I2CRead & I2CWrite not working as expected

[richard]

Only VDD/VSS and SDA/SCL pins are used, others are left floating, according to datasheet.

start a TEST first to see if your I2C unit is OK
let go here

or read the data sheet again and work out the consequences of floating address pins on the device address

[CuriousOne]

From the datasheet:


DEVICE/PAGE ADDRESSES (A2, A1, A0): The A2, A1 and A0 pins are device address
inputs that are hard wired or left not connected for hardware compatibility with
AT24C16. When the pins are hardwired, as many as eight 32K/64K devices may be
addressed on a single bus system (device addressing is discussed in detail under the
Device Addressing section). When the pins are not hardwired, the default A2, A1, and A0
are zero.
WRITE PROTECT (WP): The write protect input, when tied to GND, allows normal write
operations. When WP is tied high to VCC, all write operations to the upper quandrant
(8/16K bits) of memory are inhibited. If left unconnected, WP is internally pulled down to
GND.

The A2, A1, and A0 pins use an internal proprietary circuit that biases them
to a logic low condition if the pins are allowed to float.

[richard]

to my surprise i found the 24c32 on my ds3231 module did not behave as expected when the resistor block [circled] was removed
to conserve energy for a battery device


the address was still 0xAE, contrary to the datasheet , so i looked at a data sheet from another manufacturer, where for a 24c32n
they did not describe this address pin biased low behavior for their version

to ensure 0xA0 the pins needed to be grounded

so how sure are you that the datasheet matches the chip?
its an easy test

[CuriousOne]

I will try grounding. I will also hook up scope to see what happens.
I do have pull up resistors in place for SDA/SCL pins.
Regarding how I know about datasheet?
I bought this IC from digikey, and downloaded datasheet from the SKU page
This is genuine atmega part.

[Ioannis]

It could be that a static discharge killed the pull down circuitry, so the floating pins may not be a $A0 anymore.

I had in the past various issues with static and decided to be almost paranoid with this thing. Have anti-static mate on the floor, also on the bench and I earth my self too. Of course the soldering iron is earthed too by a tens of kΩ range resistor.

Chips from various vendors also have differences and datasheet may not cover that. Richard is right.

Ioannis

[CuriousOne]

Here I connected the scope.
This is how this code looks:
My scope (Hantek DSO2D10) Has I2C decode function, but I can't get it running properly.

mainloop:


   For B0 = 0 To 15 step 2  
     I2CREAD DPIN,CPIN,$A0,B0,X  
     lcdout $fe, $1, dec b0, " ", dec X 
     pause 1000
   Next B0


Goto mainloop

[CuriousOne]

Oh by the way, I swapped chip with 24C04N - no difference.