OCEOS Tutorials
Revision as of 10:58, 25 February 2022 by Dtimofejevs (talk | contribs) (→Tutorial 4 – Timer interrupt starts task)
Tutorials
Introduction
This section presents some typical real-time tasks and how they can be addressed using OCEOS.
Getting started
Section 9.5 provides guidance on how to structure an OCEOS application. The file asw.c provided with OCEOS is a simple example.
The directives to initialise and start OCEOS are:
- application_init – Initialise fixed data and start system timer(s)
- oceos_task_create - Create task setting priority, no of jobs, ..etc.
- oceos_init_finish – Initilise dynamic data area
- oceos_start – Start the scheduler and pass control to first task
After steps 1 to 4 above tasks implement application functionality. If mutexes, semaphores, or dataqs are required they are also created at step 2.
Note: it is mandatory to create the number of mutexes, semaphores, and dataqs declared otherwise oceos_init_finish() will return an error.
Tutorials
Tutorial 1 – Starting tasks
This exercise demonstrates starting tasks with different priorities.
- Two tasks, one higher priority (i.e. lower priority value), one lower priority (i.e. higher priority value. Each task allowed to have up to two concurrent jobs.
- Each task outputs a message when it starts, another message when it exits.
- Start OCEOS with the low priority task.
- This starts the high priority task and then exits.
- The high priority task starts the low priority tasks and exits.
For code example see below.
1 /*
2 *********************************************************************************************************
3 * OCEOS
4 * Real-Time Operating System
5 * for
6 * ARM Microcontroller
7 *
8 * Example implementation of OCEOS
9 *
10 *
11 * (c) Copyright 2021, O.C.E. Technology
12 * All Rights Reserved
13 *
14 *
15 * Author: jfk
16 ********************************************************************************************************
17 */
18 #include <stdio.h>
19 #include <stdlib.h>
20 #include "tut1.h" // application header
21 #include "oceos_config.h" // OCEOS header
22
23 int main(void) {
24 int status;
25
26 /*
27 * Initialise the application configuration and OCEOS
28 *
29 * This application function creates the application configuration
30 * and passes it to oceos_init(), which initialises the fixed data
31 * and enables the system log
32 */
33 if (!application_init()) {
34 //LOG
35 return -1;
36 }
37
38 // Create Main task to
39 if (oceos_task_create(t_0,// taskID, used as index, must be in range 0 to 254
40 100,// priority, must be in range 1 to 254, lower value is higher priority
41 100, // threshold, must be in range 1 to task priority
42 2, // jobs_max, must be in range 1 to 15
43 0,// FALSE -> floating point hardware not used by task
44 1, // FALSE -> task initially not enabled
45 fun0, // main body of task
46 nullFun, // task end function
47 0,// time_deadline, must finish no later than this after start, 0 => ignore
48 0 // minimum time expected between start requests, 0 => no restriction
49 ) != SUCCESSFUL)
50 return 1;
51
52 if (oceos_task_create(t_1, 200, 200, 2, 0, 1, fun1, nullFun, 0, 0)
53 != SUCCESSFUL)
54 return 2;
55
56 /*
57 * Finish initialising OCEOS and setting up the fixed data
58 */
59 status = oceos_init_finish();
60 if (SUCCESSFUL != status) {
61 return 3;
62 } // if
63
64 /*
65 * Start OCEOS scheduling
66 *
67 * The OCEOS fixed data provides all the information required.
68 *
69 * If a valid task is specified, it is started and passed the pointer.
70 * Otherwise the system is put in sleep mode
71 */
72 status = oceos_start(fixed_data, t_1, (void*) nullPtr); // Start OCEOS with lower prioroty task
73 return status;
74 } // main
75
76 /*
77 * Application code functions, functions declared in asw.h
78 */
79 void fun0(void *ptr) {
80 printf("Entered high priority task\n");
81 oceos_task_start(t_1, ptr);
82 printf("Leaving high priority task\n");
83 return;
84 } // fun0()
85
86 void fun1(void *ptr) {
87 printf("Entered low priority task\n");
88 oceos_task_start(t_0, ptr);
89 printf("Leaving low priority task\n");
90 return;
91 } // fun1()
Tutorial 2 – Using a mutex
This exercise will familiarise the developer with the use a mutexes.
- Two tasks as before.
- One mutex. Note the priority ceiling of the mutex..
- Both tasks output message when they get the mutex and when they return it
- Start OCEOS with the low priority task
- This grabs mutex, then starts high priority task
- Low priority task returns mutex then exits
- High priority task returns mutex, start low priority task and exits
For code example see example below:
1 /*
2 *********************************************************************************************************
3 * OCEOS
4 * Real-Time Operating System
5 * for
6 * ARM Microcontroller
7 *
8 * Example implementation of OCEOS
9 *
10 *
11 * (c) Copyright 2021, O.C.E. Technology
12 * All Rights Reserved
13 *
14 *
15 * Author: jfk
16 ********************************************************************************************************
17 */
18 #include <stdio.h>
19 #include <stdlib.h>
20 #include "tut2.h" // application header
21
22 /* N.B. Application header is included first */
23 #include "oceos_config.h" // OCEOS header for this application
24 #include "mutex.h"
25
26 int main(void) {
27 int status;
28
29 /*
30 * Initialise the application configuration and OCEOS
31 *
32 * This application function creates the application configuration
33 * and passes it to oceos_init(), which initialises the fixed data
34 * and enables the system log
35 */
36 if (!application_init()) {
37 //LOG
38 return -1;
39 }
40
41 // Create Main task to
42 if (oceos_task_create(t_0,// taskID, used as index, must be in range 0 to 254
43 100,// priority, must be in range 1 to 254, lower value is higher priority
44 100, // threshold, must be in range 1 to task priority
45 2, // jobs_max, must be in range 1 to 15
46 0,// FALSE -> floating point hardware not used by task
47 1, // FALSE -> task initially not enabled
48 fun0, // main body of task
49 nullFun, // task end function
50 0,// time_deadline, must finish no later than this after start, 0 => ignore
51 0 // minimum time expected between start requests, 0 => no restriction
52 ) != SUCCESSFUL)
53 return 1;
54
55 if (oceos_task_create(t_1, 200, 200, 2, 0, 1, fun1, nullFun, 0, 0)
56 != SUCCESSFUL)
57 return 2;
58
59 if (oceos_mutex_create(m_0, 100) != SUCCESSFUL) // Create mutex with ceiling of highest priority task using it
60 return 3;
61
62 /*
63 * Finish initialising OCEOS and setting up the fixed data
64 */
65 status = oceos_init_finish();
66 if (SUCCESSFUL != status) {
67 return 4;
68 } // if
69
70 /*
71 * Start OCEOS scheduling
72 *
73 * The OCEOS fixed data provides all the information required.
74 *
75 * If a valid task is specified, it is started and passed the pointer.
76 * Otherwise the system is put in sleep mode
77 */
78 status = oceos_start(fixed_data, t_1, (void*) nullPtr); // Start OCEOS with lower prioroty task
79 return status;
80 } // main
81
82 /*
83 * Application code functions, functions declared in asw.h
84 */
85 void fun0(void *ptr) {
86 if (oceos_mutex_wait(m_0) != SUCCESSFUL) {
87 printf("Error from high priority task getting mutex\n");
88 } else {
89 printf("high priority task got mutex\n");
90 }
91 oceos_task_start(t_1, ptr); // Start lower priority task
92
93 if (oceos_mutex_signal(m_0) != SUCCESSFUL) {
94 printf("Error from high priority task releasing mutex\n");
95 } else {
96 printf("High priority task released mutex\n");
97 }
98 return;
99 } // fun0()
100
101 void fun1(void *ptr) {
102 if (oceos_mutex_wait(m_0) != SUCCESSFUL) {
103 printf("Error from low priority task getting mutex\n");
104 } else {
105 printf("Low priority task got mutex\n");
106 }
107 oceos_task_start(t_0, ptr); // Start higher priority task
108
109 if (oceos_mutex_signal(m_0) != SUCCESSFUL) {
110 printf("Error from low priority task releasing mutex\n");
111 } else {
112 printf("Low priority task released mutex\n");
113 }
114 return;
115 } // fun1()
Tutorial 3 – Using Semaphores
Semaphores can be used to synchronise task actions as in this exercise.
- Three tasks this time, one high priority and the other two with the same lower priority
- Two counting semaphores, one initially 0, one initially 4, called ‘items’ and ‘spaces’
- First task starts second and third tasks
- Second task loops
- wait_restart spaces
- signal items
- Output ‘item done’ message
- Third task loops
- wait_restart items
- Output ‘got item’ message
- signal spaces
For code example see below:
1 /*
2 *********************************************************************************************************
3 * OCEOS
4 * Real-Time Operating System
5 * for
6 * ARM Microcontroller
7 *
8 * Example implementation of OCEOS
9 *
10 *
11 * (c) Copyright 2021, O.C.E. Technology
12 * All Rights Reserved
13 *
14 *
15 * Author: jfk
16 ********************************************************************************************************
17 */
18 #include <stdio.h>
19 #include <stdlib.h>
20
21 /* N.B. Application header is included first */
22 #include "oceos_config.h" // OCEOS header for this application
23 #include "tut3.h" // application header
24 #include "semaphore.h"
25
26 int main(void) {
27 int status;
28 /*
29 * Initialise the application configuration and OCEOS
30 *
31 * This application function creates the application configuration
32 * and passes it to oceos_init(), which initialises the fixed data
33 * and enables the system log
34 */
35 if (!application_init()) {
36 //LOG
37 return -1;
38 }
39 // Create Main task to
40 if (oceos_task_create(t_0,// taskID, used as index, must be in range 0 to 254
41 10, // priority, must be in range 1 to 254, lower value is higher priority
42 10, // threshold, must be in range 1 to task priority
43 1, // jobs_max, must be in range 1 to 15
44 0,// FALSE -> floating point hardware not used by task
45 1, // FALSE -> task initially not enabled
46 fun0, // main body of task
47 nullFun, // task end function
48 0,// time_deadline, must finish no later than this after start, 0 => ignore
49 0 // minimum time expected between start requests, 0 => no restriction
50 ) != SUCCESSFUL)
51 return 1;
52
53 if (oceos_task_create(t_1, 100, 100, 1, 0, 1, fun1, nullFun, 0, 0)
54 != SUCCESSFUL)
55 return 2;
56
57 if (oceos_task_create(t_2, 100, 100, 1, 0, 1, fun2, nullFun, 0, 0)
58 != SUCCESSFUL)
59 return 3;
60
61 if (oceos_sem_create(items, 10, 0, 2, FALSE) != SUCCESSFUL)// items semaphore with max permits of 10, initial permits of 0, max jobs 2
62 return 4;
63
64 if (oceos_sem_create(spaces, 10, 4, 2, FALSE) != SUCCESSFUL) // spaces semaphore with max permits of 10, initial permits of 4, max jobs 2
65 return 4;
66 /*
67 * Finish initialising OCEOS and setting up the fixed data
68 */
69 status = oceos_init_finish();
70 if (SUCCESSFUL != status) {
71 return 6;
72 } // if
73 /*
74 * Start OCEOS scheduling
75 *
76 * The OCEOS fixed data provides all the information required.
77 *
78 * If a valid task is specified, it is started and passed the pointer.
79 * Otherwise the system is put in sleep mode
80 */
81 status = oceos_start(fixed_data, t_0, (void*) nullPtr); // Start OCEOS with task to start other tasks
82 return status;
83 } // main
84
85 /*
86 * Application code functions, functions declared in asw.h
87 */
88 void fun0(void *ptr) {
89 oceos_task_start(t_1, ptr); // Start consumer task
90 oceos_task_start(t_2, ptr); // Start consumer task
91 } // fun0()
92
93 void fun1(void *ptr) {
94 while (1) { // loop forever
95 if (oceos_sem_wait_restart(items) != SUCCESSFUL) {
96 printf("Error from task t_0 task waiting items\n");
97 }
98 printf("Got item\n");
99 if (oceos_sem_signal(spaces) != SUCCESSFUL) {
100 printf("Error from task t_0 signalling spaces\n");
101 }
102 }
103 } // fun0()
104
105 void fun2(void *ptr) {
106 while (1) { // loop forever
107 if (oceos_sem_wait_restart(spaces) != SUCCESSFUL) {
108 printf("Error from task t_1 task waiting spaces\n");
109 }
110 if (oceos_sem_signal(items) != SUCCESSFUL) {
111 printf("Error from task t_1 signalling items\n");
112 } else {
113 printf("Item done\n");
114 }
115 }
116 return;
117 } // fun1()
Tutorial 4 – Timer interrupt starts task
This exercise introduces the use of timer interrupts.
- Create one task
- Set a timer to interrupt every 2 seconds
- Set timer handler to start task
- Task outputs message, then exits
For code example see below:
1 /*
2 *********************************************************************************************************
3 * OCEOS
4 * Real-Time Operating System
5 * for
6 * ARM Microcontroller
7 *
8 * Example implementation of OCEOS
9 *
10 *
11 * (c) Copyright 2021, O.C.E. Technology
12 * All Rights Reserved
13 *
14 *
15 * Author: jfk
16 ********************************************************************************************************
17 */
18 #include <stdio.h>
19 #include <stdlib.h>
20
21 /* N.B. Application header is included first */
22 #include "oceos_config.h" // OCEOS header for this application
23 #include "tut4.h" // application header
24
25 volatile U32_t count_task_start = 0;
26
27 int main(void) {
28 int status;
29 /*
30 * Initialise the application configuration and OCEOS
31 *
32 * This application function creates the application configuration
33 * and passes it to oceos_init(), which initialises the fixed data
34 * and enables the system log
35 */
36 if (!application_init()) {
37 //LOG
38 return -1;
39 }
40 // Create Main task to
41 if (oceos_task_create(t_0,// taskID, used as index, must be in range 0 to 254
42 10, // priority, must be in range 1 to 254, lower value is higher priority
43 10, // threshold, must be in range 1 to task priority
44 1, // jobs_max, must be in range 1 to 15
45 0,// FALSE -> floating point hardware not used by task
46 1, // FALSE -> task initially not enabled
47 fun0, // main body of task
48 NULL, // task end function
49 0,// time_deadline, must finish no later than this after start, 0 => ignore
50 0 // minimum time expected between start requests, 0 => no restriction
51 ) != SUCCESSFUL)
52 return 1;
53
54 if (oceos_task_create(t_1, 100, 100, 1, 0, 1, fun1, NULL, 0, 0)
55 != SUCCESSFUL)
56 return 2;
57 /*
58 * Finish initialising OCEOS and setting up the fixed data
59 */
60 status = oceos_init_finish();
61 if (SUCCESSFUL != status) {
62 return 3;
63 } // if
64 /*
65 * Start OCEOS scheduling
66 *
67 * The OCEOS fixed data provides all the information required.
68 *
69 * If a valid task is specified, it is started and passed the pointer.
70 * Otherwise the system is put in sleep mode
71 */
72 status = oceos_start(fixed_data, t_0, NULL); // Start OCEOS
73 return status;
74 } // main
75
76 /*
77 * Task 0 starting point
78 */
79 void fun0(void *ptr) {
80 timer_setup();
81 } // fun0()
82 /**
83 * Task 1 starting point;
84 * Triggered from Timer IRQ handler
85 */
86 void fun1(void *ptr) {
87 printf("Task started : %u times \n", count_task_start);
88 count_task_start++;
89 } // fun1()