Can't receive '\0' null character in serial(rs232)

[isv10]

Hello. My project with pic16f1829.
Receiving string with int_rda but can't detect null \0 char.
Someone has a comment ?



#define BUFFER_SIZE 32
int1 have_string=FALSE;
char string[BUFFER_SIZE];
int index=1;



#int_rda
void serial_isr() {
char c;
c=getc();

if(c=='\0')
{
have_string=true;
string[index]=c;
return;
}
string[index]=c;
if(index >= BUFFER_SIZE)
index=index-1;
else
index++;
printf("H");
}





void main()
{
setup_wdt(WDT_1S); //~2.0 ms reset
restart_wdt();
// setup_adc_ports(sAN2|sAN4|sAN5);
// setup_adc(ADC_CLOCK_DIV_2);
//setup_timer_2(T2_DIV_BY_1,4,1); //1.0 us overflow, 1.0 us
enable_interrupts(global);
enable_interrupts(int_rda);
restart_wdt();
output_high(PIN_C7);
delay_ms(500);
output_low(PIN_C7);
delay_ms(500);
output_low(PIN_C7);
//printf("test code");
restart_wdt();

while(TRUE)
{
restart_wdt();
if(have_string)
{
puts(string);
have_string=FALSE;
}
}
}[/b]

[temtronic]

general comments..
1) no #use RS232(...options...) Pre prosessor directive. That's kinda important

2) delete all the WDT related code. NOT required

3) no #include device header. That's kinda required too !

4) use the [code] button( top center of this page) when posting code. Really helps us 'see' the code !

5) you'll need to add 'ERRORS' to the missing #Use RS232(...) options

Probably more but coffee's ready !
Jay

[isv10]

Thanks for your reply.
This code works fine but can't detect '\0' null char. When i send test string with PC and return it with puts() in int_rda it works good. But when i want to control string with the following code it can't detect '\0'.

[temtronic]

OK, now get rid of the WDT AND add 'errors' to the USE RS232.

The WDT is 'about 2ms', probably +-50-100%, so it could be tripping at 1ms...
hmm...9600 baud is 'about' 1 character per 1ms
so it is possible the WDT is resetting the PIC.

Without the 'ERRORS' option, the HW UART will lockup after the 2-3 characters. Now I don't use that PIC and don't know IF the HW UART is being used. If it is a 'software' UART, then the ISR won't work....

Jay

[isv10]

Thanks for your help. I test WDT change.

[Ttelmah]

First, learn to use the code buttons....

[isv10]

Hello Ttelmah and thanks for your help. I changed index=1 and forget to correct it. I send string from pc to micro (with serial port terminal) and then try to find '\0' from end of string. But when i send for example 3 char string, program return (HHHH) or send 5 char string it return (HHHHHH). It means i have 4 interrupt for 3 char string, and 6 interrupts for 5 char string. I want to detect end of string.

[Ttelmah]

Are you absolutely sure your program is sending the NULL?.
Terminal programs etc., normally won't. If you send a string with something like sendln, it prints the string, and then a line feed, not a NULL...
You need to find out what your source program is actually sending.
It is extremely rare for PC programs to actually print the NULL.

Put it in perspective, CCS won't either.
If you print a string with:

printf("%s", string);

The NULL won't be printed.

[isv10]

How can i find it ? I try with '\n' and no response. When i send string from terminal, for example (test) string i receive (HHHHHtest)
and for another string in new line receive...

[temtronic]

Post the name of the 'terminal program' on the PC. Should be easy to figure out how to add the null to the transmitted data...

Jay

[isv10]

Serialport Terminal
by coad.net

[isv10]

Hi. Problem was solved.

Windows is backward compatible with MS-DOS and used the CR-LF convention because MS-DOS was compatible with CP/M-80 which used the CR-LF convention because that was how you drove a printer (because printers were originally computer controlled typewriters).
The result is in Windows based terminal, send '\r\n' or '\n' end of string. Thus i use '\r' in my program and it works very good!!!!!!!!!!!!!!!!