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16F886 as an I2C Slave?

 
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16F886 as an I2C Slave?
PostPosted: Thu Feb 26, 2009 4:26 pm     Reply with quote
Has anyone gotten this to work? Unfortunately, I was counting on this in my design. I recently discovered the errata sheet, which lists some workarounds. I guess I'll be trying them. I am really wishing I had picked an older chip about now.
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PostPosted: Thu Feb 26, 2009 11:06 pm     Reply with quote
Actually, I have it working now. My compiler is version 4.086. I noticed that the I2C_Read() would return a value even if the slave was stopped at a breakpoint. I then figured that the master might be reading before the slave had time to respond. I put a 1 MS delay before the read and the master gets the proper data.

I believe that the delay is just a workaround, but at least I can make some progress again. I think the master should wait for the slave, maybe the slave is not stretching the clock properly. There is some info in the 16F886 errata sheet, but I haven't digested it completely. I plan to look at it some more in the near future.

Here is the code fragment that worked:

Code:

// Read from the slave board and display the data.
i2c_start();
i2c_write(0xA0);   // send i2c address w/ read bit clear
i2c_write(0x00);    // send data address
i2c_start();      // restart for read
i2c_write(0xA1);   // send i2c address w/ read bit set
delay_ms(1);            // wait for slave to respond
data = i2c_read(0);   // read data w/ no ack
i2c_stop();
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