[App_rpt-users] USB FOB pin 13 (PTT)

[Andrew Errington]

On Mon, December 5, 2011 09:23, Larry wrote:
> A Newbie here with a problem.
>
>
> I'm still trying to grasp the ins and out of Astrisk and App-rpt etc.
>
>
> I'm trying to connect a USB FOB to my RC-210. I do grasp the reverse
> RC-210 wiring process. However I found no way to force pin 13 high to
> activate PTT pin from the FOB for testing purposes.
>
> Any suggestions on how or if I'm doing something wrong?
>
>
> I have added a PTT LED for monitoring the output logic from pin 13 but
> have never been able to get it to turn with any function I've tried other
> than forcing a voltage at the junction feeding it and the base resistor of
> the 2N4401.  My RC-210 will work at that point but I'm not certain if I
> have an issue with the USB FOB PTT output.
>
> Am I am missing something or perhaps I don't understand the logic of the
> different functions.
>
> I'm not against reading but jumping all around to find different
> materials has left the mind in a jumble.  Can anyone enlighten me as to
> when in the sequence PTT output becomes active and the voltage I should
> find on that pin when it does?

Hi,

I don't know about app_rpt, but I have played a bit with USB audio devices.

What is the model number of the USB audio chip on your audio fob?  If you
can't read it, then please report what is the USB vendor ID and product ID
for the device (you can see this appear in /var/log/messages when you plug
the USB device in)?

How it's supposed to work is this:
The GPIO pin (let's say it's pin 13) will be low when the software doesn't
need to transmit.  When the software wants to transmit, it will drive the
GPIO high (which will turn on the NPN transistor that drives PTT).  The
software will wait for a short time to allow the radio to key up, then it
will drive an audio signal for the data to be transmitted on to the audio
output of the device (which is hooked up to the audio input of the radio).
 When the audio data is finished the software will wait for another short
time then de-assert the GPIO which will turn off PTT.

If you are having trouble you could try the latest version of Thomas
Sailer's soundmodem.  I added support for USB-controlled PTT.  You could
compile the code and configure soundmodem for your USB device then use the
soundmodem test software to turn PTT on and off.  I also wrote an
extremely poor piece of software that dumps HID control packets to the
device to drive the GPIO lines.  Basically you write HID data to
/dev/hidrawX

73,

Andrew
ZL3AME