[arm-allstar] FOB Interfacing

[Doug Crompton]

Just a heads up as from time to time this subject comes up and with many
new people on this forum and growing I want to point out a few things.

Our main means of audio and GPIO interface to Allstar is the USB FOB. Since
historical problems seem to propagate forward and never go away I want to
make it clear that the USB of 2018 in Linux is NOT the USB of 2009. That is
it is mature and stable and the current FOBS we have work well. None of the
earlier (5+) years ago problems exist today.

The scare about "Blobed" USB FOB's we had a year or two ago no longer
exists. There is ample supply of Chinese FOB's at $2-3 each available that
can be modified. See the links at hamvoip.org. There are also many sources
of FOBS specifically for Allstar out there and more coming.

If you want to modify your own FOB there are instructions on how to do so
on the hamvoip.org web page. This is obviously optional and if you have the
ability to do that then go for it. It is really not difficult for those who
build and modify things. If not select one of the currently available
commercial FOB's.

The fantasy that using Pi GPIO for controlling PTT and COS would be super
easy is just that, a fallacy. You still would have to be able to build the
required interface circuitry and run wires from the Pi to the radio. This
would result in a much more kludgey installation and could result in RF
issues both into and out of the Pi. It also would mean that the Pi could be
exposed to outside transients and possible damage. The Pi is strictly 3.3
volt GPIO and anything higher will cause it to fail so if you are using it
to do long lead GPIO it would be best to use interface chips again making
the whole process more complicated.

GPIO on the FOB's works well and with the CM119 chips offers 7 additional
bits of I/O for your use. Many use these bits for channel steering, fan
control, and other control projects.


*73 Doug*

*WA3DSP*

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