Hi Nicholas,

Nicholas you definitely want to initialize 'I2C_Address' otherwise your code
will not work:

Try this:

     char I2C_Address = 0x58;

Instead of:
     char I2C_Address;



The actual 7-bit slave device address for the way you wired the MAX517 (with
pins AD1, AD0 grounded) is 0x2C.
But when the slave address is coerced into the 8-bit 'I2C_Address' because
of the R/W bit, it becomes 0x58.
So you did your homework well and came up with 0x58. :)

Nicholas, I think your best course of action is to test the function return
code of the 'WriteI2C()' function like I mentioned in my last post. This
will provide you with some useful information. You should really test and
act upon the function return code in future code, but for now, just test the
return value to see what you get.

I've always written my own I2C routines in HI-TECH PICC, PICC-18, and
PICC-Lite. I have never used the Microchip C18 compiler.
You main goal is to see if your slave ACKs your control byte correctly -- I
would imagine that this status is reflected in 'WriteI2C()' funtion code
status.

Nicholas, in your pinout you said 'Pin 8 - No connection' -- this is where
you want to feed your voltage reference.
Isn't this the pin you said yesterday you connected to a voltage divider?
I'm confused now. You definitely do not want that pin as a NO CONNECT since
that's you voltage reference input. You could tie that pin to Vdd for now.
Then if you sent 0x7F to the DAC (output byte) you would expect
approximately Vdd/2 on your DAC output pin.

I'm about a day away from a Master I2C/SMBus Engine (MISE) release that
could validate your project I2C hardware in a few minutes.
The MISE utility give you interactive feedback on your I2C transactions so
that you'll know if the START condition worked, if the control byte was
ACKed by the slave, etc.


I'm assuming that the MAX517 does not have a half-buffered output (some DACs
like the TLC5620 do) -- just check the data sheet to make sure.


Make that change I mentioned above and please report back.

Good luck.

Ken Pergola

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