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Subject: Re: Still Problems with AJB Remote
From: sophana (jobarjo78_at_yahoo.fr)
Date: 2004-07-16


[IDC]Dragon wrote:

>>Sophana told me once to simply use a 10k resistor and connect it directly
>>from my uC's UART pin to the JB's remote pin.
>>
>>
>
>I can't recommend that, because it weakens your ability to pull the pin low.
>The Archos has an internal pull-up on the remote input, which I have seen
>being either 1 kOhm or 10 kOhm.
>If you use the pin just as an input (not bi-directional), I'd recommend to
>use a schottky diode to "emulate" an open collector. The diode will allow
>your Atmel to pull the pin low, current flowing out of the remote pin. But
>it will prevent your Atmel from driving it high up to the 5V level. Instead,
>the internal pullup will take care of the signal going up again.
>
>
>
Hmm, I didn't know there were an internal pull up.
In this case you are right, the low offset (schottky) diode is the best
solution. (although I don't know a wide schootky diode reference like
1n4148)
If you don't have a schottky, a 1n4148 could work but you will be near
the voltage limit.

>>Does anybody know, what are the differences of the remote input circuit
>>inside the Studio Player's, old Recorder's and newer Recorder's (like V2)
>>?
>>
>>
>
>Thare should be none, except for the strenght of the pullup.
>
>
>
>>Maybe anybody has a schematic ?
>>
>>
>
>See the ducumentation pages.
>
>
>
>>Does anybody know a universal circuit to drive the remote pin, that works
>>with ALL models ?
>>
>>
>
>The universal bidirectional solution is that circuit with a MOSFET
>inbetween, preventing the voltage to rise above 3.3V. I once posted that, am
>too lazy to dig it out right now.
>
>
>
the mosfet will not do the open collector behaviour. It is indeed
usefull for adapting the voltage for a bidir pin. But his uart Tx pin is
not bidir.

>Jörg
>
>
>

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