My name is Ramiro and I’ve joined Balena two weeks ago. I’ve started now working on my residency project at balenaLabs after some research/experimentation about what to work on, and I wanted to share the project idea and use this thread to also track the progress I make.
I chose to work on something related to Software Defined Radio because I like a lot the things you can do with it, like a GPS received, AM/FM received, aircraft and ship tracker and much more! After playing with some ideas I’ve settled on one.
Wouldn’t it be great to have a Raspberry Pi based AM/FM/SW radio?
I could start with a Pi + a SDR dongle.
Then connect the Pi to a speaker → boom we have sound
I could add a rotary switch ( now that I know how they’re called ) to tune the radio and a potentiometer to control the volume
I have several options for displays:
A simple frequency display with a 7-segment LED
A graphical display that resembles an analog radio dial
I could have “radio preset” buttons
I could have a “tuning level” indicator if I somehow manage to detect how far from the signal the currently selected frequency is
I’m currently on the “design/experiment” phase, learning which tools I could use and making a plan for the next weeks.
The building blocks I have in mind are:
A Raspberry Pi (3B or 4)
An SDR dongle. I have a nice NooElec NESDR SMArt HF Bundle , but it should work with any. Note that for AM reception you need some add-ons like the “Ham It Up”
The RTL-SDR package and related projects
Hardware knobs, buttons, and a case to fit the components
Displays. Haven’t decided on which one(s) yet
The project will be made available as a Balena Hub app so that anyone can install it on their Pi.
On the next post I’ll write about related projects and references I’ve found.
Using a modified version of the rtl-sdr rtl_fm program to control the tuner
The app is “balenized”, and I’ve had success running on a Raspberry Pi 4. Will try on a balenaFin
I have a very crude app that I’m using to control the tuner. This will be replaced with the hardware control once I get a rotary knob and learn how to use it
This is the repo I’m using to keep track of the app, code and related references:
I have some issues to solve; see the box on the top right. I need to explore this option a little more. In the next post, I’ll post the alternative I’m working on.
Here’s the current alternative. It lets rtl_fm handle the data acquisition and demodulation, and it outputs an audio stream that can be piped to other applications. It uses a modified version ( called rtl_udp ) that provides a “command channel” similar to the one provided by rtl_tcp
Hi @mpous , great ideas. I was thinking on first creating some internal component for the rotary knob reader to keep the interfaces simple; I have to read a bit more about blocks but I think making a reusable block sounds great
And about the UI I was thinking of using a simple graphics display ( 240x180 or something like that ) because I wanted to do something at a lower level than a browser, but I’ll keep that in mind!
WAT!! A “Sound cabinet” Make the extra small model - Home This is excellent and beautiful, a cabinet where we can put the Pi. I could use this or an old radio. Or make two and use both!.
I’ve been working on implementing the following components:
rotary-reader: a node app that reads the input from a rotary knob via GPIO, calculates an abstract value from clicks it receives from the knob, and publish the new value by sending a UDP packet ( a very simple protocol )
radio-player: no updates for this one as it was working already. I’ve learned about an “absolute tuning” mode that I’m currently using ( more about this later )
display: I want to show at least the current frequency, as any regular radio does, so I’ve been working on creating a library or block that displays this info in a simple OLED 128 x 64 tiny screen
controller: a node.js app that syncs the different modules and provides feedback to the user
Here’s a video of the current prototype. The basic features are working!
It plays a radio, you can use the knob to change the frequency, and the radio provides some feedback using a display and two leads ( mainly used while debugging )
Meanwhile, I’m working on making a balena block out of the rotary reader component.
I’ve created a “proto-block” called rotary-reader that can be used to integrate a rotary encoder into an app without having to deal with GPIOs. The block integrates a couple of node.js libraries and sends the events to other containers using an UDP datagram. The code is at finradio/rotary-reader at main · ramirogm/finradio · GitHub . I built a couple of images and published them to Docker Hub Thanks @mpous for the idea! If anyone wants to take a look or give feedback go ahead
Here’s the diagram for the current version. I’ve added a Volume knob. I also got a set of tiny speakers that I plan to put inside a case to hide all the cabling
