Andy A / Mbed 2 deprecated SimpleTaskSwitchDemo

Simple example of a very basic cooperative round robin task switching.

Dependencies:   mbed

A very basic demo of how to run a set of tasks in sequence.

main.cpp@0:301a83d3eeb4, 2015-03-19 (annotated)

Committer:
AndyA
Date:
Thu Mar 19 17:08:55 2015 +0000
Revision:
0:301a83d3eeb4
First commit.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
AndyA 0:301a83d3eeb4 1 #include "mbed.h"
AndyA 0:301a83d3eeb4 2
AndyA 0:301a83d3eeb4 3 Serial pc(USBTX,USBRX);
AndyA 0:301a83d3eeb4 4
AndyA 0:301a83d3eeb4 5 int taskCount = 0;
AndyA 0:301a83d3eeb4 6 const int maxTasks = 16;
AndyA 0:301a83d3eeb4 7 void *taskList[maxTasks];
AndyA 0:301a83d3eeb4 8
AndyA 0:301a83d3eeb4 9 typedef void function_t(void);
AndyA 0:301a83d3eeb4 10
AndyA 0:301a83d3eeb4 11 //runs the next task. Avoid calling from a ticker since that would block all interrupts while running.
AndyA 0:301a83d3eeb4 12 void nextTask(void)
AndyA 0:301a83d3eeb4 13 {
AndyA 0:301a83d3eeb4 14 static int taskID = 0;
AndyA 0:301a83d3eeb4 15 if (taskCount) {
AndyA 0:301a83d3eeb4 16 if (taskID >= taskCount) // a task could have been removed.
AndyA 0:301a83d3eeb4 17 taskID = 0;
AndyA 0:301a83d3eeb4 18
AndyA 0:301a83d3eeb4 19 ((function_t*)taskList[taskID])();
AndyA 0:301a83d3eeb4 20 taskID++;
AndyA 0:301a83d3eeb4 21 if (taskID == taskCount)
AndyA 0:301a83d3eeb4 22 taskID = 0;
AndyA 0:301a83d3eeb4 23 }
AndyA 0:301a83d3eeb4 24 }
AndyA 0:301a83d3eeb4 25
AndyA 0:301a83d3eeb4 26 // add a task to the list
AndyA 0:301a83d3eeb4 27 bool addTask(void (*function)(void))
AndyA 0:301a83d3eeb4 28 {
AndyA 0:301a83d3eeb4 29 if ((taskCount < maxTasks) && function) {
AndyA 0:301a83d3eeb4 30 taskList[taskCount] = (void *)function;
AndyA 0:301a83d3eeb4 31 taskCount++;
AndyA 0:301a83d3eeb4 32 return true;
AndyA 0:301a83d3eeb4 33 } else
AndyA 0:301a83d3eeb4 34 return false;
AndyA 0:301a83d3eeb4 35 }
AndyA 0:301a83d3eeb4 36
AndyA 0:301a83d3eeb4 37 // finds a task in the list or -1 if not in the list. Mainly used for removing tasks.
AndyA 0:301a83d3eeb4 38 int findTask(void (*function)(void))
AndyA 0:301a83d3eeb4 39 {
AndyA 0:301a83d3eeb4 40 if (!function)
AndyA 0:301a83d3eeb4 41 return -1;
AndyA 0:301a83d3eeb4 42 int number = 0;
AndyA 0:301a83d3eeb4 43 while (number < taskCount) {
AndyA 0:301a83d3eeb4 44 if (taskList[number] == (void *)function)
AndyA 0:301a83d3eeb4 45 return number;
AndyA 0:301a83d3eeb4 46 number++;
AndyA 0:301a83d3eeb4 47 }
AndyA 0:301a83d3eeb4 48 return -1;
AndyA 0:301a83d3eeb4 49 }
AndyA 0:301a83d3eeb4 50
AndyA 0:301a83d3eeb4 51 // remove a task. returns false if the task wasn't in the list.
AndyA 0:301a83d3eeb4 52 bool removeTask(void (*function)(void))
AndyA 0:301a83d3eeb4 53 {
AndyA 0:301a83d3eeb4 54 int taskToRemove = findTask(function);
AndyA 0:301a83d3eeb4 55 if (taskToRemove == -1)
AndyA 0:301a83d3eeb4 56 return false;
AndyA 0:301a83d3eeb4 57
AndyA 0:301a83d3eeb4 58 for (int i = taskToRemove; i<(taskCount-1); i++) {
AndyA 0:301a83d3eeb4 59 taskList[i] = taskList[i+1];
AndyA 0:301a83d3eeb4 60 }
AndyA 0:301a83d3eeb4 61 taskCount--;
AndyA 0:301a83d3eeb4 62 return true;
AndyA 0:301a83d3eeb4 63 }
AndyA 0:301a83d3eeb4 64
AndyA 0:301a83d3eeb4 65 // simple example task.
AndyA 0:301a83d3eeb4 66 void task1(void)
AndyA 0:301a83d3eeb4 67 {
AndyA 0:301a83d3eeb4 68 const int NumberOfStates = 5;
AndyA 0:301a83d3eeb4 69 static int state = 0;
AndyA 0:301a83d3eeb4 70 switch (state) {
AndyA 0:301a83d3eeb4 71 case 0:
AndyA 0:301a83d3eeb4 72 pc.putc('A');
AndyA 0:301a83d3eeb4 73 break;
AndyA 0:301a83d3eeb4 74 case 1:
AndyA 0:301a83d3eeb4 75 pc.putc('B');
AndyA 0:301a83d3eeb4 76 break;
AndyA 0:301a83d3eeb4 77 case 2:
AndyA 0:301a83d3eeb4 78 pc.putc('C');
AndyA 0:301a83d3eeb4 79 break;
AndyA 0:301a83d3eeb4 80 case 3:
AndyA 0:301a83d3eeb4 81 pc.putc('D');
AndyA 0:301a83d3eeb4 82 break;
AndyA 0:301a83d3eeb4 83 case 4:
AndyA 0:301a83d3eeb4 84 pc.putc('E');
AndyA 0:301a83d3eeb4 85 break;
AndyA 0:301a83d3eeb4 86 default:
AndyA 0:301a83d3eeb4 87 state = 0;
AndyA 0:301a83d3eeb4 88 break;
AndyA 0:301a83d3eeb4 89 }
AndyA 0:301a83d3eeb4 90 state++;
AndyA 0:301a83d3eeb4 91 if (state == NumberOfStates)
AndyA 0:301a83d3eeb4 92 state = 0;
AndyA 0:301a83d3eeb4 93 }
AndyA 0:301a83d3eeb4 94
AndyA 0:301a83d3eeb4 95 // simple example task.
AndyA 0:301a83d3eeb4 96 void task2(void)
AndyA 0:301a83d3eeb4 97 {
AndyA 0:301a83d3eeb4 98 const int NumberOfStates = 2;
AndyA 0:301a83d3eeb4 99 static int state = 0;
AndyA 0:301a83d3eeb4 100 switch (state) {
AndyA 0:301a83d3eeb4 101 case 0:
AndyA 0:301a83d3eeb4 102 pc.putc('1');
AndyA 0:301a83d3eeb4 103 break;
AndyA 0:301a83d3eeb4 104 case 1:
AndyA 0:301a83d3eeb4 105 pc.putc('2');
AndyA 0:301a83d3eeb4 106 break;
AndyA 0:301a83d3eeb4 107 default:
AndyA 0:301a83d3eeb4 108 state = 0;
AndyA 0:301a83d3eeb4 109 break;
AndyA 0:301a83d3eeb4 110 }
AndyA 0:301a83d3eeb4 111 state++;
AndyA 0:301a83d3eeb4 112 if (state == NumberOfStates)
AndyA 0:301a83d3eeb4 113 state = 0;
AndyA 0:301a83d3eeb4 114 }
AndyA 0:301a83d3eeb4 115
AndyA 0:301a83d3eeb4 116 // simple example task using enum for current state.
AndyA 0:301a83d3eeb4 117 void task3(void)
AndyA 0:301a83d3eeb4 118 {
AndyA 0:301a83d3eeb4 119 static enum {firstState,secondState} state = firstState;
AndyA 0:301a83d3eeb4 120 switch (state) {
AndyA 0:301a83d3eeb4 121 case firstState:
AndyA 0:301a83d3eeb4 122 pc.putc('X');
AndyA 0:301a83d3eeb4 123 state = secondState;
AndyA 0:301a83d3eeb4 124 break;
AndyA 0:301a83d3eeb4 125 case secondState:
AndyA 0:301a83d3eeb4 126 pc.putc('Y');
AndyA 0:301a83d3eeb4 127 state = firstState;
AndyA 0:301a83d3eeb4 128 break;
AndyA 0:301a83d3eeb4 129 default:
AndyA 0:301a83d3eeb4 130 state = firstState;
AndyA 0:301a83d3eeb4 131 break;
AndyA 0:301a83d3eeb4 132 }
AndyA 0:301a83d3eeb4 133 }
AndyA 0:301a83d3eeb4 134
AndyA 0:301a83d3eeb4 135 main ()
AndyA 0:301a83d3eeb4 136 {
AndyA 0:301a83d3eeb4 137
AndyA 0:301a83d3eeb4 138 addTask(&task1);
AndyA 0:301a83d3eeb4 139 addTask(&task2);
AndyA 0:301a83d3eeb4 140 pc.printf("\r\nTasks 1 & 2\r\n");
AndyA 0:301a83d3eeb4 141 for (int i = 0; i < 20; i++)
AndyA 0:301a83d3eeb4 142 nextTask();
AndyA 0:301a83d3eeb4 143
AndyA 0:301a83d3eeb4 144
AndyA 0:301a83d3eeb4 145 addTask(&task1);
AndyA 0:301a83d3eeb4 146 addTask(&task3);
AndyA 0:301a83d3eeb4 147 pc.printf("\r\nTasks 1,2,1,3\r\n");
AndyA 0:301a83d3eeb4 148 for (int i = 0; i < 20; i++)
AndyA 0:301a83d3eeb4 149 nextTask();
AndyA 0:301a83d3eeb4 150
AndyA 0:301a83d3eeb4 151 removeTask(&task1); // removes the first instance of task 1 in the list.
AndyA 0:301a83d3eeb4 152 pc.printf("\r\nTasks 2,1,3\r\n");
AndyA 0:301a83d3eeb4 153 for (int i = 0; i < 20; i++)
AndyA 0:301a83d3eeb4 154 nextTask();
AndyA 0:301a83d3eeb4 155
AndyA 0:301a83d3eeb4 156 pc.printf("\r\nDone\r\n");
AndyA 0:301a83d3eeb4 157
AndyA 0:301a83d3eeb4 158 }