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why I have to connect to CLKO instead of CLKI

 
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young



Joined: 24 Jun 2004
Posts: 285

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why I have to connect to CLKO instead of CLKI
PostPosted: Fri Feb 18, 2005 11:17 am     Reply with quote
I use a ECS-100A crystal 4Mhz, I connected it to 16f819 at CLKI pin, the system does not work, when I connected to CLKO pin it works, why? crystal output should go into CLKI right?

here is my testing program

Code:

#if defined(__PCM__)
#include <16F819.h>
#device *=16
#include <stdio.h>
#include <stdlib.h>
#fuses XT,NOWDT,NOPROTECT,NOBROWNOUT
//#device ADC=10
#use delay(clock=4000000)
#use rs232(baud=2400, parity=N, xmit=PIN_A0, rcv=PIN_A1)

int8 length,i, status;
char datar[20],datat[8][10],data;

void main()
{
   SET_TRIS_b(0xff);
   set_Tris_a(0x00);
   SETUP_CCP1(CCP_OFF);
   SETUP_ADC_PORTS(NO_ANALOGS);
   disable_interrupts(INT_EXT);
   disABLE_INTERRUPTS(GLOBAL);
   status=0;
   i=0;
   while(1)
   {
       putc(85);
    //   delay_ms(100);
    //  puts("how strange it is!");
   }
}
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Fri Feb 18, 2005 11:24 am     Reply with quote
You should be using EC_IO instead of XT

EC stands for External Clock the IO stands for input/output which is what you gain since you are only using 1 pin instead of 2
young



Joined: 24 Jun 2004
Posts: 285

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PostPosted: Fri Feb 18, 2005 11:26 am     Reply with quote
I think for the fuse, I should use HS instead of XT!
young



Joined: 24 Jun 2004
Posts: 285

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PostPosted: Fri Feb 18, 2005 11:30 am     Reply with quote
Thank you mark:

I tried both HS and EC_IO, they all doing good. maybe EC_IO is even more stable.
young



Joined: 24 Jun 2004
Posts: 285

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PostPosted: Fri Feb 18, 2005 11:40 am     Reply with quote
regarding to the code, I have another part of the code to test the signal stability using another chip

here is the code



Code:

if defined(__PCM__)
#include <16F819.h>
#device *=16
#include <stdio.h>
#include <stdlib.h>
#fuses HS,NOWDT,NOPROTECT,NOBROWNOUT
//#device ADC=10
#use delay(clock=20000000)
#use rs232(baud=9600, parity=N, xmit=PIN_A0, rcv=PIN_A1)

int8 length,i, status;
char datar[20],datat[8][10],data;

int32 overflow_count;
unsigned int32 start_time, end_time;
unsigned int32 pulse_ticks;

#int_TIMER1
TIMER1_isr()
{
   ++overflow_count; //increment whenever an overflow occurs;
}

#int_CCP1
CCP1_isr()
{
   end_time=CCP_1; //read captured timer ticks
   pulse_ticks=(0x10000*overflow_count)-start_time+end_time;
   start_time=end_time;
   overflow_count=0;   //clear overflow counts
}



void main()
{
   SET_TRIS_b(0xff);
   set_Tris_a(0x00);
   SETUP_ADC_PORTS(NO_ANALOGS);
   SETUP_CCP1(CCP_CAPTURE_RE);
   setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
   enable_interrupts(INT_TIMER1);   //unmask timer1 overflow interrupt
   enable_interrupts(INT_CCP1);
   enable_interrupts(global);
   status=0;
   i=0;
   while(1)
   {
   printf("Frequency reading: %lu\r\n",pulse_ticks);
   delay_ms(200);

   }
}


I keep getting gabarge print out like this,

Quote:

\0AFrequenãy reading: 4170\0D
\0AFrequency reading: 4160\0D
\0AFrequency reading: 4170\0D
\0AFòequency reading: 4155\0D
\0AFòequency råading: 4170\0D
\0AFrequency reading: 4170\0D
\0AFreque


any idea what might be wrong?
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Fri Feb 18, 2005 11:41 am     Reply with quote
Look, if you are using an external clock the then EC_IO. Read the datasheet, it tells you in there.
young



Joined: 24 Jun 2004
Posts: 285

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PostPosted: Fri Feb 18, 2005 12:04 pm     Reply with quote
Hi mark:

Thank you: I already tried that it was the same result.
libor



Joined: 14 Dec 2004
Posts: 288
Location: Hungary

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PostPosted: Fri Feb 18, 2005 5:22 pm     Reply with quote
Is it a crystal? Then connect it to both pins with capacitors, as shown in the datasheet.
Is it a complete oscillator (i.e. external clock)? Then connect its output to CLKI pin only.
Guest
PostPosted: Mon Feb 21, 2005 7:23 am     Reply with quote
http://www.ecsxtal.com/pdf3/ECS_100.pdf said it is a Clock Oscillator

so which catagory it belongs to? I think it belongs to just a oscillator, is it right?
so I just need to connect to CLKI?
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Mon Feb 21, 2005 8:05 am     Reply with quote
It is a clock and goes to the CLKI pin and for the last time you should be using EC_IO!
Guest
PostPosted: Thu Jul 07, 2005 3:19 pm     Reply with quote
young wrote:
regarding to the code, I have another part of the code to test the signal stability using another chip

here is the code



Code:

if defined(__PCM__)
#include <16F819.h>
#device *=16
#include <stdio.h>
#include <stdlib.h>
#fuses HS,NOWDT,NOPROTECT,NOBROWNOUT
//#device ADC=10
#use delay(clock=20000000)
#use rs232(baud=9600, parity=N, xmit=PIN_A0, rcv=PIN_A1)

int8 length,i, status;
char datar[20],datat[8][10],data;

int32 overflow_count;
unsigned int32 start_time, end_time;
unsigned int32 pulse_ticks;

#int_TIMER1
TIMER1_isr()
{
   ++overflow_count; //increment whenever an overflow occurs;
}

#int_CCP1
CCP1_isr()
{
   end_time=CCP_1; //read captured timer ticks
   pulse_ticks=(0x10000*overflow_count)-start_time+end_time;
   start_time=end_time;
   overflow_count=0;   //clear overflow counts
}



void main()
{
   SET_TRIS_b(0xff);
   set_Tris_a(0x00);
   SETUP_ADC_PORTS(NO_ANALOGS);
   SETUP_CCP1(CCP_CAPTURE_RE);
   setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
   enable_interrupts(INT_TIMER1);   //unmask timer1 overflow interrupt
   enable_interrupts(INT_CCP1);
   enable_interrupts(global);
   status=0;
   i=0;
   while(1)
   {
   printf("Frequency reading: %lu\r\n",pulse_ticks);
   delay_ms(200);

   }
}


I keep getting gabarge print out like this,

Quote:

\0AFrequenãy reading: 4170\0D
\0AFrequency reading: 4160\0D
\0AFrequency reading: 4170\0D
\0AFòequency reading: 4155\0D
\0AFòequency råading: 4170\0D
\0AFrequency reading: 4170\0D
\0AFreque


any idea what might be wrong?
Guest
PostPosted: Thu Jul 07, 2005 3:20 pm     Reply with quote
young wrote:
regarding to the code, I have another part of the code to test the signal stability using another chip

here is the code



Code:

if defined(__PCM__)
#include <16F819.h>
#device *=16
#include <stdio.h>
#include <stdlib.h>
#fuses HS,NOWDT,NOPROTECT,NOBROWNOUT
//#device ADC=10
#use delay(clock=20000000)
#use rs232(baud=9600, parity=N, xmit=PIN_A0, rcv=PIN_A1)

int8 length,i, status;
char datar[20],datat[8][10],data;

int32 overflow_count;
unsigned int32 start_time, end_time;
unsigned int32 pulse_ticks;

#int_TIMER1
TIMER1_isr()
{
   ++overflow_count; //increment whenever an overflow occurs;
}

#int_CCP1
CCP1_isr()
{
   end_time=CCP_1; //read captured timer ticks
   pulse_ticks=(0x10000*overflow_count)-start_time+end_time;
   start_time=end_time;
   overflow_count=0;   //clear overflow counts
}



void main()
{
   SET_TRIS_b(0xff);
   set_Tris_a(0x00);
   SETUP_ADC_PORTS(NO_ANALOGS);
   SETUP_CCP1(CCP_CAPTURE_RE);
   setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
   enable_interrupts(INT_TIMER1);   //unmask timer1 overflow interrupt
   enable_interrupts(INT_CCP1);
   enable_interrupts(global);
   status=0;
   i=0;
   while(1)
   {
   printf("Frequency reading: %lu\r\n",pulse_ticks);
   delay_ms(200);

   }
}


I keep getting gabarge print out like this,

Quote:

\0AFrequenãy reading: 4170\0D
\0AFrequency reading: 4160\0D
\0AFrequency reading: 4170\0D
\0AFòequency reading: 4155\0D
\0AFòequency råading: 4170\0D
\0AFrequency reading: 4170\0D
\0AFreque


any idea what might be wrong?
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Jul 07, 2005 3:34 pm     Reply with quote
You're using a software UART, which uses software delay loops to
set the length of the transmitted bits. Then, you have interrupt
routines which are interrupting those software delay loops.
The result is the bit times are made longer than normal, which
causes your transmitted data to be corrupted.

You could disable interrupts while you're transmitting RS232 characters
by adding the DISABLE_INTS parameter to your #use rs232() statement.
But this might add too much latency to your CCP interrupt. I don't
know what your input signal is, or what you are measuring.

My suggestion:
Use a PIC that has a hardware UART. Then you eliminate this problem.
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