Use Raspberry Pi as a Radio Receiver (FM Car Radio, Car PC)

Anyone who has ever thought of a car PC has certainly dealt with radio reception. Now there are not too many possibilities to use the Pi as an FM receiver, but one is the Si4703 module, which is used here.

In a previous tutorial, I have already shown how to use the Raspberry Pi as a
radio transmitter. This part is about how to receive and play radio frequencies.

Required Hardware Parts

To use your Raspberry Pi as a radio receiver, you will need the following:

• Si470x Receiver Module
• Aux Cable / Headphones
• Female-Female Jumper Cable

Setup

The connection of the Si470x module is as follows:

On the schematic picture, I have connected GND to Raspberry Pi pin 25, which is also a ground connection.

Preparation

(In order to compile the software, wiringPi must be installed, if you have not already done so, you can read how to do it here)

First, we activate SPI and I2C. If you already did that in a previous tutorial, you can skip this step.

sudo raspi-config

Under “Interfacing Options” there is the entry “I2C”, which we should activate. For older Raspbian versions, the entries in the file /etc/modprobe.d/raspi-blacklist.conf must be commented out (with a #).

Then we edit the modules file:

sudo nano /etc/modules

At the end of the file we add the following two lines:

Lastly, we install the necessary tools if they are not already available.

sudo apt-get update
sudo apt-get install i2c-tools

Software

git clone https://github.com/achilikin/RdSpi && cd RdSpi

Then we compile:

make

Before we start, however, the module must first be activated via I2C. For this we create another script in this folder:

sudo nano i2c-init.c

After saving (CTRL + O, CTRL + X) we compile it.

gcc -o i2c-init i2c-init.c -lwiringPi

This script initializes the module so that it can be used (it must be re-initialized after each reboot, so it would make sense to set the program to Autostart).

sudo ./i2c-init

To test if it has been detected, you can type i2cdetect -y 1, which should produce such an output:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: 10 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Test the Raspberry Pi FM Receiver

Once the module has been initialized, we can use the aux cable to connect our speakers/headphones (which serve as antennas) and search for stations.

First we have to reset the receiver:

sudo ./rdspi reset

You can set a frequency and the volume (0-30) like this:

sudo ./rdspi tune 95.00
sudo ./rdspi volume 10

All other commands can be viewed on the Github project page.

PS: If you want to call the compiled files directly without ./ , you can distribute the following rights

chmod +x i2c-init
chmod +x rdspi

Then just add the path variable and create a link (you can get the path of the current directory with pwd):

export PATH=$PATH:/home/pi/RdiSpi
cd /usr/bin
sudo ln -s /home/pi/RdSpi/i2c-init i2c-init
sudo ln -s /home/pi/RdSpi/rdspi rdspi

Afterwards, you should be able to call the command from everywhere.