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Subject: Re: ANNOUNCE: Rockbox emulates M-Bus car CD changer (Alpine and OEM)
From: jobarjo (jobarjo78_at_yahoo.fr)
Date: 2004-02-13


I didn't mean to poll.
If I understood correctly, there is a PIO connected to the remote pin.
I dont know if it is possible in the archos, but it might be possible to
trigger an interrupt at each transition. The interrupt handler measures the
time to the previous transition with a timer and write the value in a
buffer. It might also call a handling routine which converts the time
between transitions to numeric values (depends on the encoding : serial,
sony slink, mbus, infrared...).
This low level protocol handler could then call an higher level protocol
handler which would interact with the player and may respond with the same
signal.

To trigger an interrupt at each transition, the handler just switches the
interrupt polarity at each transition.

When the high level protocol decides to transmit data, it just disable the
interrupt for the input and then it can drive the remote pin.

This technique of setting the interrupt handler for each transition is used
in the universal infrared receiver design. I think that it is generic enough
to provide a general purpose remote control api.

I've read about the sony s-link, which seems very similar to the M bus
encoding (pulses to encode 0 and 1) it is also compatible with this generic
technique.

The sony S-link seems more interesting to me because sony pilot changer are
cheap and widespread. The protocol is also well documented. It is even
possible to display song names.

----- Original Message -----
From: "[IDC]Dragon" <idc-dragon_at_gmx.de>
To: "Rockbox development" <rockbox_at_cool.haxx.se>
Sent: Friday, February 13, 2004 3:16 PM
Subject: Re: ANNOUNCE: Rockbox emulates M-Bus car CD changer (Alpine and
OEM)

> > Just another silly question: Where did you find the 8 pin DIN
connector?
> What do you mean, the pinout or the physical plug? I was citing a URL for
> the pinout.
>
> > I now have to look around for a compatible cd changer, the 4 pin jack
and
> > the DIN...
>
> Don't look for a changer, you need the radio. The Archos becomes the
> changer.
>
> > Hope I can find a still compatible changer. Do you think that any 8 pin
> > DIN
> > connector will be M-Bus compatible?
>
> Very likely.
>
> > I dont think the remote api is so exotic. As you said, lot of people is
> > looking for remote controlling the archos. There are lot of ways of
> > controling the archos.
> >
> > As for the universal remote control, the principle is to mesure the time
> > distance between logical switches with an interrupt and a timer. It is
> > then
> > easy to convert these distances to values according to the protocol.
>
> No, it's more involved. Don't forget that the changer protocol is
> bidirectional, we need to send, too. And then I want specific timeouts,
etc.
> In fact I do the receiving with the UART feature of the CPU (generating
> interrupts, so I don't have to poll) and the sending by setting pulse
edges in a
> timer interrupt.
>
> Jörg
>
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