Hi all,
I try to implement a doubly linked-list that holds task control blocks (TCBs), each of which contains a pointer to function and a void pointer. I write a sketch to perform blinking led but nothing happens. My sketch is as follows:
#include <scheduler.h>
Queue *q;
TCB *currentTask;
void blinking(void *data) {
digitalWrite(13, HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000); // wait for a second
digitalWrite(13, LOW); // turn the LED off by making the voltage LOW
delay(1000); // wait for a second
}
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin 13 as an output.
pinMode(13, OUTPUT);
q->QueueInsert(NULL, blinking);
currentTask = q->head;
}
// the loop function runs over and over again forever
void loop() {
currentTask->function(currentTask->data);
}
scheduler.h:
#ifndef SCHEDULER_H_
#define SCHEDULER_H_
#include "stdlib.h"
typedef void (*task)(void *data);
class TCB {
public:
void *data;
TCB *next;
TCB *prev;
public:
void (*function)(void *);
};
class Queue {
public:
TCB *head;
TCB *tail;
int count;
public:
void QueueInsert(void *data, task myTask);
void QueueRemove(TCB *task);
};
#endif
scheduler.cpp:
[/code]
#include “scheduler.h”
// Insert at tail
void Queue::QueueInsert(void *value, task myTask)
{
TCB newTask = (TCB)calloc(1, sizeof(TCB));
newTask->data = value;
newTask->function = myTask;
if(head == NULL) {
head = newTask;
tail = newTask;
} else {
tail->next = newTask;
newTask->prev = tail;
tail = newTask;
}
count++;
}
// Remove a particular node in queue
void Queue::QueueRemove(TCB *task)
{
if(head == NULL) {
// do nothing
}
if(task == head && task == tail) {
head = NULL;
tail = NULL;
} else if(task == head) {
head = task->next;
head->prev = NULL;
} else if(task == tail) {
tail = task->prev;
tail->next = NULL;
} else {
TCB *after = task->next;
TCB *before = task->prev;
after->prev = before;
before->next = after;
}
count–;
free(task);
}
[/code]
