Monday, 06 July 2015 01:26

APRS iGate with the Radio Shield RS-UV3 Part 1

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Being an APRS enthusiast, when Curtis told me about the RS-UV3, I was really excited.  I already run an igate; KB1MTS.  However I was looking to add a second iGate for 145.825, keep costs low, and keep the foot print for the entire device really small (plus as a bonus, something to show at Dayton this year).  My current solution uses a Kenwood radio, a TNC-X, a USB adapter, and Beagle Bone Black which is a spaghetti mess of cables for data and power.  For my new iGate, I decided I wanted something that fit in a box, and only had a single power connection for everything.  This is Part 1 of a series about what I did for Dayton and has been in testing a compact and reliable solution.

 

 

A bunch of boards to connect...

On hand I already had a Raspberry Pi2 as well as a TNC-Pi that I could show for Dayton, but needed to find a way to hook it all together.  My first thought was to connect the PI2, TNC-Pi, and RS-UV3 with a Arduino to Pi adapter.  However from what we found, none of the adapters have any sort of voltage regulation to be able to plug it all together *and* power it. With limited time for Dayton, I elected to mount the boards side by side instead in the enclosure.  (If there's This email address is being protected from spambots. You need JavaScript enabled to view it., maybe we'll look at making a Pi to Arduino adapter with voltage regulation...)  My next realization was the existing TNC-Pi to use with the Raspberry Pi2 offsets a bit more than I liked for fitting into an enclosure.  I contacted John at Coastal Chipworks, and he was nice enough to send me a TNC-PI2.

Radio and TNC

John's TNC-Pi2 solved the board space dilemma, but not my power requirements:

Raspberry Pi2 5v
TNC-Pi2 5v (from the Pi)
RS-UV3 9.5v-15v

 I wanted to power the setup off of 12v (13.8v) like the rest of my shack, so the RS-UV3 was all set, but not the Pi2.  My solution was a USB power adapter I found on Amazon that could take 7v-23v and step it down to 5v needed by the Pi.  The one I decided to use wasn't overly expensive, and could handle 2 amps continuous without a problem. 

  • Input: DC 7-23V
  • Output: DC 5V
  • Output Current: 3A MAX
  • Continuous Long-time Operating Current: 2A
  • Reverse polarity protection

After running for a few days, It wasn't overly warm even under the heat shrink tubing, so figured I was in pretty good shape for now. (As a side note I took the box out of my attic to take pics after a couple months over over 110F temps, and see no signs of any problems after it's been running 24x7.)

I used an old power cable with a 2.1mm plug I had on hand, however you can buy one of these from HobbyPCB with a pig tail connector.  I wired this power connector in parallel with the USB power supply, and then connected them to an Anderson Powerpole connection for a single power connection.  

 

Power's great, but what about the audio?

For the audio I used these Radio connections on the TNC-Pi2:

  • Pin 1 (the square pad): Receive Audio
  • Pin 2: Ground TNC-Pi
  • Pin 3: TX Audio
  • Pin 4: Push to Talk (PTT)

...and connected those to the DB9 I/O connector pins on the prototype RS-UV3 board I had.  Luckily the blue production boards have SPKR, PTT and MIC pins that you can use, as well as a ground (each pin to the left of those is a ground pin.)

 

Last but not least the antenna and misc I/O connections

I picked up some SMA connectors on Amazon to run to a hole I drilled in the back of the enclosure (about the only thing that looks good on the back...)    I used a nibbler to cut the rest of the whole which as you can see did not go as well as planned as I'm horrible with the dreaded nibbler.  The USB connector I also sourced from Amazon as well as the Ethernet jack.  Both of those plug into the back of the Raspberry Pi 2 board.

 

Parts List

 

Part 2 will be how I configured the Linux and software on the PI.

 

Read 50235 times Last modified on Friday, 25 September 2015 18:26