Embedded system development and labs for ARM (R. Muresan, 2005)

Embedded Systems Development and Labs; The English Edition

signaled, this task makes a state transition and some actions based on the state change. For example, when the state is changed from CLEAR to COUNT, the msCntr is cleared to restart the millisecond counter in the time update taks. When the CLEAR mode is entered, the display must be cleared one time at the transition so it is done by this task. Notice that the buffer must be written to twice to clear old buffer contents.

(5)DispTimeTsk(). This display task displays the current elapsed time by waiting for a value to be written to the display ring buffer. It then uses BufRead() to copy the time value stored in the ring buffer into a local display buffer. By using the ring buffer technique, the other tasks will not be blocked to wait for the display.

7.3.3Stopwatch Implementation Code

Open the Workspace for the project ucos_44b0_200.ews found in the …\Samsung\ucos_ii directory. Study and understand the stopwatch implementation presented in this section. Specifically, understand the main.c file. The main() function and all of the required task functions used in the start-stop watch implementation are found in this file.

main.c file

//task stack size #ifdef SEMIHOSTED

#define TASK_STACK_SIZE (64+SEMIHOSTED_STACK_NEEDS) #else

#define TASK_STACK_SIZE 10*1024 #endif

//Task definition

/* allocate memory for tasks' stacks */ #define STACKSIZE 128

/* Global Variable */

unsigned int Stack1[STACKSIZE]; unsigned int Stack2[STACKSIZE]; unsigned int Stack3[STACKSIZE]; unsigned int Stack4[STACKSIZE]; unsigned int StackMain[STACKSIZE];

void Task1(void *Id)

{

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/* print task's id */ OSSemPend(UART_sem, 0, &err);

uHALr_printf(" Task%c Called.\n", *(char *)Id); OSSemPost(UART_sem);

while(1)

{

led1_on(); led2_off(); OSTimeDly(800); led1_off(); led2_on(); OSTimeDly(800);

}

}

void Task4(void *Id)

{

int i;

INT32U NowTime;

/* print task's id */ OSSemPend(UART_sem, 0, &err);

uHALr_printf(" Task%c Called.\n", *(char *)Id); OSSemPost(UART_sem);

while(1)

{

for(i=0; i<16; i++)

{

OSSemPend(UART_sem, 0, &err); NowTime=OSTimeGet(); //»ñȡʱ¼ä //uHALr_printf("Run Times at:%d\r", NowTime); OSSemPost(UART_sem);

OSTimeDly(180);

}

}

}

void Task3 (void *Id)

{

char *Msg; int i=0;

/* print task's id */

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OSSemPend(UART_sem, 0, &err); uHALr_printf(" Task%c Called.\n", *(char *)Id); OSSemPost(UART_sem);

while(1)

{

OSTimeDly(900);

OSSemPend(UART_sem, 0, &err); EV40_rtc_Disp(); OSSemPost(UART_sem);

}

}

void Task2 (void *Id)

{

int value; char *Msg;

/* print task's id */ OSSemPend(UART_sem, 0, &err);

uHALr_printf(" Task%c Called.\n\n", *(char *)Id); OSSemPost(UART_sem);

while(1)

{

value = key_read();

// display in 8-segment LED if(value > -1)

{

Digit_Led_Symbol(value); OSTimeDly(90);

}

OSTimeDly(90);

}

}

void TaskStart (void *i)

{

char Id1 = '1'; char Id2 = '2'; char Id3 = '3';

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char Id4 = '4';

/*

*create the first Semaphore in the pipeline with 1

*to get the task started.

*/

UART_sem = OSSemCreate(1);

/*

*create the tasks in uC/OS and assign decreasing

*priority to them

*/

OSTaskCreate(Task1, (void *)&Id1, &Stack1[STACKSIZE - 1], 2); OSTaskCreate(Task2, (void *)&Id2, &Stack2[STACKSIZE - 1], 3); OSTaskCreate(Task3, (void *)&Id3, &Stack3[STACKSIZE - 1], 4); OSTaskCreate(Task4, (void *)&Id4, &Stack4[STACKSIZE - 1], 5);

ARMTargetStart(); // Delete current task

OSTaskDel(OS_PRIO_SELF);

}

void Main(void)//int argc, char **argv

{

char Id0 = '4'; ARMTargetInit();

/* needed by uC/OS */ OSInit();

OSTimeSet(0);

/* create the start task */

OSTaskCreate(TaskStart,(void *)0, &StackMain[STACKSIZE - 1], 0);

/* start the operating system */ OSStart();

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}

7.3.4 Lab Exercise

Using the examples presented so far in this chapter implement an intruder alarm application using the uC/OS-II kernel. The following describes the intruder alarm application.

Intruder Alarm Description

An intruder alarm system receives information about the state of the monitored building from a number of sensors located at every possible entrance and exit. Sensors function basically as switches, indicating whether a given sensor has detected an intruder or not. The alarm is located inside the building. It is set (armed) and reset (disarmed) from inside the building. A digital code of fixed length is required for both setting and resetting the alarm. One of the entrances, which also functions as an exit, is nominated as the entrance and the exit after the alarm has been set.

Timing information is crucial for proper functioning of an intruder alarm. When the alarm is initially set, a specific time delay is allowed for the user to leave the building through the nominated exit. When the alarm is set, the use of any of the entrances other than the nominated one for re-entry activates the alarm instantly or, at most, within a matter of a few seconds. The sensors monitoring the entrance nominated for re-entry and the route to the alarm control point do not activate the alarm until a set time has elapsed. This set time allows the user to enter the building and disarm the alarm by entering the correct digital code. If this is not done successfully, the alarm is activated at the end of the set time.

The alarm system has a siren and a strobe and these are located outside the building. If an intruder is detected or the alarm is not disarmed by the person entering the building through the nominated entrance during the required time, the siren begins to sound and the strobe begins to flash immediately, as mentioned above. In this event, the siren continues to sound for a specified time, usually for a few minutes, and then stops, but the strobe continues to flash. The alarm can be reset by the user only by entering the correct code. If the alarm has already been triggered, this would turn the alarm off. The correct code is the most up to date code entered when arming the system.

When entering the code for disarming the alarm, the user is allowed a maximum period to complete the task. If the user fails to complete this within the given time, the system discards the partial entry and awaits for the next attempt. The user is allowed as many attempts as possible to enter the correct code within the allocated time. If the alarm has already been set off, after this period it cannot be reset except by an appointed independent authority.

Some reasonable limiting values for the timing parameters involved are:

a.Time allowed for setting the alarm and leaving the building – 30 seconds

b.Time between detecting an intruder and triggering the alarm off – 5 seconds

c.Time allowed for re-entry through the nominated entrance and start resetting the alarm – 2 minutes

d.Duration for resetting the alarm after re-entry – 1 minute

e.Maximum duration for entering the code at each attempt – 20 seconds

f.Duration of the siren sound – 5 minutes

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NOTE: In this application you can use the keypad in order to simulate the entrance and exit switches; the 8-SEG LED or the LCD to perform the flashing; the earphone to simulate the siren sound.

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Appendix A: ARM Instruction, ARM Addressing and Thumb Instruction

Quick Reference

Table A-1 ARM Instruction Quick Reference

Table A-2 ARM Addressing Quick Reference

Table A-3 Thumb Instruction Quick Reference

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Appendix B: ARM and Thumb Instruction Code

Table B-1 ARM Instruction Set Code

Table B-2 Multiplex and Other Read/Write Memory Instructions Table B-3 Other Instructions

Table B-4 Thumb Instruction Set Code

Figure B-1 Thumb Instruction Set Code

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Appendix C: Embest ARM Related Products

1.Embest IDE

2.Flash Programmer

3.ARM JTAG Emulator

(1)Embest Easy ICE for ARM

(2)Embest Emulator for ARM

(3)Embest PowerICE for ARM

Figure C-1 Standard Emulator Figure C-2 Enhanced Emulator

4.ARM Development Boards

(1)Embest S3CEV40 Full Function Development Board

Figure C-3

(2)Embest AT91EB40X Development Board

Figure C-4

(3) AT91EB55 Development Board

Figure C-5

(4) AT91EB63 Development Board

Figure C-6

(5) NET-START! Development Board

Figure C-7

(6) ML674000 Development Board

Figure C-8

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Appendix D: Content of CD-ROM

1.Content of CD-ROM

2.CD-ROM directory architecture

3.Usage of CD-ROM

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