Category: Streaming

Instead of adapting an existing Internet Radio project to my needs (like support for air traffic control stations), I decided that it would be easier to write my own sketch from scratch. I’m satisfied with the first results, and I learned a lot from this project.

Keypad controlled prototype in radio mode (left) and ATC mode (right)

The radio runs without problems on a Wemos D1 R2, driving an Adafruit VS1053 breakout and a 2.4″ ili9341 TFT display. It can be controlled with a 16-key matrix keypad (the pictures show a Wemos D1 Mini Pro, but its wifi turned out to be too slow for some stations).

The prototype uses almost 500 lines of code for the radio. David Bird’s excellent METAR functions take yet another 500 lines. Too big to post on this page, I’m afraid…

It has the following features (more will be added later):

• Can play mp3 encoded streams from internet radio stations (up to 320 Kbps).
• Controlled by means of a 4×4 matrix keypad, using VS1053’s own GPIO pins.
• Offers storage of 40 station presets (grouped in four  bands).
• Displays station name and song title on a TFT display.
• Displays a decoded weather report (METAR) when playing an air traffic control (ATC) channel. The first 10 stations in the preset list are reserved for ATC stations (I used David Bird’s excellent functions for METAR decoding).
• A 30 Kbyte ring buffer is used for smooth playback.
• Designed to handle chunked transfer encoded streams if necessary (I was unable to test this, because I couldn’t find any station that uses this encoding).
• Stereo dB levels can be read directly from the chip and be used to drive VU meters from PWM pins.

Below is a flow chart of the initial connection, followed by the streaming process (basically a finite state machine). In practice, it all comes down to determining each incoming byte’s function within the stream by keeping track of some counters and states. Once the actual streaming has started, an incoming byte can be one of the next types:

1. audio byte – will be sent to a ringbuffer that feeds the VS1053 decoder
2. metadata byte – a human readable character from the song title
3. metadata size – an integer; multiplied by 16, it is the following song title’s length
4. CR or LF – used as separators
5. chunk size (if station uses chunked transfer encoding) – size of the next chunk

While still in an early stage of research for my Internet Radio (previous post), I came across Ed Smallenburg’s comprehensive Esp-radio project on github. It’s a very well documented project with a heavily commented sketch.

Instead of proceeding with my own (basic) Internet radio project, I decided to take Ed’s nearly flawless Esp-radio as a starting point, and adapt it according to my personal needs. Most important change will be the addition of two small oled displays for emulating analog VU meters.

There’s also an (even better?) version for ESP32 by the same author. This persuaded me to finally enter the ESP32 world, so now I’m the proud owner of a Wemos LOLIN32 Pro. My hope is that this powerful dual core board will be able to drive the entire setup of radio, TFT touch display, IR remote and VU meter oleds.

Update:

Unfortunately, my Wemos LOLIN32 Pro is from a batch with a faulty serial chip (CP2104). Most of the time, my PC will not recognize the board when I connect it, resulting in the serial chip becoming very hot within 5 seconds. This is my fourth Wemos device, two of which were crap!

However, when the board is recognized, it works fine and I even managed to upload and run the ESP32-Radio sketch. As for performance, I would say that both versions (ESP8266 and ESP32) seem equally satisfying and stable.

Below is a screenshot of the web interface. I removed and changed some buttons from the original version, and added a “now playing” display that updates every two seconds.

My futher plans with an ESP32 based Internet radio will have to wait for the replacement of my board. Planned changes are mainly peripheral and cosmetic, like adding VU-meters and a frequency analyzer. To be continued (stay tuned…)