Post Go back to editing

LTC2945 communicate problem in reading

My schematic is simple as shown in datasheet, the VDD and INTVCC is powered by 3.3V.

The master communicated with the slave by using the common Mass Writeaddress (1100 110b).
When I read the REGISTER ADDRESS(02h) as figure 10, after the S(start), the slave acknowledged for the ADDRESS(1100 110b) after the master sent the W. Then, the master sent the command 02h, the slave acknowledged again. When I send repeated stat and address(1100 110b) to the slave, the slave did not acknowledge, either, it never answered the master.

The  frequency of SCL is 200kHz.

Any idea would be welcomed.
Thank you.

  • Greetings Switch,

       It's a little hard to tell based on the picture you sent, but I think I have an idea of what is causing your problem.  The I2C read word transaction looks fine up until the repeated start, but then it looks like immediately afterwards, SDA is going high right after SCL goes high, which would be interpreted as a STOP condition.  Could you please send some scope shots, if possible?  I have seen similar issues before and they are nearly always timing-related.

    Thank you and best regards,