Embedded Systems Programming. ETEE 3285 Topic HW3: Coding, Compiling, Simulating

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1 Embedded Systems Programming ETEE 3285 Topic HW3: Coding, Compiling, Simulating 1

2 Assignment Write the Chasing Lights Program in C Use Codevision AVR to compile the program and remove all syntax errors Simulate the program in AVR Studio, identify all logic errors If logic errors are found, go back to Codevision AVR and make the necessary changes 2

3 LED Sequence The leftmost LED should light (all others are off) 3

4 LED Sequence Then turn off the leftmost LED and turn on the next one to its right 4

5 LED Sequence Then shift the on LED to the right again 5

6 LED Sequence And again 6

7 LED Sequence And again 7

8 LED Sequence And again 8

9 LED Sequence And again 9

10 LED Sequence And again 10

11 LED Sequence Then start over at the leftmost LED (and continue forever) 11

12 First Program Many inexperienced C programmers will write a program as shown Assuming a 1 is on and a 0 is off void void main(void) main(void) DDRB DDRB 0xFF; 0xFF; PortB PortB is is all all outputs outputs 0x00; 0x00; turn turn off off all all the the lights lights while(1) while(1) do do forever.. forever.. 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; } } } } 12

13 First Program Many inexperienced C programmers will write a program as shown Assuming a 1 is on and a 0 is off void void main(void) main(void) DDRB DDRB 0xFF; 0xFF; PortB PortB is is all all outputs outputs 0x00; 0x00; turn turn off off all all the the lights lights while(1) while(1) do do forever.. forever.. 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; } } } } While this will work, there are better solutions This is what I call a brute force program it is inelegant. 13

14 First Program Many inexperienced C programmers will write a program as shown Assuming a 1 is on and a 0 is off void void main(void) main(void) DDRB DDRB 0xFF; 0xFF; PortB PortB is is all all outputs outputs 0x00; 0x00; turn turn off off all all the the lights lights while(1) while(1) do do forever.. forever.. 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; 0b ; } } } } While this will work, there are better solutions This is what I call a brute force program it is inelegant. Let s enter it in Codevision 14

15 Open Codevision Open Codevision. It will only look like this IF you were not working on a program the last time you used it 15

16 Open New Project Click on File -> New 16

17 Open New Project Click on Project and then OK 17

18 Use Code Wizard It is easiest to use the Code Wizard, so click yes. 18

19 Code Wizard Here you can change the chip and the clock speed 19

20 Ports You can also initialize the ports 20

21 Serial Ports, Interrupts, Timers The Code Wizard also helps you setup: External Memory Interrupts Timers Serial Ports LCDs 21

22 Done? When done, click on File -> Generate, Save, and Exit 22

23 Save Files When done, click on File -> Generate, Save, and Exit It will ask you to save 3 files it will prompt you 23

24 New File Finally, the new file will open (It doesn t take long) 24

25 Unnecessary Code But, there is a lot of unnecessary code: it initializes all the ports, interrupts, timers,etc according to the default parameters but that code is not needed for this program 25

26 Template You ll be left with a template Place global variables here Local variables here And the program statements here 26

27 Enter the Program Place the program here 27

28 Build All Save everything And the choose Build All from the Project Menu 28

29 No Errors Hopefully we ll have no errors or warnings 29

30 The Debugger So, its time to simulate Click on the ladybug This will call up AVR Studio 30

31 Open Project Choose Open 31

32 *.cof & *_cof.aps files Choose Open and then the *.cof and the _cof.aps files then click next 32

33 Simulator and ATMega128 Choose AVR simulator and the ATmega128 33

34 The AVR Simulator This setup opens because it is the way I left AVR simulator the last time I exited yours may look different. I click on I/O ATmega128 so that I can see PortB 34

35 I/O PortB still has to be opened so that we can see the rest of Portb 35

36 PortB.7 With PortB open,, DDRB, and PINB are all visible Note also that F11 has been pressed so that the instruction that sets b7 in has executed (.7 1) 36

37 PortB.6 Now

38 PortB.5 Now

39 PortB.4-1 Now.4 1 Now.3 1 Now

40 PortB.0..Glitch Now.0 1, then something happens it executes the while, and during that time.0 stays 1. 40

41 Arrays void void main(void) main(void) char char LEDs[8] LEDs[8] 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b , 0b b }; }; So a new program was tried using an array and a for loop. But there was still a delay while the while and for statements were executing. One more program was tried char char i i 0x00; 0x00; DDRB0xFF; DDRB0xFF; while while (1) (1) for for (i0; (i0; i<8; i<8; ++i) ++i) LEDs[i]; LEDs[i]; }; }; } } 41

42 Shift Operator char char leds leds 0b ; 0b ; void void main(void) main(void) DDRB DDRB 0xFF; 0xFF; PortB PortB is is all all outputs outputs 0x00; 0x00; turn turn off off all all the the lights lights This program worked very well there was no difference in timing between one bit and the next, and especially between.0 and.7 } } while(1) while(1) do do forever.. forever.. leds; leds; leds leds >> >> 1; 1; if if (leds (leds 0) 0) leds leds 128; 128; } } 42

43 Summary The Chasing Lights Program was written in C several times Brute Force Arrays Shift Operator The shift operator proved to be the best Discovered while simulating 43

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