Basic of a C program

As we already discussed, Keil C is not much different from a normal C program. If you know assembly, writing a C program is not a problem, only thing you have to keep in mind is forget your controller has general purpose registers, accumulators or whatever. But do not forget about Ports and other on chip peripherals and related registers to them.

In basic C, all programs have atleast one function which is entry point for your application that function is named as \"main\" function. Similarly in keil, we will have a main function, in which all your application specific work will be defined. Lets move further deep into the working of applications and programs.

When you run your C programs in your PC or computer, you run them as a child program or process to your Operating System so when you exit your programs (exits main function of program) you come back to operating system. Whereas in case of embedded C, you do not have any operating system running in there. So you have to make sure that your program or main file should never exit. This can be done with the help of simple while(1) or for(;;) loop as they are going to run infinitely. Following layout provides a skeleton of Basic C program.

void main()
{
	//Your one time initialization code will come here
	while(1){
		//while 1 loop
		//This loop will have all your application code
		//which will run infinitely
	}
}

When we are working on controller specific code, then we need to add header file for that controller. I am considering you have already gone through "Keil Microvision" tutorial. After project is created, add the C file to project. Now first thing you have to do is adding the header file. All you have to do is right click in editor window, it will show you correct header file for your project.

Figure below shows the windows context for adding header file to your c file.

include file

Writing Hardware specific code

In harware specific code, we use hardware peripherals like ports, timers and uart etc. Do not forget to add header file for controller you are using, otherwise you will not be able to access registers related to peripherals.
Lets write a simple code to Blink LED on Port1, Pin1.

#include <REGx51.h>
 //header file for 89C51
void main()
{
	//main function starts
	unsigned int i;
	//Initializing Port1 pin1
	P1_1 = 0; //Make Pin1 o/p
	while(1){
		//Infinite loop main application
		//comes here
		for(i=0;i<1000;i++)
			; //delay loop
		P1_1 = ~P1_1;
		//complement Port1.1
		//this will blink LED connected on Port1.1
	}
}

You can now try out more programs. "Practice makes a man perfect".

In next section of this tutorial, we will learn how to mix C and assembly codes.

Conversation

ajay_bhargav
Mon Oct 20 2014, 11:22 AM
@skrishna, please post in forum so we can help you better.
Tue Oct 14 2014, 01:45 PM
skrishna
how do i write an ALP equivalent 7segment display interfacing embedded c program (both 8051 microcontroller)
Sat Oct 11 2014, 06:41 PM
vaidehi
want details of seven segment LED display common cathode ( IC CD 4026)
Fri Oct 03 2014, 12:52 PM
Narsim
Rickey you inspired me a lot ... I am also planing like you ...
ExperimenterUK
Wed Oct 01 2014, 09:33 PM
We're back.. we had a bug, but posting is back to normal
ExperimenterUK
Sat Sep 13 2014, 04:34 PM
jaimin1212,Pimpalkhare Create a thread for your question
jaimin1212
Sat Sep 13 2014, 06:35 AM
i want to make self balancing robot using MPU6050 using atmega8.. please help to get data of gyro and accelerometer from this sensor through atmega8.
Thu Sep 11 2014, 01:00 PM
Sunil Pimpalkhare
Hello sir, I am trying to make Wearfin project https://www.youtube.com/watch?v=iZ6PVBvQf-g so can u help me in teaching how to built the program???
Thu Sep 11 2014, 06:21 AM
hariom panday
plz hlp me in my project
iec.naga
Tue Sep 09 2014, 05:19 AM
spi

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hiswe
Thu Oct 23 2014, 04:18 PM
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Sun Oct 19 2014, 01:56 PM
msideal
Thu Oct 16 2014, 08:48 AM
robotgirl
Tue Oct 14 2014, 06:23 PM
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Mon Oct 13 2014, 05:48 AM
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Mon Oct 13 2014, 02:47 AM
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Sun Oct 12 2014, 12:20 PM
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Fri Oct 10 2014, 05:15 AM

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Try holding STB high all the time.You might as wel...
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