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:
| Raspberry Pi | SI470x |
|---|---|
| 3.3V (Pin 1) | 3.3V |
| GND (Pin 6) | GND |
| SDA (Pin 3) | SDIO |
| SCL (Pin 5) | SCLK |
| GPIO23 (Pin 16) | RST |
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:
|
1 2 |
i2c-bcm2708 i2c-dev |
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
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 |
/* i2c-init.c */ #include <wiringPi.h> int main() { int resetPin = 23; // GPIO23 int sdaPin = 0; // GPIO0 /* Setup GPIO access in BCM mode */ wiringPiSetupGpio(); /* Set pins as output */ pinMode(resetPin, OUTPUT); pinMode(sdaPin, OUTPUT); /* A low SDA indicates a 2-wire interface */ digitalWrite(sdaPin, LOW); /* Put chip into reset */ digitalWrite(resetPin, LOW); /* 1ms delay to allow pins to settle */ delay(1); /* Bring chip out of reset with SDIO set low and SEN pulled high (with pull-up resistor) */ digitalWrite(resetPin, HIGH); return 0; } |
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 resetYou can set a frequency and the volume (0-30) like this:
sudo ./rdspi tune 95.00
sudo ./rdspi volume 10All 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-initi2c-initsudo ln -s /home/pi/RdSpi/rdspi rdspi
Afterwards, you should be able to call the command from everywhere.
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As soon as I saw the title of this tutorial I wondered what using an RPi as a radio receiver has to do with using an RPi as a car PC. I’ve now read the entire tutorial…and I’m still wondering.
If you want to use the Pi as a Car PC (later tutorials) and want to have radio reception, this tutorial provides the basics.
I followed the tutorial but i am getting:
Unable to read Si4703!
Communication error
the i2cdetect -y 1 command finds ok the module
Any solutions to the communication error?
Can the audio be accessed via the internet?? If so how?
Same! Not working! the i2cdetect -y 1 command finds module, but ommunication error with rdspi.
If youre using a newer wiringpi version, specifically rev2, in your i2c-init.c script, on line 6, change the SDA pin from 0 to 2. Just spend a few hours digging to figure this out.
Depending on the wiringpi version being used (recent attempts will be Rev 2), the SDA pin in the i2c-init.c script (line 6) should be defined as 2, not 0. Referenced at http://wiringpi.com/pins/.