Pi Node-Red Internet Radio

Node-Red is graphical programming interface that allows logic to be created using nodes that are wired together. Node-Red has been pre-installed in the Raspian OS since 2015 and it has a very easy learning curve.

In this blog I wanted to show an example of Node-Red being used with a five button LCD faceplate to play Internet radio stations.

For this project I used a basic USB powered speaker and a Raspberry Pi 5-button LCD faceplate. The cost of the faceplates start at about $10.

Getting Started with Internet Radio

There are a good number of Internet radio resources, https://www.internet-radio.com has a good selection of stations to choose from.

To find a URL of a radio station, look through the stations until you find what you like and then right click on the .pls link, and “Save Link as…”. Save this link as a file and then open the file in a text editor to get the URL.

radio_stations

 

MPD – Music Player Daemon

MPD is a Linux based music service that supports the playing of both music files and internet based radio stations. For command line operations that is also a MPD client application called mpc. To install both the service and client:

sudo apt-get install mpd mpc

Before I started building the node-red application I played with the mpc commands to ensure that I understood the basics.

Internet radio stations are added like a song list:

mpc add 'http://uk2.internet-radio.com:8062'
mpc add 'http://live.leanstream.co/CKNXFM'
mpc add 'http://66.85.88.2:7136'

Some key mpc control commands are:

mpc play  # play the current station
mpc play 3 # play radio station 3
mpc pause  # pause the music
mpc next  # play the next radio station
mpc prev  # play the previous radio station 

mpc volume 90 # set the volume to 90%
mpc volume +5 # increase the volume 5%
mpc volume -5 # decrease the volume 5%

The mpc status command will show the volume, what is playing along with the current station number and total number of stations:

$ mpc status
Comedy104 - A Star104.net Station: Doug Stanhope - To Tell You the Truth
[playing] #2/4 1:45/0:00 (0%)
volume: 75% repeat: off random: off single: off consume: off

Node-Red Logic

Node-Red can be started from the Raspberry Pi menus, or from the command line:

node-red-start &

To access the Node-Red web page, enter the Raspberry Pi ip address with port 1880, for example : http://192.168.0.121:1880

For this project two extra Node-Red components are needed, and they are for the LCD faceplate and the MPD music player. To add components use the “Palette Manager” option.

palette

For the LCD faceplate, search for Adafruit, and select the i2c-lcd-adafruit-sainsmart component.

adafruit_palette

Similarly search for mpd and add the node-red-contrib-mpd component.

mpd_palette To create logic select a node from the left node panel and drag it onto the center flow palette, and then “wire” the nodes together.

For the Internet music example I used four function nodes, and the two i2cLED and the two MPD nodes. (Comment nodes are only used to explain the logic).

node_red_radio

The first step is to double click on the MPD nodes and add an MPD server.

Select Button Logic

I used the select button to turn on and off the music player.

A context variable is created to save the current state of the player. Note: a context variable is only accessible for the node where it is defined..

The ic2_LCD_Input node message has a msg.button_name and msg.button_state item that is used to determine which button is pushed.

For the select button logic a group of messages was used to add the different radio stations.


// create an "is setup" variable
var issetup = context.get('issetup')||0;

if ((msg.button_name == "SELECT") && (msg.button_state == "pressed" )){
// if the setup hasn't been run, add a radio station playlist
if (issetup === 0) {
context.set('issetup',1);
var msg0 = { payload:"clear"};
var msg1 = { payload:"add http://185.33.21.112:11029" }; // 1.FM Trance
var msg2 = { payload:"add http://66.85.88.2:7136" }; // Comedy 104
var msg3 = { payload:"add http://live.leanstream.co/CKNXFM"}; // The One - Wingham
var msg4 = { payload:"add http://185.33.21.112:11269" }; // Baroque
var msg5 = { payload:"play" };
return [ [ msg0, msg1, msg2, msg3, msg4, msg5] ];
} else {
context.set('issetup',0);
msg0 = { payload:"pause"};
return msg0;
}
}

Up/Down Button Logic

The UP button will issue an MPD command equivalent to :

mpc volume +5

This will up the volume by 5%. The total volume will max at 100%.

The DOWN button will issue an MPD command equivalent to :

mpc volume -5

// Raise/Lower the volume
var msg1;
var thevolume = 5; //volume % increment to change

if ((msg.button_name == "UP") && (msg.button_state == "pressed" )){
// if the setup hasn't been run, add a radio station playlist
msg1 = { payload:"volume +" + thevolume };
return msg1;
}
if ((msg.button_name == "DOWN") && (msg.button_state == "pressed" )){
// if the setup hasn't been run, add a radio station playlist
msg1 = { payload:"volume -" + thevolume};
return msg1;
}

Current and Max Radio Station Logic

The ‘Current and Max Radio Stations’ node is updated from the MPD in node when there are any changes to the volume or when a new song or station is played.

This logic creates two flow variables (stnmax, stncnt) that are available in any node in this flow.  The station max (stnmax) and current radio station (stncnt) variables are used in the LEFT/RIGHT button logic to determine which station to change to.


// Get the max number of radio stations and the current radio statio
// Make context variables that can be used in other node, like the LEFT/RIGHT button

var msg1 = msg.payload.status ; //create a simplier message
var stnmax = msg1.playlistlength;
flow.set('stnmax',stnmax);
var stncur = msg1.nextsong;
if (isNaN(stncur)) {stncur = stnmax;} // ensure a valid station

flow.set('stncur',stncur);

return msg1; // only needed for possible debugging

While the code is running it is possible to view the context date.

context_flow

UP/DOWN Button Logic

The UP / DOWN logic changes between the radio stations using the mpc commands:

mpc next
mpc prev

It is important to not move past the range of the radio stations or MPD will hang. The stnmax and stncur variables are used to determine if the next or previous commands are to be allowed.


// Move left and right in radion stations
var stnmax = flow.get('stnmax');
var stncur = flow.get('stncur');
if ((msg.button_name == "LEFT") && (msg.button_state == "pressed" )){
// if the setup hasn't been run, add a radio station playlist
if (stncur > 1) {
var msg0 = {payload:"previous"};
return msg0;
}
}
if ((msg.button_name == "RIGHT") && (msg.button_state == "pressed" )){
// if the setup hasn't been run, add a radio station playlist
if (stncur < stnmax)
var msg1 = {payload:"next"};
return msg1;

}

Final Comments

The Pi LCD faceplate is an excellent hardware add-on for any Raspberry Pi project. However it important to know that clone hardware may work as expected. For my hardware I was not able to easily turn off the extra LED.

A future enhancement would be to add a Web interface so that you could change the volume or stations without using the 5 button Pi faceplate.

 

Gesture Controlled Radio

Our goal was to make an kitchen Internet radio player where we could change the volume and stations without touching the player. For this project we used:

  • Raspberry Pi 3 (or 2 with a Wifi dongle)
  • Pimoroni SkyWriter (~$20US)
  • USB powered portable speaker

The Pimoroni SkyWriter supports both gesture and touch control.

Setup

To install the Pimoroni SkyWriter python libraries:

curl -sS get.pimoroni.com/skywriter | bash

For the internet music interface we used the mpd , Music Player Daemon, it can be installed by:

sudo apt-get install mpd mpc

The SkyWriter can be wrapped in plastic wrap and the gestures can still be picked up. For a more robust project it would probably be best to design a more waterproof enclosure.

Python Code

A few years ago we found that the mpc calls were bullet-proof, but when we did this project we found that the mpd service would often lock up  if a new internet radio station was selected (mpc next). For this reason we used external calls to adjust the volume and we restarted the mpd service when we changed radio stations

We used a gesture of up/down to adjust the volume, and a left/right to change the station.

OLYMPUS DIGITAL CAMERA

Below is our final code:

#!/usr/bin/env python
import skywriter
import signal
import os

thevolume = 70 #starting volume
thestation = 1 #starting station

# Some internet radio stations
stations = (('http://185.33.21.112:11029','1.FM Amsterdam Trance Radio'),
            ('http://www.partyviberadio.com:8000','Raggae Roots'),
            ('http://66.85.88.2:7136','Comedy 104'),
            ('http://eu.radioboss.fm:8121','Yoga'),
            ('http://185.33.21.112:11269','Baroque'))

def setvolume(voldif):
  global thevolume
  if (thevolume + voldif >= 0) and (thevolume + voldif 0) and (direction + thestation <= len(stations))):
    thestation = thestation + direction
    os.system('mpc clear')
    os.system('sudo service mpd restart')
    os.system('mpc add ' + stations[thestation][0] )
    os.system('mpc play')
    print thestation, stations[thestation][0], stations[thestation][1]

@skywriter.flick()
def flick(start,finish):
  print('Got a flick!', start, finish)
  if (finish == 'north'):
    setvolume(5)
  if (finish == 'south'):
    setvolume(-5)
  if (finish == 'west'):
    newstation(-1)
  if (finish == 'east'):
    newstation(1)

# start playing the radio at defaults
setvolume(0)
newstation(0)

signal.pause() # wait for a new gesture

Pi FM Radio

There are few options for FM radio projects on the Pi, such as the RDA5807M and TEA5767 chips. We’ve built an Arduino FM radio using the RDA5807M chips but we found the documentation to be quite weak. There are some Python libraries for TEA5767 chips, unfortunately however you have no volume control with this chip.

RTL-SDR is a software defined radio (SDR) that uses a DVB-T TV tuner dongle based on the RTL2832U chipset. RTL-SDR dongles are well priced at $10-$15 and they are easy to use for Pi FM radio projects. Software Defined Radios have a large list applications that can done, some of the cooler projects include: tracking airplanes and ships, free-to-air TV, and monitoring satellite data.

Getting Started

For setup an external speaker is required (powered speakers work the best). The RTL-SDR dongle includes an externally connected antenna, if possible try to place the antenna close to a window.

fm_setup

To install the basic software enter:


sudo apt-get install rtl-sdr

The rtl_fm utility is an FM demodulator that is used to read and sample a selected frequency. The output of rtl_fm needs to be directed to an audio player program such as aplay. There are a few sampling and buffering options that must be defined. The syntax with the required options to play an FM radio station at 107.9 MHz is:

rtl_fm -f 107.9e6 -M wbfm -s 200000 -r 48000 | aplay -r 48k -f S16_LE

The rtl_fm application needs to be stopped when a new radio station is selected. If the rtl_fm is running in the background the ps command can be used to find process IDs. The kill command can then be used to terminate the task. An example to find and terminate the rtl_fm task:

pi@raspberrypi:~ $ ps -e | grep rtl_fm
1709 pts/0 00:00:33 rtl_fm
pi@raspberrypi:~ $ kill 1709
pi@raspberrypi:~ $ ps -e | grep rtl_fm
pi@raspberrypi:~ $

Adjusting the Volume

Typically the audio would be from an external speaker rather than the HDMI connection. To force the audio connection, use raspi-config and select the “Advanced” menu option, then selection “Audio”.

advanced

There are a few ways to adjust the volume on the audio. One method is to use the amixer utility. An example to change the radio volume to 70%:

amixer sset "PCM" 70%

A Python Example

For our basic testing we created a simple Python command line application. This application accepts new FM radio frequencies and volume settings. When a new radio frequency is selected the rtl_fm task needs to be stopped and restarted.

This application used a few Python libraries. The os library has the os.system call to shell out to external programs like amixer. The os.kill call terminates processes with a give process ID. The subprocess library has the call:

# simple PI FM radio utility using a RTL SDR dongle 

import subprocess, signal, os

def newstation(station):
    global process, stnum
      
    part1 = "rtl_fm -f " 
    part2 = "e6 -M wbfm -s 200000 -r 48000 | aplay -r 48k -f S16_LE"
    cmd = part1 + station + part2
    
    print 'Playing station :', station 

    # kill the old fm connection
    if process != 0:
        process = int(subprocess.check_output(["pidof","rtl_fm"] ))
        print "Process pid = ", process
        os.kill(process,signal.SIGINT) 

    # start the new fm connection
    print cmd
    process = subprocess.Popen(cmd, shell=True)


def setvolume(thevolume):

    os.system('amixer sset "PCM" ' + thevolume)
    print 'volume = ' , thevolume


process = 0

while True:
    answer = raw_input("Enter a radio station (i.e. 107.9) or volume (i.e. 50%): ")

    if answer.find('%') > 0:  
        setvolume(answer)
    else: 
        newstation(answer)                      

Summary

After the command line FM radio is working, it is possible to create standalone PI radio projects that use pushbuttons, TV remotes or Wii controllers to adjust the volume and stations. We built some projects using PiFace and LCD button shields.

The LCD Python code is below:

#!/usr/bin/python
# Pi FM Radio using an LCD Shield for controlling the stations and volume 

import os, subprocess, signal
import time
import Adafruit_CharLCD as LCD


def newstation(direction):
        global stnum, stations, process

        print 'stnum=',stnum,'direction=',direction              
          
        part1 = "rtl_fm -f " 
        part2 = " -M wbfm -s 200000 -r 48000 | aplay -r 48k -f S16_LE"

        if (stnum + direction  -1):
                stnum = stnum + direction
                print('Playing station :', stations[stnum]) 
                cmd = part1 + stations[stnum] + part2
                if process != 0:
                        process = int(subprocess.check_output(["pidof","rtl_fm"] ))
                        print "Process pid = ", process
                        os.kill(process,signal.SIGINT) 
                # start the new fm connection
                print cmd
                process = subprocess.Popen(cmd, shell=True)
            


def setvolume(voldif):
        global thevolume
        if (thevolume + voldif > 0) and (thevolume + voldif <100):
                thevolume = thevolume + voldif
                os.system('amixer sset "PCM" ' + str(thevolume) + '%')
                print 'volume = ' , thevolume
                

lcd = LCD.Adafruit_CharLCDPlate()
lcd.set_color(0,0,0)

## Add your own stations and station info
stations = ['95.3e6','94.7e6','102.9e6','107.9e6']
sinfo = ['95.3 country', '94.7 light','102.9 easy','Y108 Rock\nHamilton ']
thevolume = 40

stnum = 1               #pick a starting station
process = 0
newstation(0)
lcd.message(sinfo[stnum])
setvolume(thevolume)


print 'Press Ctrl-C to quit.'
while True:
        if lcd.is_pressed(LCD.UP):
                setvolume(5)
                time.sleep(0.25)
        if lcd.is_pressed(LCD.DOWN):
                setvolume(-5)
                time.sleep(0.25)
        if lcd.is_pressed(LCD.LEFT):
                newstation(-1)
                lcd.clear()
                lcd.message(sinfo[stnum])
                time.sleep(0.25)
        if lcd.is_pressed(LCD.RIGHT):
                newstation(1)
                lcd.clear()
                lcd.message(sinfo[stnum])
                time.sleep(0.25)   

littleBits/Pi Internet Radio

The littleBits Proto bit allows littleBits components to be directly to connected to a Raspberry Pi (or Arduino).

The Goal

The goal of this project was to play Internet Radio and use littleBits to:

  • start the music, (and possibily change the music)
  • control the volume
  • use the littleBits speaker

For this project we used:

  • 2 Proto Bits
  • 1 Fork Bit
  • 1 Button Bit
  • 1 Slide Dimmer Bit
  • 1 Speaker Bit
  • 1 Bargraph Bit (optional)
  • 1 Wire Bit (optional)

The Wiring

music_setup

For the littleBits to Pi wiring, the input to the Fork Bit needs to have 5V on both the power and data pins, the GND pin of the Proto Bit is wired to GND on the Pi.

music_circuit

The output on the littleBits Button bit is wired into GPIO 23 on the Pi.

The Logic

For the logic we used Node-Red, Python would have probably been a better choice, but we wanted to see if it could improve our Node-Red skills.

To play Internet music we need to load the Node-Red mpd node:

cd $HOME/.node-red
npm install node-red-contrib-mpd

The Node-Red logic used only 3 nodes:

  • 1 – Raspberry Pi input node, to read button push
  • 1 – Function node, to do some action on the button push
  • 1 – MPD Output node, to play Internet Radio

radio_logic

There are a lot of possible options for what the littleBits button could do. For this example we simply wanted to load an Internet Radio URL, and then start playing. To find Internet Radio stations go to: https://www.internet-radio.com/.

music_func

The function node had a context variable, issetup,  that was used to load the music for the first time and then start playing.

// create an "is setup" variable
var issetup = context.get('issetup')||0;

if (msg.payload == "1") {
// if the setup hasn't been run, add a radio station playlist
if (issetup === 0) {
context.set('issetup',1);
var msg0 = { payload:"clear"};
var msg1 = { payload:"add http://185.33.21.112:11029" };
var msg2 = { payload:"play" };
return [ [ msg0, msg1, msg2] ];
}
}

Arduino FM Radio

There are a few FM receiver modules that are available. We used an FM module that is based on the RDA5807M chip and unlike some of the other chips this one supports volume control. To keep our project compact we used the Arduino Nano, but we tested the UNO and Mega and they both worked well.

fmradio

There are a lot of options on how to control your FM radio. We liked the idea of using an old TV remote because this allowed us to change the volume and radio stations anywhere in the room. For this project we used:

• an I2C FM receiver module ($13)
• any Arduino module that has SDA and SCL pins
• an IR receiver ($5)
• a small bread board and some jumpers

The FM receiver module works on the I2C bus that connects to the SDA and SCL pins. Depending on which IR chip you use the wiring will vary slight. The key thing is to connect the data pin correctly. For our example we used pin 11.

circuit2

FM Module

When we first starting working this project there was no Arduino FM library available, so we started to by talking directly with the I2C bus. However now an Arduino FM library is available.

The RDA5807M chip [3] on the FM receiver module has a number of register addresses that we needed to write to. The key ones were:

  • REGISTER 2 – Initialize the chip (0xC003)
  • REGISTER 2 – Enable radio communications (0xC00D)
  • REGISTER 3 – Set the frequency
  • REGISTER 5 – Set the volume

We needed to pause between initializing and enabling radio communications. Setting the radio frequency is done by offsetting the frequency from the minimum range (870) and then splitting the value into high and low bytes.

The volume on register 5 is adjusted between a value of 0, the lowest, and 15 or 0xF the highest. There are other options on register 5 so our code changed the value from 0x84D0 to 0x84DF.

The Arduino modules uses the wire.h library to read and write to I2C devices. To write to a register the important commands are:

  • Wire.beginTransmission
  • Wire.write
  • Wire.endTransmission

An example using these commands would be:


//This is an example of setting the volume to 1
//This sets up communications to a device
Wire.beginTransmission(0x11); // 0x11 is the RDA5807M chip
Wire.write(0x05); // address 0x05 is where you want to write to
Wire.write(0x84); // write 0x84 to the first byte of address 0x05
Wire.write(0xD1); // write 0xD1 to the second byte of address 0x05
Wire.endTransmission(); // finish the write

We made a simple radio test program (Listing 1) that set up the radio to a local frequency at volume 1.


#include <Wire.h>

int freq;
int freqB;
byte freqH, freqL;

void setup()
{
Wire.begin();

// Initialize the RDA5807M chip

Wire.beginTransmission(0x11); // Device address is 0x11
Wire.write(0x02); // Register address 0x02
Wire.write(0xC0); Wire.write(0x03); // Initialize the settings
Wire.endTransmission(); // stop condition
delay(500); // wait 500ms

Wire.beginTransmission(0x11); // Device address is 0x11
Wire.write(0x02); // Register address 0x02
Wire.write(0xC0); Wire.write(0x0D); // Setup the radio for communications
Wire.endTransmission();
delay(500);

// Define an FM station to listen to

freq = 1079; // 107.9 MHz our local FM station
freqB = freq - 870; // chip needs to have freq offset from lowest freq (870)
freqH = freqB>>2; // you need to break the offset freq into 2 parts (hi/low)
freqL = (freqB&3)<<6; // Shift channel selection for matching register 0x03

Wire.beginTransmission(0x11);
Wire.write(0x03);
Wire.write(freqH); // write High freq byte
Wire.write(freqL + 0x10); // write Low freq byte
Wire.endTransmission();

// The volume is from 0-F and its the first bytes, leave all the bytes (0x84D0 - 0x84DF)

Wire.beginTransmission(0x11);
Wire.write(0x05);
Wire.write(0x84); Wire.write(0xD1); // set volume to 1
Wire.endTransmission();
}

void loop()
{

}

Finding TV Remote Codes

We used a small program to find the IR (Infrared) codes from our TV remote. For our program we used the volume up, volume down, channel up and channel down keys. Different TV remotes will have different codes so you will have to find the codes that work with your remote.


/*
IR TEST PROGRAM

PINOUTS:

LEFT = DATA PIN
MIDDLE = GND
RIGHT = 3.3 volts

*/
#include <IRremote.h>

int RECV_PIN = 11;

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup()
{
Serial.begin(9600);
irrecv.enableIRIn(); // Start the receiver
Serial.println("Setup Complete");
}

void loop()
{
if (irrecv.decode(&results))
{
Serial.println(results.value, HEX);
irrecv.resume(); // Receive the next value
delay(500);

}
}

ircode

When our IR test program was running we used the Arduino monitor window to show us the different key codes. We manually recorded these codes and used them in our final project.

Using a TV Remote

Our goal was to use a TV remote to change the FM station and to adjust the volume. There are a lot of websites you can use to find nearby radio stations. A good website for this is: http://radio-locator.com.

Our final program  used a number of predefined FM stations that would change with channel up and channel down on the TV remote. The remote’s volume up and down would change the radio’s volume. Remember to change the IR codes to match your TV remote, and the FM stations for your area.


// RDA5807M Radio controlled with a TV Remote
//
#include <Wire.h>
#include <IRremote.h>

int RECV_PIN = 11; //Connect the IR data pin in 11
IRrecv irrecv(RECV_PIN);
decode_results results;

int volume = 0; // start with the volume low
int channellist[]= {999,1029,1021,1079}; // Define some radio stations
int maxc = 4; // Define the number of radio stations used
int channel = 2; // Start with a favorite station

void setup()
{
Wire.begin();

Serial.begin(9600);

irrecv.enableIRIn(); // Start the receiver

radio_init();
setfreq(channellist[channel]);
setvolume(volume);

}
void loop() {
if (irrecv.decode(&results)) {

switch (results.value) {
case 0xE0E0E01F:
Serial.println("vol up");
if (volume < 15) {
volume++;
setvolume(volume);
}
break;
case 0xE0E0D02F:
Serial.println("vol down");
if (volume > 0) {
volume--;
setvolume(volume);
}
break;
case 0xE0E048B7:
Serial.println("chan up");
if (channel < maxc) {
channel++;
setfreq(channellist[channel]);
}
break;
case 0xE0E008F7:
Serial.println("chan down");
if (channel > 0) {
channel--;
setfreq(channellist[channel]);
}
break;
default:
Serial.println(results.value, HEX);
}
irrecv.resume(); // Receive the next value
}
delay(100);
}
//===============================
void setvolume(int thevolume)
{
byte volbyte;

volbyte = thevolume + 0xD0;
Wire.beginTransmission(0x11);
Wire.write(0x05);
Wire.write(0x84); Wire.write(volbyte);
Wire.endTransmission();
delay(500);
}
//===============================
void setfreq(int thefreq)
{
int freqB;
byte freqH, freqL;

freqB = thefreq - 870;
freqH = freqB >> 2;
freqL = (freqB & 3) <<6;

Wire.beginTransmission(0x11);
Wire.write(0x03);
Wire.write(freqH); // write frequency into bits 15:6, set tune bit
Wire.write(freqL + 0x10);
Wire.endTransmission();
delay(500);
}
//================================
void radio_init()
{
Wire.beginTransmission(0x11); // Device address 0x11 (random access)
Wire.write(0x02); // Register address 0x02
Wire.write(0xC0); Wire.write(0x03); // Initialize the settings
Wire.endTransmission();
delay(500); // wait 500ms to finalize setup

Wire.beginTransmission(0x11); // Device address 0x11 (random access)
Wire.write(0x02);
Wire.write(0xC0); Wire.write(0x0D); // Setup radio settings
Wire.endTransmission();
delay(500); // wait 500ms to finalize settings
}

Packaging our Project

We wanted to make our radio project portable, so we came up with two ideas. The first idea was to put all the electronics into a plastic container. For this we used a soap dish ($1) that we drilled three holes in. The first two holes were for the power and speaker cords. The last hole was for the IR receiver. To power our project we used a solar charger ($10), so we could listen to music outside.

soapdish1

Our second idea was to place the electronics inside the pocket of a cooler bag. It is important to have the IR receiver poking out of the pocket.

coolerbag

There are also some fun projects where you could use LCD Keyboard Shields or Touchscreens.

lcd