ADC read error when data is receieved from RS232 wiht GETS()

[hamham]

Dear Sir,
This program is received a data from PC (pc sent 3 chr int and there are an ascii13 chr end of this data)
ADC read a value (10 bit) and sent it to pc
this sytem work perfect when without received data; when I start to chrs from pc, ADC value start to incorrect sometimes (if adc is 8bit inccorrect value 0, if adc is 10 bit incorrect value 768,
I mean when I start pic,
I see a value on pc
for example
(adc 8 bit and potantiometer half is connected A0)
89
89
87
87
89
88
all value is correct
when I start to data from pc to Pic
data is Pc screen;
87
88
89
87
88
89
0 // (error)
87
88
0 //(error)
88
0 // (error)

What is the reason of this error?



#include <18F452.h>
#use delay (clock=40000000)
#include <stdio.h>
#include <stdlib.h>
#include <lcd.c>
#include <math.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use rs232(baud=57600, xmit=PIN_C6,rcv=PIN_C7,stream=PC)


int32 timersondeger=0,CARPIM=0;
int32 xxx=0,sayici,sayici2=0;
short kontrol=0;
char acich[3];
int16 throttle=0,aci=450,devir=0,sondeg=0,kalan=0,tam=0,thhata;
int8 i=0,k=0,x=0,mn;





#INT_RDA
void rs232()
{

gets(acich);

}



void setup()
{
set_tris_a(0b001111);
setup_adc_ports(RA0_RA1_ANALOG_RA3_REF);
setup_adc(ADC_CLOCK_INTERNAL );

set_adc_channel(0);

setup_psp(PSP_DISABLED);
setup_spi(FALSE);
ext_int_edge( 0, L_TO_H);
ext_int_edge( 1, L_TO_H);
enable_interrupts(global);
enable_interrupts(int_rda);
lcd_init();

}

void main()
{
setup();

while(true)
{

lcd_putc("\f") ;
lcd_putc("aci:"); printf(LCD_PUTC, "%ld",aci);
lcd_putc("\n");
lcd_putc("kel:"); printf(LCD_PUTC, "%lU",throttle);
lcd_putc(" d:"); printf(LCD_PUTC, "%lu",devir);
aci=atol(acich);

delay_ms(1);
thhata=throttle;
throttle=Read_ADC();

throttle++;


printf("%4lud",devir);
aci=atol(acich);
printf("%04luy",throttle);




}
}

[Ttelmah]

First, don't use gets, in an interrupt handler.
When the interrupt is called, potentially just _one_ character is waiting. gets, waits for an entire string (up to the terminating character, and using 'gets', means everthing in the main, will be stopped till the whole string arrives. Just get one character in the interrupt, and have your own code to build the string and terminate it.
Second comment, be careful about lengths. You only allow three characters of storage for your input string. String storage must be enough to hold the terminating character, as well as the string itself. I'd guess that sometimes this string is overrunning, and destroying data held afterwards. When you write your own input function, make it stop when the buffer is full...
Learn to use the code buttons.
Why do you have two setups forexternal interrupts that are not used?.

Best Wishes

[ckielstra]

[hamham]

[HAMHAM]

[Ttelmah]

The internal oscillator, is not rated to work beyond 25MHz. To work at 40MHz, requires you to either use a 10MHz crystal, and HSPLL fuse, or feed an external clock at 40Mhz into the chip, and select EC, or EC_IO, which are designed to accept such an input.

Best Wishes

[Guest]

[Guest]

[ckielstra]

Please, when posting code use the 'code' button. This will help to preserve the formatting and makes for easier reading.

What does your clock circuit look like? Is it a crystal or a clock generator? EC_IO is only to be used with a clock driver circuit, not with a crystal.

[Guest]

[ckielstra]