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
Fri Dec 12 2014, 04:38 AM
@Abdul BAsit, Post in forum please. We will help you.
Wed Dec 10 2014, 06:41 PM
Abdul BAsit
I am working on smoke detector using AT89S52 and dont know how its wors..kindly send me circuit diagram and code for its hardware & software implementation
Tue Dec 09 2014, 11:30 AM
Irinel
Please send me the content of that cd-rom (embedded c - michael j pont. Thank you.
Tue Dec 09 2014, 02:45 AM
kmyo
please give me the operation of 12v trickle charger
Sun Dec 07 2014, 07:50 AM
hidawi
we need the circuit diagrom of the remote control of iduction motor by android appliction
PsySc0rpi0n
Tue Dec 02 2014, 10:30 AM
I have no idea... I'm new to micro controllers
Tue Dec 02 2014, 08:35 AM
samarnath dev
how can usb key bord interfasing to dot matrx led moving, by asm51 ?
Tue Dec 02 2014, 08:32 AM
samarnath dev
how can usb key bord interfasing to 8051 by asm code?
Fri Nov 28 2014, 06:31 AM
babar
aoa ,, i need a project for 8051 microcontroler can some one plz give me the pdf form of this project android control robot
Fri Nov 28 2014, 06:30 AM
babar
hi

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Comments

naimish324
Wed Dec 17 2014, 04:48 AM
sathish177
Tue Dec 16 2014, 06:43 PM
djnokey
Sat Dec 13 2014, 12:12 PM
sai9113
Tue Dec 09 2014, 07:23 AM
alexlomol
Fri Dec 05 2014, 12:06 AM
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Thu Dec 04 2014, 10:11 AM
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Mon Dec 01 2014, 01:45 PM
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Sat Nov 29 2014, 04:43 PM

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Forum Activity
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Dec 17 2014, 11:21 PM
i've tried this code but faced a syntax error on l...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Dec 17 2014, 09:53 PM
Thank you sir for help! I did change the code sir ...
sankalp_s Avatar
Posted By sankalp_s
Wed Dec 17 2014, 04:11 PM
ORG 000H ; starting address SJMP LABEL1 ORG 0...
engr1931 Avatar
Posted By engr1931
Wed Dec 17 2014, 08:09 AM
Thank you sir for help! I did change the code sir ...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Dec 16 2014, 05:05 AM
Did you check our tutorial?http://www.8051projects...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Dec 16 2014, 04:55 AM
ORG 000H ; starting address SJMP LABEL1 ORG 0...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Dec 16 2014, 04:44 AM
Well Mode 2 is only 8-bit so its even simpler, max...
software_developer Avatar
Posted By software_developer
Sat Dec 13 2014, 08:05 AM
Hello Sir,I want to access one file from SD card u...
sankalp_s Avatar
Posted By sankalp_s
Fri Dec 12 2014, 06:29 PM
Thank u sir for your response. sir can u explain m...
PsySc0rpi0n Avatar
Posted By PsySc0rpi0n
Fri Dec 12 2014, 04:37 PM
Does that method of reading timers works if I use ...