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I2C SW working... I2C HW don�t?

 
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Mc



Joined: 07 May 2004
Posts: 11

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I2C SW working... I2C HW don�t?
PostPosted: Fri May 07, 2004 6:26 am     Reply with quote
Hi guys! I'm new to CCS C and I'm having some trouble getting the I2C HW working...

If I use #use i2c(Master,Fast,sda=PIN_C4,scl=PIN_C3) it works OK:

Program running
I2C init ok
Write: 00 02 04 06 08 0A 0C 0E
Read: 00 02 04 06 08 0A 0C 0E

but when I force HW I2C instead with #use i2c(Master,Fast,sda=PIN_C4,scl=PIN_C3,force_hw) it gets stuck:

Program running
I2C init ok

Confused


Here's my sample code, I use routines from 2465.C with some changes to fit my needs:

Code:
#include <16F876.h>

#use delay(clock=4000000)
#fuses NOWDT,XT,NOPUT,NOPROTECT,BROWNOUT,NOLVP,NOCPD,NOWRT,NODEBUG
#define EEPROM_SCL   PIN_C3
#define EEPROM_SDA   PIN_C4
#use rs232(baud=19200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,errors)
#use i2c(Master,Fast,sda=PIN_C4,scl=PIN_C3)
//#use i2c(Master,Fast,sda=PIN_C4,scl=PIN_C3,FORCE_HW)

#define hi(x)  (*(&x+1))

void i2c_init (void)
{
   output_float(EEPROM_SCL);
   output_float(EEPROM_SDA);
}

int1 i2c_device_ready (int8 i2c_slave_address)
{
   int1 ack;
   i2c_start();         // Si se admite petici�n de escritura entonces
   ack = i2c_write(i2c_slave_address);  // el dispositivo est� listo
   i2c_stop();
   return !ack;
}

void i2c_buffer_write_16 (int8 *i2c_buffer, int8 i2c_slave_address, int16 address0, int8 i2c_data_number)
{
   int8 i;
   while(!i2c_device_ready(i2c_slave_address));
   i2c_start();
   i2c_write(i2c_slave_address);    // controlbyte (write)
   i2c_write(hi(address0));
   i2c_write(address0);
   for(i=0;i<i2c_data_number;i++) i2c_write(i2c_buffer[i]);
   i2c_stop();
}

void i2c_buffer_read_16 (int8 *i2c_buffer, int8 i2c_slave_address, int16 address0, int8 i2c_data_number)
{
   int8 i;
   while(!i2c_device_ready(i2c_slave_address));
   i2c_start();
   i2c_write(i2c_slave_address);    // controlbyte (write)
   i2c_write(hi(address0));
   i2c_write(address0);
   i2c_start();
   i2c_write(i2c_slave_address+1);  //controlbyte (read)
   for(i=0;i<i2c_data_number-1;i++) i2c_buffer[i]=i2c_read();  //n-1 data->read+ack
   i2c_buffer[i2c_data_number-1]=i2c_read(0);   //last data->read+noack
   i2c_stop();
}


#define I2CREGS 8

void main()
{
   int8 i;
   int8 i2c_buffer[I2CREGS];

   for (i=0;i<I2CREGS;i++) i2c_buffer[i]=2*i; //0,2,4,6,8,10,12,14

   setup_adc_ports(RA0_ANALOG);
   setup_adc(ADC_CLOCK_DIV_32);
   setup_spi(FALSE);
   setup_counters(RTCC_INTERNAL,RTCC_DIV_256);
   setup_timer_1(T1_DISABLED);
   setup_timer_2(T2_DISABLED,0,1);

   printf("Program running\n\r");

   i2c_init();

   printf("I2C init ok\n\r");

   i2c_buffer_write_16(i2c_buffer,0xA0,0x00,I2CREGS);

   printf("Write: ");
   for(i=0;i<I2CREGS;i++) printf("%X ",i2c_buffer[i]);
   printf("\n\r");

   i2c_buffer_read_16(i2c_buffer,0xA0,0x00,I2CREGS);

   printf("Read:  ");
   for(i=0;i<I2CREGS;i++) printf("%X ",i2c_buffer[i]);
   printf("\n\r");

   while(1);
}


I'm using an 16F876 @ 4MHz, CCS v3.187 and I'm testing the I2C with a 24LC64 EEPROM...

Any idea??

Thanx in advance Wink
Haplo



Joined: 06 Sep 2003
Posts: 659
Location: Sydney, Australia

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PostPosted: Fri May 07, 2004 6:47 am     Reply with quote
Make sure RC3 and RC4 are configured as inputs. Have you tried taking the 'fast' keyword out to see if it works? How big are your pull-ups?
Mc



Joined: 07 May 2004
Posts: 11

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PostPosted: Fri May 07, 2004 7:24 am     Reply with quote
Thanx for the quick answer!

Manually setting PORTC as inputs with set_tris_c(0xFF); doesn't solve the problem, maybe RS232 routines are overwiting this setting??

My pull-ups are 2k2 each. In 'Slow' mode it doesn�t work either.

Also I think that I don't have to output float the i2c pins while using i2c hw, I tried to comment

output_float(EEPROM_SCL);
output_float(EEPROM_SDA);

but still no luck...

I guess there's no HW related problem since I've been working with I2C HW ASM routines in the same board not so long ago with no issues whatsoever...
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri May 07, 2004 12:06 pm     Reply with quote
I would guess that you're probably using PCW.

If you don't use a peripheral module, PCW puts in code to
explicitly disable it. This isn't really necessary, because the
peripheral modules are disabled by default upon power-up.

The problem is caused by this line of code:
setup_spi(FALSE);

That line sets the SSPCON register to 0x00. So it affects
the entire SSP module, and not just "spi", as the function name
suggests. It writes a 0 to the SSPEN bit in that register.
According to the data sheet:

bit 5 SSPEN: Synchronous Serial Port Enable bit
0 = Disables serial port and configures these pins as I/O port pins

That's why it's not working. The solution is to delete that line.
kender_a
Guest
Same problem.
PostPosted: Fri May 07, 2004 2:22 pm     Reply with quote
Hello,

I have the same problem - I2C stops worling if is specify FORCE_HW. But I don't have a call to setup_spi() anywhere in my code. Here's my code:

Code:


#include <18F442.h>
#device ICD=TRUE
#device adc=8
#use delay(clock=4000000)
#fuses NOWDT,WDT128,XT, NOPROTECT, NOOSCSEN, BROWNOUT, BORV20, NOPUT, STVREN, DEBUG, LVP, NOWRT, NOWRTD, NOWRTB, NOWRTC, NOCPD, NOCPB, NOEBTR, NOEBTRB
#use rs232(DEBUGGER)
#use i2c(Master,sda=PIN_C4,scl=PIN_C3,force_hw)


#include "i2ctest.h"


void main()
{

   setup_adc_ports(NO_ANALOGS);
   setup_adc(ADC_OFF);
   setup_psp(PSP_DISABLED);
   setup_wdt(WDT_OFF);
   setup_timer_0(RTCC_INTERNAL);
   setup_timer_1(T1_DISABLED);
   setup_timer_2(T2_DISABLED,0,1);
   setup_timer_3(T3_DISABLED|T3_DIV_BY_1);
   
   
   while (1)
   {
      // single write to EEPROM
      i2c_start();
      i2c_write(0b10100000);  // command byte
      i2c_write(0x01);        // address
      i2c_write(0xAA);        // data     
      i2c_stop();
     
      // single read from EEPROM
      i2c_start();
      i2c_write(0b10100000);  // command byte
      i2c_write(0x01);        // read address
      i2c_start();
      i2c_write(0b10100001);  // command byte     
      printf("%4X\n\r", i2c_read(1));  // end of the read
      i2c_stop();
     
      // page write to EEPROM
      // page read from EEPROM
      // write to DAC
      // read RTC
   }
}



I'm running this with the debugger, and the execution halts at "setup_adc_ports(NO_ANALOGS);"

What am I doing wrong?

Nick
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri May 07, 2004 2:33 pm     Reply with quote
Quote:
I have the same problem - I2C stops working if I specify FORCE_HW


Quote:
I'm running this with the debugger, and the execution halts
at "setup_adc_ports(NO_ANALOGS);"


These are two separate complaints. I'll answer the one about
the i2c problem.

You have this line of code:
printf("%4X\n\r", i2c_read(1));

That's wrong. The last i2c read must do a "NAK".
It should be:
printf("%4X\n\r", i2c_read(0));
kender_a
Guest
NACK worked
PostPosted: Fri May 07, 2004 2:52 pm     Reply with quote
Thanks, switching to i2c_read(0) worked, and formware doesn't halt at setup_adc_ports(NO_ANALOGS) too.

I have another question though. I have to pause for about 5ms between the read and the write. Otherwise I read 0xFF. Can this pause be avoided? Here's my code again:

Code:

while (1)
   {
      // single write to EEPROM
      i2c_start();
      i2c_write(0b10100000);  // command byte
      i2c_write(0x01);        // address
      i2c_write(i);        // data     
      i2c_stop();
     
      delay_ms(5);
     
      // single read from EEPROM
      i2c_start();
      i2c_write(0b10100000);  // command byte
      i2c_write(0x01);        // read address
      i2c_start();
      i2c_write(0b10100001);  // command byte     
      printf("%4X\n\r", i2c_read(0));  // end of the read, NACK
      i2c_stop();
     
      // page write to EEPROM
      // page read from EEPROM
      // write to DAC
      // read RTC
     
      ++i;
      if (i == 255) i = 1;
   }
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri May 07, 2004 3:21 pm     Reply with quote
Quote:
I have another question though. I have to pause for about 5ms
between the read and the write. Otherwise I read 0xFF. Can this pause
be avoided?


The EEPROM data sheet will tell you that it takes about 5 ms for
the write operation to be completed. Look at page 4 of the
data sheet, at Parameter No. 17:
http://ww1.microchip.com/downloads/en/DeviceDoc/21203l.pdf

The two common ways to handle this are:

1. Put a delay_ms(5) statement at the end of the write operation.
ie., put it after the i2c_stop() statement at the end of the routine.
(Or use a slightly larger delay, such as 6 ms, to be extra safe).

2. Do "ack polling". This method is discussed in the 24LC256 data
sheet. CCS does this in their sample EEPROM drivers.
The drivers are in this directory:
c:\Program Files\Picc\Drivers
If you have the demo, you probably don't get these files.
dyeatman



Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK

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I2C Delay Required
PostPosted: Fri May 07, 2004 3:38 pm     Reply with quote
One way to eliminate the delay is to use FRAM which does not require a delay between the write and read....
Mc



Joined: 07 May 2004
Posts: 11

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PostPosted: Fri May 07, 2004 9:46 pm     Reply with quote
PCM programmer wrote:
The problem is caused by this line of code:
setup_spi(FALSE);
.
.
.
That's why it's not working. The solution is to delete that line.


Yep, that was the problem! Smile

Thanx a lot!! Wink
hayri
Guest
PostPosted: Sat Mar 19, 2005 9:53 am     Reply with quote
very old topic to post. but i must!

thanks a lot PCM programmer Smile it solved my problem.
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