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RS232 weird behaviour

 
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foxOnTheRun



Joined: 17 Apr 2010
Posts: 43

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RS232 weird behaviour
PostPosted: Thu May 20, 2010 4:54 am     Reply with quote
I'm using a 16F688 with it's built in uart:

Code:
#use rs232(uart1,baud=9600,stream=sdcard,PARITY=N,BITS=8,STOP=1)

I've wired it to a openLog module from sp***fun (not sure if i can write full name, so..) which has an uart too; both are working with logic level so 0..5V.

Also, using a max232 I've linked the pc to the serial line, so I can monitor what's going on (using putty).

At power up the program only execute 2 simple instructions:

Code:
fputc(0x0D,sdcard);

This is an ENTER, I've seen some garbage already appearing on the line, so I force them out by forcing the other board to try to process it.

Code:
fprintf(sdcard,"Hello world\r");

This is where things get interesting, monitoring the line, on the terminal (I use putty) I only capture "ello world", the first char is missing..

Again, if I send:

Code:
fprintf(sdcard,"new test.txt\r");


Which is a valid command for the serial board, I get as reply "ew test.txt unknown command".. so actualy the system is eating the first char - gosh!

The PIC and the board are directly connected, TX and RX pins are inverserly matched - are there some extra settings or issue to take care of when setting up a serial link?

This is the full main.c as reference (yes, there is a LCD16x2 connected to the PIC).
Code:

#include main.h"
#include LCD.C>
#include <string.h>
#include <stdlib.h>
#include <limits.h>

#define LED PIN_A0

char str[80]="";
int i=0;
int n=0;
int f=0;
int log=0;

#use delay(clock=8000000)
#int_RDA
void  RDA_isr(void)
{
   str[i]=getch(sdcard);
   i++;
   if (i>79) i=0;
}

#use delay(clock=8000000)
void main()
{
   setup_adc_ports(NO_ANALOGS|VSS_VDD);
   setup_adc(ADC_OFF);
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
   setup_timer_1(T1_DISABLED);
   setup_comparator(NC_NC_NC_NC);
   setup_vref(FALSE);
   
   enable_interrupts(INT_RDA);
   enable_interrupts(GLOBAL);
   setup_oscillator(OSC_8MHZ);
     
   output_low(LED);
   output_high(LED);
   
   lcd_init();
   printf(lcd_putc,"\fCard INIT 3s..");
   delay_ms(3000);
   output_low(LED);
   printf(lcd_putc,"\fLogging..");
   
   fputc(INVIO,sdcard);
   
   fprintf(sdcard,"Hello world\r");
   
   while(1);
}

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Wayne_



Joined: 10 Oct 2007
Posts: 681

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PostPosted: Thu May 20, 2010 7:13 am     Reply with quote
What is INVIO ?
foxOnTheRun



Joined: 17 Apr 2010
Posts: 43

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PostPosted: Fri May 21, 2010 2:55 am     Reply with quote
Oh, I forgot, it's a define for ENTER = 0x0d.
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languer



Joined: 09 Jan 2004
Posts: 144
Location: USA

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PostPosted: Mon May 24, 2010 1:16 am     Reply with quote
What are your "#use rs232" and "setup_uart" (if used) definitions?
Wayne_



Joined: 10 Oct 2007
Posts: 681

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PostPosted: Mon May 24, 2010 3:30 am     Reply with quote
I assume you have
PIC TX -> Module RX & PC RX
PIC RX <- Module TX (only ?)

What do you get on the PC if you disconnect the module and just have Pic to PC ?
foxOnTheRun



Joined: 17 Apr 2010
Posts: 43

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PostPosted: Fri May 28, 2010 5:14 am     Reply with quote
languer wrote:
What are your "#use rs232" and "setup_uart" (if used) definitions?


First post, first 2 lines:

Code:
#use rs232(uart1,baud=9600,stream=sdcard,PARITY=N,BITS=8,STOP=1)

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Listen, why don't you relax? Take a pill, bake a cake or go and read the encyclopedia.
foxOnTheRun



Joined: 17 Apr 2010
Posts: 43

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PostPosted: Fri May 28, 2010 5:18 am     Reply with quote
I found something:

if I send: 0x0d (return) to confirm the data/commands the system was behaving wrongfully.

If I send printf("text-or-commands\n\r") the system was back in operation as it should.

So, I can consider the question closed, the "fault" looks like is on the receiver side.

The PIC connected to the PC was behaving perfectly fine. :)
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