Rockbox mail archive
Subject: Re: remote control
From: Andreas Zwirtes (zwirtes_at_gmx.de)
We should not limit the interface by designing two resistors into the
cable. Here some resons why:
First point is that I already have plans for the charger circuit that we
might need and for a short circuit protection. That is very helpfull
when the controller (i.e. it's software) goes mad and pushes the line to
groud while Archos is trying to provide power.
Second point is that resistors are the all time cheapest parts, so why
not put them on every PCB and every interface? That would ease the cable
production. It is very annoying to solder resistors into a cable, but no
problem to put two resistors on a PCB.
Third point is that the smallest remote i can guess doesn't even have
room for the two resistors in the plug. I'm thinking of a PCB with a
very small Lithium battery that is only about 2-3 square centimeters in
size. It could use a very dumb and very small 8pin SOP (SMD) Tiny-AVR
device that is just able to send data. This PCB already contains the
short circuit protection and the charger circuit. It has only buttons to
give the basic remote functionality.
Fourth point is that we could use a very small two pin connector without
audio or an also very small four pin connector with audio. But with 6
pins you'll have a problem finding small connectors that are suitable
for small devices. In fact, you already have that problem with 4 pins.
We both already agreed that the Archos must not send anything, when no
remote or the original remote is connected. So in the very beginning,
the remote must be master to initiatiate the first communication. What i
do not understand is why we should mess up the protocol by switching the
master and slave functionality back and forth. The overhead is really
To keep in mind: When no remote is connected, I beleive the RX line of
the Archos is floating. That is very likely detected as a valid wakeup
or even as invalid communication. When in slave mode, the Archos will be
quiet and we do not have a problem at all.
Andreas Stemmer schrieb:
>My suggestion was concerning Stuarts idea to have the archos-specific
>parts not in the remote but in the cable between remote and archos.
>That would be the two resistors. This way, we could build another cable
>with a level converter and connect the remote to a PC instead of the
Page was last modified "Jan 10 2012" The Rockbox Crew