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Subject: Re: Serial remote code "STOP" (0xC2) partially not working

Re: Serial remote code "STOP" (0xC2) partially not working

From: Steve Russell <>
Date: Sat, 20 Mar 2004 18:40:18 -0000

"Matthias Klumpp" <> wrote in message

> Hardware connection is done via open-collector to the serial data pin of
> headphones connector with negative logic.

I assume you have this correct, as you say that most of the commands work,
but are you sure you mean negative logic? It should be positive logic: 1 is
o/c transistor is OFF (high voltage to input pin), 0 is transistor ON (0V to
input pin).

> Some members were telling me the supported codes, that are:
> Volume down = 0xE0, Volume up = 0xD0, Next = 0xC8, Previous = 0xC4, Stop =
> 0xC2, Play = 0xC1.

The REMOCLONE only uses 6 bits, but my remote sends 8 - from the JBR's point
of view, there's little difference, since the two extra bits have the same
value as the stop bit (1). I chose to transmit 8 bits as it will allow me
complete flexibility to define new commands should the Rockbox team
implement new functions to control from the remote. I'm not sure how many
bits the JBR actually receives (6 or 8). For example, I've had a request to
implement Start Record from the remote, but there's no way to do so at
present. However, there's nothing to stop Rockbox defining a "One-Touch
Record" command.

> If I'm sending the 0xC2 stop command while a file is playing, the AJB does
> not react.

As we've discussed offline, my remote send 0xC2 and a playing song stops as

> If I have backlight dimmed down, I can observe, that the backlight goes
> That again tells me, that the AJB is receiving data, but still does not
> react.

Without looking at the Rockbox source, it could be that the backlight goes
on as soon as a start bit transition is received - it may not indicate
correct reception of a command.

> Does anybody have an idea how to solve this ?

Do you have the ability to tweak the bitrate of your UART? Just in case your
timing is marginal?

Good luck, Steve.

Received on 2004-03-20

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