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Subject: Re: ANNOUNCE: Rockbox emulates M-Bus car CD changer (Alpine and OEM)
From: [IDC]Dragon (
Date: 2004-02-13

> For the sony s-link it uses variable length pulses:
> might still be possible to hack with the uart. But the BIG problem is that
> there is an uncertainty on the last bit value for each byte received. So
> it does not seems easily feasible.

You could use the UART at high baudrate to just find the falling edges
(getting a framing error a byte time after it) and use that for your decoding.

> Is it possible to program a 600us timer interrupt to sample the pin after
> the first falling edge?

Yes, you can do that.

A general thing: most CD changer protocols require more than one line for
their communication. A naked Archos (without external uC addon) can't handle
that. I was "lucky" that Alpine uses only one pin (bidirectionally), and that
the levels are OK.


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