i2c questions / debug

[Wawavoun]

Hello All,

I try to talk i2c to a DS3231 module.

First I try to read the temperature. I do that with a 6809 proc and a 6522 via on B port bit 0 and 1.

The DS3231 reply with a great constancy $FF for temperature MSB and LSB.

The recording of the i2c session is here.



The point looking strange is that the DS3231 reply NACK to device selection, to data write instruction and to address to read... Reading the datasheet this should be a ACK.

Can somebody point to me what is wrong in the transmission

Thanks and regards.
Philippe

[Peabody]

An ACK is bringing the data line low for one clock cycle.  A NAK is simply not doing anything.  So perhaps the DS3231 is not able to bring the data line low under any circumstance.   That would also account for the temp register being all FFs.  You might check your wiring.

Edit:  Perhaps the DS3231 isn't even powered up.  What different results do you get from your test code if the DS3231 is not connected at all?

[Wawavoun]

You are right.
Without DS3231 module signals are the same...

I have to think !

[pcprogrammer]

I noticed that you made a double post on this subject. Please do not do that.