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I2C with 16F690 slave to master problem

 
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mvanvliet



Joined: 02 Jun 2009
Posts: 123
Location: The Netherlands

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I2C with 16F690 slave to master problem
PostPosted: Thu Mar 24, 2011 5:30 am     Reply with quote
I'm trying to send data between two 16F690 units, from the master to the slave and back, but when I send data to the slave the led goes on, so I think the data is received correct on the slave, but back to the master isn't working. Does anyone knows or sees the problem?

compiler version: 4.106

Master code:

Code:

#include <16F690.H>
#fuses INTRC_IO, NOWDT, NOPROTECT, NOBROWNOUT, PUT, NOMCLR, NOCPD, NOPUT
#use delay(clock=4000000) 
#use i2c(MASTER, SDA=PIN_B4, SCL=PIN_B6)

#define SLAVE_WRT_ADDR   0xa0
#define SLAVE_READ_ADDR  0xa1

void main()
{
   int8 data;
   int8 receive = 0;
   while(1)
   {
      //write to the slave board
      i2c_start();
      i2c_write(SLAVE_WRT_ADDR);
      i2c_write(0x00);
      i2c_write(10);
      i2c_stop();
     
      // Read from the slave board
      i2c_start();
      i2c_write(0xA0);
      i2c_write(0x00);
      i2c_start();
      i2c_write(SLAVE_READ_ADDR);
      receive = i2c_read(0);
      i2c_stop();
     
      if(receive == 10)
      {
      delay_ms(200);
      output_toggle(pin_b7);
      }         
   }
}


Slave code:

Code:

#include <16F690.h>
#fuses INTRC_IO, NOWDT, NOPROTECT, NOBROWNOUT, PUT, NOMCLR, NOCPD, NOPUT
#use delay(clock=4000000) 
#use i2c(SLAVE, SDA=PIN_B4, SCL=PIN_B6, ADDRESS=0xa0)

int8 incoming = 0, state;

#INT_SSP
void ssp_isr(void)
{
state = i2c_isr_state();
if(state < 0x80)     // Master is sending data
  {
   incoming = i2c_read();

   if(incoming == 10)
      {
      output_high(PIN_B7);
      }
     
  }
if(state >= 0x80)   // Master is requesting data from slave
  {
   i2c_write(incoming);
  }

}

void main ()
{
setup_adc_ports(NO_ANALOGS);//
enable_interrupts(INT_SSP);
enable_interrupts(GLOBAL);

while(1)
{
}

}


Thanks!
Ttelmah



Joined: 11 Mar 2010
Posts: 19538

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PostPosted: Thu Mar 24, 2011 6:17 am     Reply with quote
Your problem is 'incoming'.
When you try to read, you _write_ the register address to talk to. '0'. This is put into incoming. So the subsequent reply, will never be '10'.
This is why the normal method is to use a temporary variable 'dummy' (say), and have an array of actual storage locations, then set the address of the array from the first byte written (the address), and the contents from the second. If you then read back from the array, it is the address that gets set, by the address write, not the contents.

Best Wishes
mvanvliet



Joined: 02 Jun 2009
Posts: 123
Location: The Netherlands

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PostPosted: Thu Mar 24, 2011 7:01 am     Reply with quote
Thanks for your reply! Do you mean something like this:



Code:

#INT_SSP
void ssp_interupt (){
BYTE incoming, state;

state = i2c_isr_state();
       
if(state <= 0x80)                     //Master is sending data
    {
    incoming = i2c_read();
    if(state == 1)                    //First received byte is address
        address = incoming;
    if(state == 2)                    //Second received byte is data
        buffer[address] = incoming;
    }
if(state == 0x80)                     //Master is requesting data
    {
    i2c_write(buffer[address]);
    }
}
mvanvliet



Joined: 02 Jun 2009
Posts: 123
Location: The Netherlands

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PostPosted: Thu Mar 24, 2011 7:38 am     Reply with quote
It's working with this code in the slave:

Code:

#include <16F690.h>
#fuses INTRC_IO, NOWDT, NOPROTECT, NOBROWNOUT, PUT, NOMCLR, NOCPD, NOPUT
#use delay(clock=4000000) 
#use i2c(SLAVE, SDA=PIN_B4, SCL=PIN_B6, ADDRESS=0xa0)

int8 incoming = 0, state;

BYTE address, buffer[0x10];

#INT_SSP
void ssp_isr(void)
{
state = i2c_isr_state();
if(state < 0x80)     // Master is sending data
  {
    incoming = i2c_read();

    if(state == 1)                    //First received byte is address
        address = incoming;
    if(state == 2)                    //Second received byte is data
        buffer[address] = incoming;

  }
if(state >= 0x80)   // Master is requesting data from slave
  {
   i2c_write(buffer[address]);
  }

}

void main ()
{
setup_adc_ports(NO_ANALOGS);//
enable_interrupts(INT_SSP);
enable_interrupts(GLOBAL);

while(1)
{
}

}
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