RaspberryPi Radio Player Interface

A simple API handling server for PiFM to control Raspberry Pi fm transmission. Can be easily extended to serve web pages or to be controlled using buttons connected to GPIO pins for standalone function.

Since Python has an easily modifiable server, this was easy and helpful.

Tested with RaspberryPi v1 model B and Zero. For others just update the pifm binary with a working one and change command line for pifm in player.py

player = subprocess.Popen(["./pifm_binary_name", parameters...], stdin=player.stdout)

To test pifm try:

avconv -i MUSIC_FILE s16le -ar 22.05k -ac 1 - | sudo ./pifm - FREQ

Changes in latest version (13 July 2016):

• Support for subscription to player status updates
• Working Android controller application (RiPlay for Android)
• Switch between radio and audio playback (restarts song)

Features todo:

• Volume control
  • ALSA volume control (should be simple)
  • Multithreaded pifm to change volume on the fly

Install instruction (on RPi a.k.a. Server):

# Install avconv 
sudo apt-get update
sudo apt-get install libav-tools

# Get Server code
git clone https://github.com/hex007/pifm_server
cd pifm_server
g++ -O3 -o pifm pifm.c
mkdir Music
# copy music files to Music/

# Start server
sudo python main.py

Optional: Start server at startup

# To start server at startup:
sudo nano /etc/rc.local

# In nano INSERT BEFORE return 0
cd /home/pi
sudo python main.py > latest.log &

API Documentation

Using a client to send requests to Server

1. Get Music Collection : returns JSONobject

    curl http://raspberrypi.local:8080/api/collection
   
    # For formatted Collection ->
    curl http://raspberrypi.local:8080/api/collection | sed "s|\", \"|\"\\n\"|g"
   

2. Get playlist : returns JSONarray

    curl http://raspberrypi.local:8080/api/playlist
   

3. Get Broadcast Frequency

    curl http://raspberrypi.local:8080/api/freq
   

4. Play X = [N|all|shuffled] from Collection

    curl http://raspberrypi.local:8080/api/play/X
   

5. Queue X = [N|all|shuffled] from Collection

    curl http://raspberrypi.local:8080/api/queue/X
   

6. Stop player, leave queue as playlist

    curl http://raspberrypi.local:8080/api/stop
   

7. Start player, continue with playlist

    curl http://raspberrypi.local:8080/api/start
   

8. Skip song in playlist

    curl http://raspberrypi.local:8080/api/skip
   

9. Clear playlist; keeps current song if playing

    curl http://raspberrypi.local:8080/api/clear
   

Subscription management

Changes in the player state can be subscribed to using:

 curl http://raspberrypi.local:8080/api/subscribe?port=$PORT

Once a user is subscribed to the player, every state change is reported to the subscriber at the port requested $PORT. The IP address is the same as the one requesting the subscription .The client machine must have a server running to accept status updates. If the status update request from the RPi to client fails then the client is automatically unsubscribed from the stats updates.

To manually request for unsubscription send request:

curl http://raspberrypi.local:8080/api/unsubscribe

Switch outputs

Audio output (defaults to radio) can be changed using the following requests:

# To set output as Audio (3.5mm Jack or HDMI)
curl http://raspberrypi.local:8080/api/output/audio

# To set output as Radio (PiFM)
curl http://raspberrypi.local:8080/api/output/radio

Multiple attempts at switching causes RPi to output noise and a reboot is needed to resolve the issue.