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I2c doesn't work

 
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Pekub



Joined: 20 Dec 2005
Posts: 16

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I2c doesn't work
PostPosted: Sun Mar 18, 2007 10:35 am     Reply with quote
I tried i2c communication between 18F2420 / Master/ and 18F4420 / Slave/. It doesn't work. I used ex_slave.c code for slave and standard master code. When I used on slave side 16F877A, communication worked properly.

Tried anyone i2c with these new procesors? /18F4420, 18F2420/.

Master code:

Code:
...
i2c_start();
i2c_write(0xA0);
i2c_write(0x00);
i2c_start();
i2c_write(0xA1);
data = i2c_read(0);
i2c_stop();
...


Slave code:

1. ex_slave.c

2. I tried slave code from Ttelmah.
It doesn't work too.

Code:

#ifdef __PCM___
 #byte SSPCON=0x14
 #byte SSPSTAT=0x94
 #byte SSPBUF=0x13
#else
 #byte SSPCON=0xFC6
 #byte SSPSTAT=0xFC7
 #bit SSPBUF=0xFC9
#endif
#bit P=SSPSTAT.4
#bit DA=SSPSTAT.5
#bit S=SSPSTAT.3
#bit RW=SSPSTAT.2
#bit BF=SSPSTAT.0
#bit WCOL=SSPCON.7
#bit SSPOV=SSPCON.6
#bit SSPEN=SSPCON.5

//My I2C buffer
#define BSIZE 32;
//Note buffer size must be binary multiple
int8 buffer[BSIZE];

#define read_i2c() (SSPBUF)
#define write_i2c(x) SSPBUF=(x)
#define MWLBA ((S==1)&&(RW==0)&&(DA==0)&&(BF==1))
#define MWLBD ((S==1)&&(RW==0)&&(DA==1)&&(BF==1))
#define MRLBA ((S==1)&&(RW==1)&&(DA==0)&&(BF==0))
#define MRLBD ((S==1)&&(RW==1)&&(DA==1)&&(BF==0))
#define MNACK ((S==1)&&(RW==0)&&(DA==1)&&(BF==0))
//Note that for the 18 chips, you could add GCEN as another bit to test

#int_SSP
void SSP_int_handler(void) {
 static int8 ctr;
 int8 tmp;
 if(MWLBA) {
  //Here I have an address match for a write operation
  ctr=0;
  tmp=read_i2c();
 }
 else if(MWLBD) {
  //Here data arriving from master
  buffer[ctr++]=read_i2c();
  ctr &= (BSIZE-1);
  //Limit buffer counter to buffer size
 }
 else if(MRLBA) {
  //Here an address match for a read command
  ctr=0;
  write_i2c(buffer[ctr++]);
 }
 else if(MRLBD) {
  //Here sending data to master
  write_i2c(buffer[ctr++]);
  ctr &= (BSIZE-1);
 }
 else if(MNACK) {
  //Here NACK from master
  SSPEN=0;
  SSPEN=1;
  //Reset I2C module
 }
 if (SSPOV) SSPOV=0;
 if (WCOL) WCOL=0;
}

[/code]
Ttelmah
Guest
PostPosted: Sun Mar 18, 2007 1:00 pm     Reply with quote
Look at initialisation.
On the latter chips, the I2C hardware, is often multiplexed with other peripherals, and/or, may require specific fuses to set which bits are used. This initialisation needs to be right if the peripheral is going to work.

Best Wishes
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