to allocate the requested memory.

dheeptuck

typedef struct BD_t
{
    int blkSize;
    struct BD_t *prev;
    struct BD_t *next;
} BD_t;

dheeptuck

/*
 * premptive_scheduler.c
 *
 *  Created on: Apr 26, 2020
 *      Author: Sudeep Chandrasekaran
 */
#include <stdint.h>
#include <stdbool.h>
#include "premptive_scheduler.h"

dheeptuck

void portable_delay_cycles(unsigned long n)
{
 	while (n--)
 	{
 		asm volatile ("");
 	}
}

volatile void Task0()
{

dheeptuck

__attribute__((naked)) void LaunchScheduler(void)
{
    /// R0 contains the address of currentPt
    __asm("LDR     R0, =pCurntTcb");
    /// R2 contains the address in currentPt(value of currentPt)
    __asm("LDR     R2, [R0]");
    /// Load the SP reg with the stacked SP value
    __asm("LDR     R4, [R2]");
    __asm("MOV     SP, R4");
    /// Pop registers R8-R11(user saved context)

dheeptuck

void OsInitThreadStack()
{
	/// Enter critical section
	/// Disable interrupts
	__asm("CPSID   I");
	/// Make the TCB linked list circular
	tcbs[0].nextPt = &tcbs[1];
	tcbs[1].nextPt = &tcbs[0];

	/// Setup stack for task0

dheeptuck

__attribute__((naked)) void SysTick_Handler(void)
{
	/// STEP 1 - SAVE THE CURRENT TASK CONTEXT

	/// At this point the processor has already pushed PSR, PC, LR, R12, R3, R2, R1 and R0
	/// onto the stack. We need to push the rest(i.e R4, R5, R6, R7, R8, R9, R10 & R11) to save the
	/// context of the current task.
	/// Disable interrupts
    __asm("CPSID   I");
    /// Push registers R4 to R7

dheeptuck

int main()
{
    while(1)
    {
        LED1_TURN_ON();
        LED2_TURN_ON();
        
        delay_seconds(1);
        
        LED1_TURN_OFF();

dheeptuck

void PumpTask()
{
    while(1)
    {
        if(GetTimeSinceLastToggle() ≥ 30)
        {
            TurnPumpOn();
        }
    }
}