I need help with code which reads characters from rs232?

[Masa]

Hi, sorry my bad english

I try to do program which send string to computer e.g( "$52"). When computer get string, it send back some information e.g( -12.4C). My problem is that I can't read that data and put it right format. I have tested interface and that is okay. Only problem is code.

Psuedo code:

char result[10];
int i=0;

printf("$52"): // send string to computer

while( !kbhit() ); // waits computer

while( kbhit){ //try to write data to 'result'

result[i]=getch();
i++;
}


What goes wrong?

[asmallri]

the pseudo code looks ok. You have not decribed the problem enough to be able to determine the possible problem. Can you post an example of your program the demonstrates the problem including the fuse statements, #use statements and which processor you are using.
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[Masa]

Yes,

prosessor is pic16f877

clock=12MHz

I test different baudrates, 1200,2400,9600 but problem not solved. I just wondering is this loop too slow to read characters:

while( kbhit){ //try to write data to 'result'

result[i]=getch();
i++;
}

printf(result)

because, when I test code with terminal program, first I can see $52, that is okay and terminal wait until I send packet. My test packet was 1234. But now I can read only 12 on terminal.

[asmallri]

you have not posted enough code to see where the problem is. For example, I cannot tell if you are using the harware UART or the Software UART function.

Instead of the loop being too slow, it could be too fast. For example, if the #use RS232 statement is enabling the hardware UART then the program could service getch() so fast that after reading in the second character kbhit() returns false because the third character is still being serialised into the UART. When this happens you will drop out of the while loop. Another problem is that you code does not write a 0 at the end of the string in result. The printf statement could end up printing garbage.
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[Ttelmah]

[Masa]

I wrote new code, because old one was so long.

from headerfile:
#include <16F877A.h>
#device adc=8
#use delay(clock=12000000)
#fuses HS,NOWDT


real code:

#include "D:\\test_rcv.h"
#use rs232(baud=1200, xmit=PIN_c6, rcv=PIN_c7)

char result[10];

void main() {
int i=0;
setup_adc_ports(ANALOG_RA3_RA2_REF);
setup_adc(ADC_CLOCK_DIV_32);
setup_psp(PSP_DISABLED);
setup_spi(FALSE);
//setup_counters(RTCC_INTERNAL,RTCC_DIV_2);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
SET_TRIS_D(0);
set_tris_b(0b11111101);
set_tris_c(0b10000000);
disable_interrupts(global);

while(1){

printf("$52");
while( !kbhit() ); // wait until computers send 1. character

while( kbhit() ){

result[i]=getc();
i++;
}

printf(result);
}
}

Terminal:
:$52
TX-->example<nul>
:exa$52exa$52
TX-->example<nul>
:

After that the prosessor do nothing, and terminal neither. I try to use get_string() from input.c, but that wasn't fix problem. Should I use interrupts?

[Humberto]

Masa wrote:

[C#R# []]

Hi.. at short time ago, I wrote a code with RS232 and work very weel.. but at begining I had some problems...well...the problem is the watchdog.
The new getc() ( that´s I named getcW() ) stoped the problem..


int getcW ()
{
while ( !(*PIR1 & 0b00100000)) restart_wdt() ;
return (*RCREG);
}

// WATCH DOG... YOU ARE SO BAD...HEHEHE !!!!

humm...that´s good for me ..and I would like to be good for you too....
don´t forget :

#define PIR1 0x0C
#define RCREG 0x1A // for PIC16F871 !!!

[Mark]