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multi 24lc128s

 
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delene



Joined: 13 Oct 2003
Posts: 32

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multi 24lc128s
PostPosted: Tue Sep 18, 2012 2:30 am     Reply with quote
Hi

I recently upgraded my compiler to version 4.135 and now I have a problem. (Please don't ask how old the previous version was - you will be horrified - it goes back to one of the early 3 versions).

I have a card that has a pic 16f877a, a ds1307 and a 24lc128.
This is connected to a plug in card that has a 16f877a and two 24lc128s.

Since upgrading the compiler version, the data being read on the first card is sometimes corrupt. Sometimes it reads correctly and other times not.
I have found that if the second 16f877a is not plugged in, it correctly reads all the time.
What would be causing this?

I have tried setting it to multi master - makes no difference.
I know the hardware is right, because I have been using the hardware for the 15 years or so.

My code for reading the 128 is as follows - I have taken this from the example file, and have also changed it to the newer version as the one I was ready was a lot different.

I also tried the version that checks to see if the device is ready and that didn't work either.

Code:

#define EE_SDA  PIN_C4
#define EE_SCL  PIN_C3

#define hi(x)  (*((int8 *)&x+1))
#use i2c(multi_master, sda=EE_SDA, scl=EE_SCL)
#define EEPROM_ADDRESS long int
#define EEPROM_SIZE    16384

void init_ext_eeprom()
{
   output_float(EE_SCL);
   output_float(EE_SDA);
}

void write_ext_eeprom(long int address, BYTE data)
{
   short int status;
   i2c_start();
   i2c_write(eepromaddress);
   i2c_write(address>>8);
   i2c_write(address);
   i2c_write(data);
   i2c_stop();
   i2c_start();
   status=i2c_write(eepromaddress);
   while(status==1)
   {
      i2c_start();
      status=i2c_write(eepromaddress);
   }
   i2c_stop();
}

BYTE read_ext_eeprom(long int address)
{
   BYTE data;
   i2c_start();
   i2c_write(eepromaddress);
   i2c_write(address>>8);
   i2c_write(address);
   i2c_start();
   i2c_write(eepromaddress + 1);
   data=i2c_read(0);
   i2c_stop();
   return(data);
}
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Sep 18, 2012 12:44 pm     Reply with quote
Quote:
I have a card that has a pic 16f877a, a ds1307 and a 24lc128.
This is connected to a plug in card that has a 16f877a and two 24lc128s.

I assume this means you have the i2c bus on each board is connected
to the to other board, so it's one big i2c bus ?

That means you have two PIC masters on the same bus. What prevents
both the PICs from trying to access the bus at the same time ? Because
if they do, you will surely get errors.

Also, if you connect these two independent boards together, what's the
combined equivalent resistance for the pull-up resistors now ? And what's
the speed of your i2c bus clock ? Post your #use delay() statements
and your #use i2c() statements.
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