Summary: For about $30 US, you can have a Raspberry Pi based EchoLink/SvxLink node. All it takes is a Raspberry Pi Zero, Zero 2, 3, etc. and and Pi Audio Hat. With a little more work, you can use an inexpensive USB Audio dongle for the audio interface.
I recently acquired some new Raspberry Pi Zero 2 (w) single board computer boards. The new Pi Zero 2 has a quad core Arm Cortex A53 running at 1-GHz with 512MB RAM – Amazing for such a small package!
The first thing I did was to download the newest version of the Raspbian Operating System, Raspbian GNU/Linux 11 (bullseye).
Next I installed a Pi Zero form factor audio hat from KeyeStudio called the “ReSpeaker 2-Mic Pi HAT V1.0 ” ($14 from Amazon)
I updated my djspot installer which uses the same audio codec for the new operating system. It’s available here: https://nj6n.com/svxlink/djspot_svxlink_bullseye
To use the ReSpeaker in place of a djspot RF board, you have to change the gpio configuration. In gpio.conf, remove the settings for gpio 13 and gpio 26 and add a new active LOW entry for gpio17. In svxlink.conf, change the [Rx1] GPIO setting to use gpio17 (the on board button) for SQL detection. Change the PTT_TYPE entry in [Tx1] to NONE.
Update “plughw:0” in both [Rx1] and [Tx1] sections to “plughw:1” because the PiZero 2’s HDMI audio interface is on “card 0”
Once you’ve done that, restart the system and you should have a working configuration.
To complete my project, I designed a 3D case that encloses the Pi Zero 2, provides a cutout for power and external speaker along with an extension for the on-board button used for PTT (actually COS).
My case is designed such that it can be affixed under one of my workbench shelves. The speaker will be mounted nearby and the PTT button can be easily accessed for transmitting. DTMF controls what the node is connected to – I play pre-recorded DTMF command sequences from my iPhone or Mac to connect to different talk groups or EchoLink nodes.
Update – I redesigned my case to make room for a 20mm loudspeaker. The audio is a bit on the anemic side, but I believe it will work fine. This is now a self-contained svxLink node using inexpensive parts that are readily available.
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