UP-FM Transmitter

DESCRIPTION

A Raspberry Pi-based program FM transmitter that plays online UP-FM music radio. Radio receivers can tune in to 87.5MHz if the transmitter is in range.

Individuals from the different UP campuses, UP alumni and friends in different locations, lovers of Filipino indie music are encouraged to build and use this device to broadcast UP-FM in their areas.

COMPONENTS

A. For PIFM:

• Raspberry PI (model B).

• SD Card with Raspbian "Wheezy" OS (operating system) installed.

• USB Micro Cable

• Ethernet Cable

• Power Brick (5 volts, 2 amperes)

• Solid wire,no.22 and GPIO Cable (for the antenna)

• Soldering iron, Soldering lead, Electrical tape

B. For Programming:

• PC Monitor

• USB Mouse

• USB Keyboard

• VGA to HDMI Cable

PROCEDURES

A. Making a Simple Antenna

Since you may not have an ideal antenna, you will use a solid wire (no.22) as substitute. Cut a solid wire about 32 centimeters and stripe one end at least 1 cm. Also cut the GPIO cable wire near the socket and leave at least 1 cm wire on it. Stripe the wire near the GPIO socket. Combine both ends of the solid wire and GPIO socket using lead and soldering iron. Wrap the soldered wire and GPIO with the tape (see pictures below).

B. Installing and Running Raspbian "wheezy

You will now prepare the PIfm in Raspberry PI. To do so, you must have an SD card, with Raspbian "wheezy" OS installed. One way to do it is to download and install the Win 32 disk imager to your windows PC. Also download zip file of Raspbian "wheezy" and extract the file. Plug in your SD card. Write the disk image file on the SD card.Then you have now the installed Raspbian "wheezy" OS in your SD card.

Enabling network connection

C. Programming the PIFM

Once you have installed the Raspbian "wheezy" and ran it to your Raspberry PI, you can now program the UP-FM transmitter from LXterminal.

• open your lxterminal.

• create a dedicated directory within the home directory and download the pifm files from icrobotics site as follows:

        cd ~

        mkdir pifm

        cd pifm 

        wget http://www.icrobotics.co.uk/wiki/images/c/c3/Pifm.tar.gz

        tar -xvf Pifm.tar.gz

• download the application called sox (Sound Exchange) package. This is required to stream the internet radio and pipe it to PIFM program for transmission.

        sudo apt-get install sox libsox-fmt-all

• create a script to make it easier to execute.

        sudo nano pifmradio.sh

Type following command line inside the script and press ctrl+x, Y and then Enter to save.

#!/bin/bash
sox -v .9 -t mp3 "http://updox.upd.edu.ph/stream/2/;stream.nsv" -t wav --input-buffer 80000 -r 22050 -c 1 - | sudo /home/pi/pifm/pifm - 87.5

• Change the mode of the script to be executable.

        sudo chmod +x pifmradio.sh

• To run the script in the background, execute the ff command:

        ./pifmradio.sh &
       

You may get the following warning message:

          wav: Length in output .wav header will be wrong since can't seek to fix it

You may safely ignored it. This is due to the fact that you are using a piped output to pifm and sox is issuing a warning that it is not possible to go back to the beginning of the stream and write the correct size into the RIFF/WAVE header, like it would be possible with a physical file.

Autostarting UP-FM at boot

• Create a folder to store the script in

          mkdir ./bin

          cd ./bin

• Create the script using the nano text editor

          sudo nano script_auto_run

• In the nano editor, type this script:

          #!/bin/bash

          # Script to start our application

          echo "Doing autorun script..."

          sudo /home/pi/pifm/pifmradio.sh &

Note that when executing a command without logging in, you have to provide full paths to everything.

Save it by pressing Ctrl+X, " Y", ENTER

• This script needs to be made executable by typing this :

          sudo chmod 755 script_auto_run

• You can test the script works by typing

          /home/pi/bin/script_auto_run

• Setting it to be run

To launch the script at startup, edit the “rc.local” file:

          sudo nano /etc/rc.local

• Add the following line:

          /home/pi/bin/script_auto_run

Save it by pressing Ctrl+X, " Y", ENTER

Reboot your RPi and it will run.

Development Team

• Jhon Mark Sorio
• Nestor Tiglao (consultant)
• Peter Sy (project management)

UP-FM transmitter in action

see sample clip

Cost Estimate

• Raspberry Pi Type B 512MB: Php 1,500
• SD Card
• wire antenna

See Also

• UP-FM