I'm currently working on reverse engineering the protocol that my Subaru uses to control its cd-changer from the head unit. From the information I've gathered, the changer and head unit communicate via a 1 wire serial interface, however I haven't found anyone who has actually attempted to log the data being transmitted between the two devices.
My problem is, I'm not sure of what logic levels are being used for communication. I am hoping that the serial line is pulled high until one device want's to talk, I could easily measure the voltage then. Does anyone have any ideas on how to measure the voltages being used? I've got a pretty basic multimeter, a logicport logic analyzer, and random components to work with. Unfortunately I don't have access to an o-scope. Also, I'd rather not take the radio apart since it is expensive.
Attached is the connector for the cd-changer. BUS LINE is the serial interface. +B is the battery, and ACC is accessory power.
Also, if anyone knows what type of connector that is, or how to figure it out, I'd love to know!
EDIT: I just did a search and found the part of the service manual for the radio.
According to this, it's labeled CN702 16P Connector.
Thanks in advance!