Introduction to pic programming

1. Introduction to pic programming By : SherifHarhash

2. Contents • 1- what are micro controllers ? • 2-how to use them ? • 3- MC main criteria (I/O ports , timers , interrupts). • 4- C-programming ( Mikro C pro for PIC). • 5- Examples . • 6- Questions .

3. what are micro controllers ? • Micro-controllers are the most generic device used in many applications . • Simply its an IC that can perform any wanted function-( according to its features) -.

4. what are micro controllers ? • A microcontroller has a processor and many peripherals integrated with it on the same chip, like a flash memory, RAM, I/O ports, serial communication ports, ADC …Etc.

5. what are micro controllers ? • A timer module to allow the MCU to perform tasks for certain time periods. • A serial I/O port to allow data to flow between the MCU and other devices such as a PC or another MCU. • An ADC to allow the MCU to accept analog inputs for processing.

6. PIC Micro-controllers

7. OSCILLATORS • Crystal oscillator: • A crystal or ceramic resonator is connected to the OSC1 and OSC2 pins to establish oscillation. • Used for high precession timing requirements. • The capacitors are chosen according to the frequency and the preferred values in the datasheet of the used device.

8. OSILLATOR SELECT • T0CS_bit: Clock Source Select bit • 1 = Transition on T0CKI pin • 0 = Internal instruction cycle clock (CLKO) • T0SE_bit: Source Edge Select bit • 1 = Increment on high-to-low transition on T0CKI pin • 0 = Increment on low-to-high transition on T0CKI pin

9. C PROGRAMMINGLANGUAGE

10. OPERATORS • + addition • -subtraction • * multiplication • / division • % modulus • a*=b is the same as a=a*b • a/=b a=a/b • a+=b a=a+b • a-=b a=a-b • a%=b a=a%b • a<<=b a=a<<b • a>>=b a=a>>b • a&=b a=a&b • a|=b a=a|b • a^=b a=a^b

11. OPERATORS • Relational operators: • >,<,<=,>=,==,!= • Logical operators: • &&,||,! • Bitwise operators: • &, |, ^ (XOR), <<,>>,~ • Precedence: • 1.Casting • 2.Parentheses • 3.Negative • 4.Multiplication and division • 5.Addition and subtraction

12. CONDITIONALSTATEMENTS • If statement: • if (expression) • { • statement(s); • } • If-else statement: • if (expression1) • { • statement(s) • } • else if(expression2) • { • statement(s) • } • else • { • statement(s) • }

13. FOR LOOP • for( initialization ; conditional_test; increment ) • Example : • void main(void) • { • Int i; • for(i=0; i<10; i++) • printf(“%d “,i); • printf(“done”); • }

14. ARRAYS • type array_name[size] = {value list}; • Ex. • inti[5] = {1,2,3,4,5}; • Multidimensional arrays: • intnum[3][3]={ 1,2,3, • 4,5,6, • 7,8,9};FUNCTIONS

15. Functions • main() is the first function called when the program is executed. The other functions, function1() and function2(), can be called by any function in the program. • main() • { • Function1 • } • function1(inta,intb ) • { • Return() • } • function2() • { • }

16. BREAK 10 mins. only break 

17. I/O PORTS • Reading a port: • Means reading the status (voltage level) present on the pin. • Writing to a port: • Means writing to the port latches. • You have to determine the direction of the I/O pin before using it, this is done by changing the value of the TRIS register.

18. I/O PORTS • The I/O pin direction is controlled by a register called TRIS. PORT<x> is controlled by the register TRIS<x>. • If you write ‘1’ in a bit in TRIS<x> register, this means that the corresponding bit in PORT<x> is input. • A ‘0’ means -> output.

19. I/O PORTS • HOW to state data direction ? • TRIS A=0b 011001011 -> set pins (0 ,3,4,6) as o/p set pins (1,2,5,7) as i/p “ IN PORT A “ • PORT A=1; -> perform 1 as o/p for all port A pins • PORT A.f0=1; -> perform 1 as o/p for pin(0) in port A

20. SWITCHES • We use switches to give an order to the MCU to do something by changing the voltage level applied on an I/O pin (input).

21. SWITCHES • 1-Using RC circuit: • -We use it as a LPF, as the ripples • happen very fast (high frequency). • 2-By software: • By reading the value of the pin more than one time in small time intervals to make sure of the real value on the pin. • This done by testing the value, wait for some time (1~10 ms) and test again if the value is the same, so it’s the true value

22. EXAMPLE 1 • Write a program outputs high on RC0, if RB0 is low using switches and leds.

23. INTERRUPT • Definition: • An interrupt is an asynchronous signalindicate for an eventwhich needs processor’s attention immediately regardless to the instruction it executes at this moment. • It’s like a Doorbell.

24. INTERRUPTDEFINITIONS • Interrupt Flag (IF): • A bit that is automatically set if the interrupt source (event) happens. • Global Interrupt Enable (GIE): • Enables (if set) all un-masked interrupts (interrupts with IE=1) or disables (if cleared) all interrupts. • Interrupt Enable (IE): • If the GIE was ‘1’, this bit forces the CPU to respond to the interrupt signal when IF=1 when the waited event happens.

25. INTERRUPTDEFINITIONS • When the event (interrupt source) happens, the following steps happen: • 1-The corresponding interrupt flag (IF) will equal ‘1’. • 2-If the interrupt enable (IE)was ‘1’, and the global interrupt enable (GIE)was ‘1’ also, the GIE is cleared by hardware to disable any further interrupt to avoid responding to further interrupts. • 3-The return address is pushed into the stack and the PC is loaded with 0004h (the interrupt vector.