Re: A Simple Portable Packet Station for Emergency Communications


David Ranch <dranch@...>
 


Hello RIchard,

Your solution seems overly complex but maybe I'm missing something:

   - Why use a relay with a higher delay time compared to just using a simple transistor circuit with lower delays?

   - Why do all the complex tapping into the onboard output-only soundcard when you still need a soundcard input?  Why not just do everything on the external sound device (input and output)?

--David


On 06/20/2019 08:04 AM, Richard Bates wrote:
On Wed, Jun 19, 2019 at 08:18 PM, Guillermo/Bill wrote:
Could you expand on the PTT part a little bit?
The DireWolf manual,  section 9.2.8.3, page 66, explains the addition you need in the direwolf.conf file, for example to use GPIO 26 you want

PTT GPIO 26

i.e. in this example, GPIO26 (pin #37) will go "high" when the software TNC wants to transmit.

This small reed relay fits conveniently inside the RPi case, and can be soldered directly to to GPIO line.

You can see that:
 - relay pin 1 connects to the radio PTT line
 - relay pin 2 connects to the GPIO line, pin 37 in this example
 - relay pins 3 and 4 connect to ground, for example pin 39

As I didn't need the functionality of the built-in RPi audio, I choose to disconnect the RPi audio-out lines from the built-in mini-jack, by breaking the tracks - so I could use it for the PTT line (relay pin 1).


You could alternatively simply add a mini-jack to the RPi case and take the PTT signal out that way.

Richard

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