Problem in Serial Communication using PIC

th3gr8 · Jun 20, 2014

Hello everybody ..
I am working with Serial Communication using Pic MCU .. I got a problem in that .. It is that the programs that consumes less RAM and ROM are working fine (i.e. their outputs are fine at HyperTerminal), but the outputs of the programs that consumes more RAM and ROM (even 20% of RAM and ROM) of MCU doesn't even appear at the HyperTerminal.. Also, when i press the data-lines again and again, i receive some garbage characters on the hyperterminal .. Is there something wrong with my hardware?? .. Plz help !!
I am using PIC16F877A, 4MHz crystal and PIC-CCS for programming ..
Here is the code:

Code C - [expand]
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// To Calculate Radius of Circle using RS232 Protocol
#include <16F877A.h>
#fuses HS, NOLVP, NOWDT,BROWNOUT
#use delay(clock = 4Mhz)
#use rs232(baud=9600, xmit=pin_B0, rcv=pin_B1)
 
void main()
{
unsigned int r=0,c;
float a=0;
lcd_init();
delay_ms(30);
loop:
printf("\n\rInsert value of r (from 0-9): ");
r = getc();
putc(r);
delay_ms(1000);
r = r-48;
lcd_putc('\f');
lcd_gotoxy(1,1);
//lcd_putc(r);
printf(lcd_putc,"Radius = %d", r);
a = (3.14*r*r);
printf("\n\rArea of circle = %f", a);
lcd_gotoxy(1,2);
printf(lcd_putc,"Area = %f", a);
printf("\n\rRepeat? (Y/N): ");
c = getc();
putc(c);
if(c=='y')
{
goto loop;
}
else
{
break;
}
}

betwixt · Jun 20, 2014

Try to code without using the 'goto' instruction - you will regret it later when your programs are more advanced. Also consider where the 'break' leads to in line 36.

I think your underlaying problem is that you use 'printf' and also floating point math, both are huge memory hogs and relatively slow on PICs without multiplication support. 18F devices are better, faster and have more memory for this kind of application.

If you want to make it smaller, try this:
1. make the fixed text into a const array. For example "const char *Text1 = {"Radius = "}; // this puts the text in ROM instead of RAM
2. send the characters one at a time from the array in a loop.
3. instead of using 3.14, use 314 and shift the decimal two places in the result. This lets integer math instead of floating point be used.

Brian.

Problem in Serial Communication using PIC

th3gr8

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betwixt

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th3gr8

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Problem in Serial Communication using PIC

th3gr8

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