Tamagotchis can have three possibile interactions: visits, presents and games. Starting with the simplest, visits, I recorded a number of interactions. I noted that each visit involved either singing, playing ball or chatting. Below is a sample visit.

Singing visit between JANIE and HELEN

JANIE: ac 0 24 d6 a 1 e 9 5 0 4 88 0 0 20 80 9 0 0 ff 1 ff ff 0 (request)

HELEN: ac 1 1f 96 8 5 c 5 e 0 4 88 20 5 10 0 1 0 0 ff 1 ff ff 4e (response)

JANIE: ac 1c 24 d6 a 1 20 1f c (request confirmation)

HELEN: ac 1d 1f 96 8 5 20 24 cf (response confirmation)

Based on this (and several other samples)I theorize the following protocol:

Request and response:

Confirmations

When the Tamagotchis play a game instead of just visit, the request and response are the same, but the confirmations are different:

Likewise, when they give a present, only the confirmation is different.

So that's a ten second guide to the protocol!

Up next:

• Set up IR to send stuff to Tamagotchi
• Put a Tamagatchi into debug mode to better understand the physical attributes portion of the protocol
• Play with the protocol :)