Radiation King Radio:

A pygame based music player with many unique radio band and live playback features. This was designed to run on a Raspberry Pi Zero along with other off the shelf boards, but could be adapted to other hardware.

This is a work in progress. See the project log.

Features:

• Simulated live radio station playback
• Time synchronized playback of real world stations
• Multiple virtual radio frequency bands
• Noise, fuzz and other tuning sounds effects
• Automatic parsing of folders and audio files
• Automatic distribution of radio stations across an analog dial
• Cached song metadata for faster handling of large libraries
• Analog Air Core Motor control
• Switched potentiometer based volume and tuning inputs
• Manual button activated tuning
• Manual song skipping
• Fast-forward, rewind and pause (including time shifting)
• Playback ordered or randomized stations
• Ultrasonic Remote Control Support (Disabled by default)
• Standby mode
• Neopixel light control with warm start/shutdown effect
• Stereo playback

#Licence: Licence: Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)

Audio Folders:

Audio Files:

The software will only search for .OGG audio files. The OGG format was selected to make the metadata processing optimized, as well as take up less CPU.

I recommend using Foobar2000 along with oggenc2.exe as you can also normalize your files at conversion time. First scan your library to apply Replaygain tags. Then convert the files using Foobar2000's convert command to apply Replaygain offset to the files while also converting them to .OGG I used the "apply gain without clipping" option.

Band Folders:

The first folder level under "radio" are the "radio band" folders. Think of this like sort of like AM, FM, Shortwave, etc... It works out best to use the bands for things like "Fallout 4 stations", "Fallout Mod Stations", "Holiday Stations", etc... Prefix the name of the folders with 00, 01, 02, etc... to set the order of the radio bands. Example folders have been included.

Station Folders:

Inside each radio band folder you will place sub-folders with audio files inside. Each sub-folder will become a "Radio Station" See the "ZZ_test_stations" folder for an example. There must be at least two radio stations inside a radio band folder.

Prefixing the names of the radio station folders with 00, 01, 02, etc... will set the order on the dial. Similar prefix naming of song files is required for ordered file playback.

The software will automatically spread the stations evenly across the dial. The amount of stations that can practically fit will depend on how far your dial can turn. For example the dial on my design can move 150 degrees. So if there are 10 radio stations they will end up about 15 degrees apart on the dial.

station.ini files:

Each radio station folder should have a file named "station.ini". This contains the radio station name, as well as whether the radio station should have ordered or random playback.

If the file is missing it will be created upon cache generation. The below data is required if you want ordered playback. A [cache] section will be added to each station.ini file to save the metadata for each song. You should delete the [cache] section in the station.ini file in any folder in which you have changed files or moved.

The start_time is the time seconds since midnight local time. 21600 seconds would be 6 am for example. 0 is a midnight start time. This is useful for making a station out of real world broadcast recording such as https://archive.org/details/CompleteBroadcastDay This is an offset applied to allow for virtual real-time syncing.

Example: [metadata] station_name = The Shadow ordered = True start_time = 0 E #Software setup:

Requirements:

Make sure and install all the requirements listed in requirements.txt on your Pi Zero. CircuitPython 7.3.3 must be loaded onto your Pi Pico.

settings.py file:

This is a file that has settings you may want to tweak. Such as the volume of the static background sounds, and whether to re-build all the cache files. You should disable the cache setting after a full scan to prevent it from repeating upon the next boot. Individual folders will be scanned if their Ini file is missing the Cache section.

Pi Pico files:

The pi_pico_files folder contains the code for the Pi Pico. You must have already loaded CircuitPython on the Pico prior to connecting the Pi Pico to the Pi Zero over USB. The Pi Zero code will automatically mount and copy the files needed to the Pi Pico. The code is designed to allow the Pi Pico to communicate over USB UART. Two boot cycles of the Pico may be needed for the setting to take effect. The "pico_settings.py" file has options you may want to tweak related to the buttons, motor control and other settings.

Auto running the script:

• Run sudo raspi-config on the Pi Zero. Select “Boot Options” then “Desktop/CLI” then “Console Autologin”
• Ensure the files are in \home\pi\radking
• Run sudo nano /etc/profile
• Add to the file:
  • cd /
  • cd /home/pi/radking
  • sudo /usr/bin/python -u /home/pi/radking/main.py &

Note that this method runs the script anytime any console connects, be careful to stop the script on one console before running another.

Operation:

How the "Live" playback works:

Each radio station is basically a playlist of audio files, with the duration of each music file. Using a deque list allows the list to be looped with the top item being moved automatically to the bottom of the list.

When the radio starts up: It saves the previous midnight time as the "master_start_time". Each radio station uses this as reference when the station is selected. When you tune into a station some amount of time has passed since the master start time. The code checks the first song on the list. If the song is shorter than the time that has past: It moves it to the bottom of the list, and the length of that song is also removed from the past duration. This repeats until the current song at the top of the list is longer than the remaining time. The code then jumps into the song at the remaining time.

By using this method, each station acts as if it is playing back live. You can tune off of a station and go back and have it resume at the correct time. The deque list has the advantage that we don't have to keep track of a current song index, and we can easily randomize, skip/rewind or pause playback without losing the live playback effect.

You can even fast-forward, rewind, skip or randomized the songs all without losing the live effect. Manually randomizing an ordered station can't be restored without a reboot.

Analog Controls:

The volume knob/switch controls the audio volume as well as turning the radio on/standby. The tuning knob controls the angle of the motor and therefore the radio station selection. By turning off the tuning knob: You can then use the volume knob to control the neopixel brightness. The software automatically calibrates the potentiometers at boot time to their min/max values. This causes some odd action at boot, but once the pots are fully cycled everything should work correctly.

Buttons:

The five buttons below the dial have the following functions:

1. Press: Rewind, Hold: Previous song
2. Press: Previous band, Hold: Previous Station
3. Press: Play/Pause (Without standby), Hold: Randomize station
4. Press: Next band, Hold: Next Station
5. Press: Fast Forward, Hold: Next Song The button functions can be altered in the Pi Pico code.

Motor angle feedback loop:

Each radio station is assigned an angle on the radio dial as a sort of angular address. When you move the tuning knob, the code moves the motor to a certain angle. Then it checks to see if there is a radio station near, or at that angle.

By doing this in a feedback loop you don't have to worry about the exact positions of any single station, and it automatically adjusts to frequency bands with different numbers of stations.

The code automatically determines how precise the angle needs to be to allow for a lock on zone around each station. If you are near a station it will play back the station at a lower volume, with static noise at the same time. The volume of the station rises as you get near it, and plays in the clear once you hit the lock on zone. There is also an area with just static noise between each station.

If you cram too many stations into a single band, there may be no empty space between stations and precise tuning will become difficult.

##Sweep effect: The software has a band sweeping effect that plays when a band is changed, or the radio is turned on. This effect provides a soft start, as well as a preview of each station as the needle sweeps across the band. This can be disabled in the zero settings file, or the speed altered in the pi pico settings file. Note that if the speed is too fast the station preview effect will lag behind the needle movement.

#Hardware: The radio uses a Pi Zero W and a Pi Pico together. The Pi Zero provides the fast music access and playback, and the Pi Pico handles all the analog and GPIO. A USB cable is required between the Pi Zero and Pi Pico. UART over USB is used for each of the two devices to talk to each other.

To debug the Pico on the Pi Zero run: "minicom -b 115200 -o -D /dev/ttyACM0" on the Pi Zero.

An Adafruit Speaker Bonnet, or any other i2s audio device can be used for the speakers. This is connected to the Pi Zero.

##Air Core Motor: A TB6622 Dual-H Bridge motor controller is connected to the Pi Pico and handles the Air core motor. I found this specific Dual-H bride driver is required for an air-core motor. It has the separate PWM and direction controls needed.

Air-Core motors are better for analog dials then stepper motors. A stepper motor has only a fixed number of steps. I found the stepper movement to look robotic even when using half steps. An air core motor however is purely analog and can smoothly move to any angle needed.

##Potentiometer control: I opted to use Potentiometers instead of rotary encoders for a similar reason to the air core motor. They are just more analog feeling. You should use a switched logarithmic "Audio" pot for the volume control, and a linear pot for the tuning control. If you use a linear pot for both, adding a 680ohm resistor to one the ground legs of a 10k linear pot can somewhat emulate a log pot. Use a switched pot for the tuning control also if you want to disable the knob for manual/digital turning.

##Neopixels: An array of 8 Neopixels are used to light up the gauge display. As you change bands, one LED will light up briefly to indicate which band number you are on.

##Ultra Sonic Remote: Using a SPH0641LU4H-1 Mems Microphone, and PWM audio a 1950's mechanical remote can be setup to operate the radio. A high pass filter is applied to the audio prevent the music from interfering with the remote control. A FFT of the ultrasonic samples is performed. The index of the highest peak determines which button has been pressed.

#Band Callouts: Inside each band fold you can place a "callout.ogg" file. This will optionally (see settings) playback the file each time you change radio bands. I created my callout file by using voicemaker.in, Matthew Englis at -15% speed. I have found this voice is very closer fo the storyteller's voice.