I'm having trouble figuring out how to use I2C from within the C18
compiler. Here's my code
 to read a byte from an X1226:

 unsigned char ReadU8eep(unsigned int addr){
 // Read a byte from eeprom chip at addr
 unsigned char data; // Keep our data while we close the I2C
 OpenI2C(MASTER, SLEW_ON); // Initialize the I2C as a master
 // SSPADD=22; // 400 kbps with 40 MHz clock
 SSPADD=0xff;
 IdleI2C(); // Wait for i2c to be ready
 StartI2C(); // Send a start
 IdleI2C(); // Wait for i2c to be ready
 WriteI2C(0xae); // Send the slave address with the r/-w low indicating
we're writing an
 address
 IdleI2C(); // Wait for i2c to be ready
 WriteI2C(0xff & (addr>>8)); // Send the high half of the address address
 IdleI2C(); // Wait for i2c to be ready
 WriteI2C(0xff & addr); // Send the low half of the address
 IdleI2C(); // Wait for i2c to be ready
 StartI2C(); // Send a start
 IdleI2C(); // Wait for i2c to be ready
 WriteI2C(0xaf); // Send slave address with r/-w high indicating we're
reading
 IdleI2C(); // Wait for i2c to be ready
 data=ReadI2C(); // Get the data
 IdleI2C(); // Wait for i2c to be ready
 StopI2C(); // Send an I2C stop
 IdleI2C(); // Wait for i2c to be ready
 CloseI2C(); // Done with I2C
 return(data); // Exit with the data we got
 }

      The documentation on the I2C library only gives sample code for
talking with Microchip
 EEPROMs, so I had to try to figure out how to talk with the Xicor part.
I'm assuming IdleI2C()
 is required between instructions to insure the SPP has finished the
previous instruction.
      Watching the transaction on a scope, the problem SEEMS to be with
the StartI2C() after
 sending the low half of the address. After the 8th clock, another clock
is sent and data is
 held low (I assume by the X1226) for an acknowledge. Then, the clock
goes low. The
 StartI2C() seems to do nothing. The clock and data both remain low.
After the acknowledge
 clock (about 12us) is a very short clock (less than 4us). It appears the
data line is released
 at the same time as the clock line. This MIGHT be an attempt at sending
a start, but it
 clearly fails. The clock goes low after the 4us or so while data remains
high through the next
 full clock (the start of sending 0xaf). When we get down to reading data
back using ReadI2C,
 the data line just stays high. I think the EEPROM ignored the command to
output its data
 because of the lack of a start.
      So, anyone done I2C using C18?

 Thanks!

 Harold


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