Time delay in PIC16f876-A

[amitdandyan]

pic16f876

I have developed the following program to glow an led connected to first pin of PORT B using Mikro C...now the problem is how can i give delay value, eg 250us etc...????


unsigned short i;

void main()
{
TRISB = 0;
PORTB = 0X00;
USART_init(9600); // initialize USART module
// (8 bit, 19200 baud rate, no parity bit...)
while (1)
{
if (USART_Data_Ready()) // if data is received
{
i = USART_Read(); // read the received data
USART_Write(i); // send data via USART
PORTB = 0x01;
Delay_ms('i');
PORTB = 0x00;
}
}
}

 

[Tajinder Singh]

pic16f876 timer

u have done this much that means u know programming, its a very simple thing

either use a simple for loop delay
or use timer

 

[amitdandyan]

pic16f876 delay

Thanx Sir, but what i want to ask is that how can i physically give a value for 'i' eg. 250 or 100 etc. For example, i connect a LED to port B and i want to change the time of glow of that LED...So i need to give different values of 'i'....how can i give these values using Keyboard ????

If you have used Mikro C, then please let me know how to use its USART terminal for Communication....

Waiting for your reply........

 

[gilbertomaldito]

72 hour time delay modules

I would like to clarify your questions. Are you asking how to compute for the Constant OFF time of the clock... ?

 

[Kurenai_ryu]

delay_ms(x)

Delay_ms('i'); ???????

maybe Delay_ms(i);

or maybe declare it???

void main(void){
int i;
...

i=250;
...
Delay_ms(i);
...


or just Delay_ms(250);

maybe mikroC has something like Delay_us(250); for microseconds??? (Delay_ms should be in miliseconds)

 

[the lion]

usart_init() usart_write()

char y;
int x;
void main()
{trisa=0;porta=0;


usart_init(9600);
for(;
{if(usart_data_ready())
{y = USART_Read();
usart_write;
PORTa.f0= 1;
x=y-48;
x=x*1000;
vdelay_ms(x);
porta.f0=0;

}
}
}

this code will work
but the output is porta.f0
and the time will be variable
from
1 to 9 sec

you can change x=x*1000 to
x=x*10000;
and the time will be variable
from
10 to 90 sec

 

[amitdandyan]

baut rate 9600 pic 16f876

thanx loin....bt i have one question...why we cann't use Delay_ms() instead of vdelay_ms(x)?????

 

[the lion]

delay pic16f876a c

because that delay_ms(); is used only with
a constant value but vdelay_ms(); can be used
with variables
but you can use delay_ms();to have a variable delay
but not in a direct way

 

[amitdandyan]

timer pic16f876

thanx man.....plz also explain the indirect way to use delay_ms(x);

 

[the lion]

usart_read

char y;
int x,n;
void main()
{trisa=0;porta=0;


usart_init(9600);
for(;
{if(usart_data_ready())
{y = USART_Read();
usart_write;
PORTa.f0= 1;
x=y-48;

for(n=0;n<x;n++)
{delay_ms(1000);}
porta.f0=0;

}
}
}
this code shows how you can use delay_ms();
to make a variable delay

regards

 

[Faizan Jawaid]

pic16f876 a

I once had the same problem before I used a good compiler which has a built-in delay function ( delay_ms(x) )

use a program like this

while(1)
{
for(a=0;a<255;a++) // int a;
for(b=0;b<255;b++); // int b;
LED=1; // Just to check the logic
for(a=0;a<255;a++)
for(b=0;b<255;b++);
LED=0;
}

Its simply a nested loop to waste the clock cycles

Use a simulator like Proteus ISIS and put a oscilloscope on the LED pin..and measure the time. In this way you can find out the time period of the loop

NOTE: this will not produce same delay for any crystal oscillator. Its just to check how much the delay is for the specific crystal osc and the loop variable

 

[amitdandyan]

delay in c for pic16f876

@the loin....

char y;
int x;
void main()
{trisb=0;
portb=0;
usart_init(9600);
for(;
{if(usart_data_ready())
{y = USART_Read();
usart_write;
PORTb.f0= 1;
x=y-48;
vdelay_ms(x);
portb.f0=0;

}
}
}

i hv burned this code in PIC16F876-A and it is working fine to give a delay from 1ms to 5ms.....but for higher values it fails to give an exact delay....!!!!!!!!!!!!