DS2431 wrong answer (0x55) at Copy Scratchpad Command

[bauergeorg]

Hi folks,
we are using OneWireHub and we are very happy about this cool project. Thanks a lot!

Bug
By using the DS2431 with an own server implementation we found a hysteric behavior by writing memory function.
I found a different behavior between the real chip and the emulation. The real chip answers with 0xAA, the emulation answers with 0x55 (or different) during the “Copy Scratchpad” procedure.

Here is an extract of the DS2431s datasheet.

Below you can see a timing diagram of a logic analyzer (Saleae Logic Analyzer) of the real chip (Answer 0xAA):

Below you can see a timing diagram of a logic analyzer (Saleae Logic Analyzer) of the emulated chip (Answer 0x55):

Environment

• We found the line in the code. But we can’t find any error. It looks perfect.
• We used a Arduino Nano and a Arduino Uno. Same devices showed the same behavior (answering 0x55).
• Changing the timing behavior (changing a little bit the code) we saw in some case an answer 0xFF.
• We checked the same behavior with two one-wire-master applications: an own python application and Maxim's OneWireViewer.

Thank's a lot!

Georg