[arm-allstar] HamVoIP I/O support - What is Best Current Practice for implementing I/O?

[Doug Crompton]

Randy,

  I have written a script to do exactly what you want to do using the Pi
I/O. I will dig it up tomorrow and pass it on.

Caveats - the pi is strictly 3V logic.  If the lines are TTL 5V logic then
the best thing to do would be to use Schottky diodes on each line similar
to how COS is done on the FOB. The Pi would pull the appropriate lines low
but would not see the 5V from the radio. Really a rather simple hardware
interface.

The channel is passed to the script via calls from rpt.conf functions so
DTMF would change the channel like -

1 - *801, 2 - *802, 3 - *803, etc.


*73 Doug*

*WA3DSP*

*http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*



On Fri, Jan 12, 2018 at 2:53 AM, "Randy Neals via arm-allstar" <
arm-allstar at hamvoip.org> wrote:

> Hi,
>
> What is the best current practice for implementing I/O on a Raspberry Pi to
> control external things.
> In this case, remote channel selection on a VHF remote base, a radio with 8
> channels and having external control lines.
>
> From looking through the list archives, I see references to using an
> Arduino Nano, and at an earlier time, using a USB I/O board from SparkFun,
> and of course using the lines on the RPi itself.
>
> Anticipated questions...
>
> Q. What Am I trying To Do?
> A. Control channel select lines on a VHF remote base station.
>
> Q. What format/How many lines?
> A. 3 logic control lines. The lines are normally pulled up to +5V by the
> radio.
>      BCD format with the lines having binary weighting of 4, 2, and 1
> respectively.
>      High = weighted value / Low = zero value.
>
> Q. What audio interface will I use?
> A. Simple USB, likely DMK URI. (But I could use a USB FOB, or other
> interface if there is one with I/O)
>
> Thanks,
> Randy
> W3RWN
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