[Linux-ham] soundmodem

[donroden at hiwaay.net]

Think you will need an op-amp to correctly ( reliably ) change the levels.

Don W4DNR


Quoting folkert <folkert at vanheusden.com>:

> Hi,
>
> I'm planning on building a soundmodem setup with my raspberry pi.
> At http://i.stack.imgur.com/Y2J1W.gif there's a schema for creating a
> PTT switch with a real serial port. The RPI does not have RTS/CTS but
> tons of GPIO pins. Now GPIO pins work with 3,3v and RS232 is at 12v so I
> think I need to increase the 10k Ohm resistor? Or decrease it? Probably
> decrease it as (guessing here) the 10k was there to reduce the voltage
> on the trigger-pin of the transistor? Any help is appreciated.
>
>
> regards,
>
> Folkert van Heusden
>
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