In our Raspberry Pi serial connection tutorial, we will be covering all you need to know about UART on the Raspberry Pi. This includes everything from wiring and configuration, to programming and usage. We will also provide some useful tips to help you get started with serial communication on your Raspberry Pi. So whether you’re a beginner or an experienced user, there’s something for everyone in this tutorial!
What are Raspberry Pi Serial Pins?
The Raspberry Pi has two pins that can be used for serial communication. These are known as the Tx (transmit) and Rx (receive) pins, and they are located on the GPIO header. When connected, the TX pin’s role is to send data from the Raspberry Pi to a different device, while the RX pin is used to receive data.
UARTs are frequently utilized to link PCs and microcontrollers. They’re also what the Raspberry Pi Serial uses for communication, so it’s vital that you understand how they work! [1], [2]
How does UART communication work?
UART utilizes asynchronous serial communication. This means that the data is not sent in a continuous stream. Instead, it is sent in packets. This has the advantage that UART can be used with devices that have different clock speeds.
A packet is a group of bytes that are sent together. The first byte in a packet is called the header. The header includes information about the rest of the packet, such as how long the data is and which device it’s for.
UART is commonly used to connect devices like modems, GPS modules, and sensors. It is also used to connect the Raspberry Pi to other devices like computers and microcontrollers.
Its other use is debugging. For example, you can use UART to view data that is being sent from the Raspberry Pi to a different linked device. This can be useful for troubleshooting issues with your code or hardware.
After the header comes the data itself. This can be any number of bytes, including zero bytes. The last byte in a packet is called the trailer. It contains information about the rest of the packet, like how many bytes of data there are.
When using UART, be sure that the baud rates of both devices match. The baud rate is a measure of how much data bits can be sent per second. If the baud rates are different, the devices will not be able to transfer data with each other. [1], [2], [3], [4]
Serial communication between Raspberry Pi and PC
The possibilities you can achieve by using Raspberry Pi are as endless and wide-ranging as your imagination. You can use it to communicate with another computer, microcontroller, or even another Raspberry Pi. In this tutorial, we will be using it to communicate with a computer.
To do this, you will need:
- Raspberry Pi 3
- A computer with a serial port
- Arduino UNO R3
- A TTL to USB converter
- A male-to-male USB cable
Use a USB converter to connect the serial to the Raspberry Pi
Next, connect the converter to your PC and open the Device Manager. Under Ports (COM & LPT), you should see a new port called USB Serial Converter. If you don’t see it, try restarting your computer. [1], [2], [5]
Configure the Raspberry Pi in the Device Manager
Then, right click on it and set up the configuration. Double check that the set baud rate is set to 115200, and that the flow control is set to None. Click on OK and you should be able to communicate with your Raspberry Pi. [1], [2], [5]
Enable UART in the Raspberry Pi
To enable UART in the Raspberry Pi, we need to edit the config.txt file. This can be done with a text editor such as nano or Vim by entering the following command:
sudo nano /boot/config.txt
One you’re opened the config file, add these lines to the bottom of the file:
Enable UART
enable_uart=1
Save and close the file. Then, reboot the Raspberry Pi.
After that enter the code:
sudo systemctl disable serial-getty@ttyS0.service
Open cmdline.txt and add this text:
console=serial0,115200
save and close the file.
Now, you can turn off and reboot the Raspberry and install the minicom terminal to communicate with the board.
sudo apt-get install minicom
Once the installation is complete, open the terminal and enter the next command as written:
minicom -b 115200 -o -D /dev/ttyUSB0
This will open the Minicom terminal at the baud rate of 115200 and you should be able to communicate with your Raspberry Pi. If everything is working correctly, you should see a prompt that says “Raspberry Pi” and you will be able to type commands into the terminal and see the output on your computer. [1], [2], [5]
How to Connect Raspberry Pi to Arduino
There are many ways to connect both boards, and the simplest and fastest one is to get an USB cable to link both devices.
But before that, you will need to connect Arduino to your PC, luckily you won’t need to configure anything, just plug it in and you’re ready to go. For Raspberry Pi however, some configuration will be required.
Connect it by using shh and open the terminal, now you will need to make your Raspberry Pi detect an Arduino board.
To do this, type this command:
ls /dev/ttyACM*
If you see a device that starts with “/dev/ttyACM“, that’s your Arduino.
We’ll now enable UART communication on the Raspberry Pi board by updating its configuration file. We’ve already gone over how to do this, so let’s get started. [1], [2]
Adding hardware permissions
We must give both boards permission to communicate via the UART in order for them to collaborate. This can be accomplished using the chmod command.
sudo adduser username dialout
It will allow any device to connect to your Raspberry Pi board.
It now should be possible to link both your Arduino and Raspberry Pi together and send data back and forth! Another important thing to know however, is how to use Python language capabilities to control an Arduino board. We will explain it right now.
Installing Python library
Python is arguably one of the most flexible programming languages in existence. With it, you can create an endless variety of applications to meet your needs and desires. In this case, we are using it to communicate with an Arduino board. Python has several libraries that allow us to easily interface with Arduino boards, which makes it the perfect choice for this project.
sudo apt-get install python-3.pip
Once pip is installed, we can install the serial library by entering the following command:
python3 -m pip install pyserial
After the installation is complete, we can start writing our own Python programs to read the data from the serial port. [1], [2]
Simple Communication Example
In this example, we’ll send the data that was received by the Arduino board to the console. We’ll also send a simple message to the Arduino.
First, connect Ardunino to your PC, open Arduino IDE on your PC and type the following code:
void setup() {
Serial.begin(9600);
}
void loop() {
Serial.println(“Arduino says hello!”);
delay(1000);
}
Explanation of the code
The code is pretty simple. We just employ the Serial.print procedure to start up serial communication and send an info message to the Arduino board. We used 9600 as the baud rate because this is the most popular option. However, you may change it to whatever you like. We are also using a delay of 1000 milliseconds to see the message on the console.
The Python code for Raspberry Pi should look like the one below:
import time
import serial
if __name__ == ‘__main__’:
ser = serial.Serial(‘/dev/ttyACM0’, 9600, timeout=1)
ser.reset_input_buffer()
while True:
if ser.in_waiting > 0:
line = ser.readline().decode(‘utf-8’).rstrip()
print(line)
How Does this code work?
The first two lines are imports. The time import is so we can use the sleep function to control how often our loop runs. The serial import gives us access to all of the functions in the pySerial library we downloaded earlier.
Next, we have an if statement that checks whether this file is being run as a script or imported as a module. This is good practice and helps to prevent your code from doing things it shouldn’t when someone tries to import it.
After that, we instantiate the Serial class with the name ser. This establishes a connection over USB at a baud rate of 9600 bps. Keep in mind that you have to use the same baud rate as the one you set in Arduino code. We also set a timeout of one second. This way, if there is nothing being sent from the Arduino, our program won’t get stuck waiting forever.
We first check whether there is anything in the serial buffer with ser.in_waiting in our while loop’s inner scope. We read it line by line and decode it from bytes to a string if there is something in the serial buffer. We also strip off any whitespace characters like spaces or newlines. Finally, we print out the resulting string.
The main function of this code is to read the data incoming from the Arduino board and print it to the console. We are using the exact baud rate as in our Arduino code so that they can communicate properly.
This code will print the data that is received from the Arduino board to the console. You should see the greeting message you typed printed on the screen with one second intervals. Congratulations, you’ve just successfully communicated with both boards!
Now that you can read data from Arduino, you may do all sorts of creative things with it, such as turning on an LED connected to a Raspberry Pi. Let your imagination fly! [1], [2]
The Common Errors You Should Keep in Mind
When using the serial interface, there are a few common errors to be aware of.
If you get an error starting with serial.serialutil.SerialException: [Errno 13], this means you don’t have permission to access the serial port.
You can fix this by opening the terminal and typing in “sudo adduser your_username dialout”.
If you get an error such as AttributeError: ‘module’ object has no attribute ‘Serial’, make sure that you are running Python version 3 or higher. The serial module is not available in lower versions of Python.
Another error you may encounter is a /usr/bin/python3: No module named pip. This means that you do not have pip installed. [1], [2]
Check more posts to improve your knowledge in electronics:
Raspberry Pi Serial (UART) Communication Indicators
| Indicator | Description |
|---|---|
| Baud Rate | The data transmission rate in bits per second. |
| Data Bits | The number of data bits in each UART frame. |
| Stop Bits | The number of stop bits used for error detection. |
| Parity | Error-checking method for data integrity. |
| Flow Control | Control mechanism for data flow between devices. |
The table above showcases key indicators related to UART communication on the Raspberry Pi:
- Baud Rate: Represents the data transmission rate in bits per second (bps). It determines how fast data is sent between devices.
- Data Bits: Indicates the number of data bits in each UART frame. Common values are 8, 7, or 9 bits, determining the amount of data sent in a single communication packet.
- Stop Bits: Defines the number of stop bits used to indicate the end of a data frame. Stop bits provide a brief pause between data packets, allowing the receiving device to process the information.
- Parity: Refers to an error-checking method used to ensure data integrity during transmission. Parity can be “None” (no error checking), “Even” (even-parity), or “Odd” (odd-parity).
- Flow Control: Involves control mechanisms to manage data flow between devices, preventing data loss or buffer overflow. Common flow control options include “None” (no flow control), “XON/XOFF” (software-based flow control), and “RTS/CTS” (hardware-based flow control).
Configuring UART communication with the appropriate values for these indicators is crucial to establishing reliable and efficient serial communication between Raspberry Pi and other connected devices.
FAQ
How do I use UART on my Raspberry Pi?
To use Raspberry Pi serial connection with your computer, you need a USB to TTL Serial Cable Converter. This cable will convert the USB signals to RS-232 levels that your computer expects.
Once you’ve connected your computer and Raspberry Pi, you’ll need to open a terminal window on your computer and type the following command:
sudo screen /dev/ttyAMA0 115200
This will start a session with UART at 115200 baud rate. You can now type commands into the terminal window on your computer and see the results on the Raspberry Pi. To save the file, press CTRL + X, Y and Enter.
How do I read serial data on Raspberry Pi?
To read serial data on the Raspberry Pi, you will need to install a terminal program. One popular option is called Minicom. After installing Minicom, you can run it by typing minicom into a terminal window. Once Minicom is running, you can access the serial port by selecting Device > Serial Port and choosing the correct device from the list.
If you are not sure which device is your serial port, you can open up a terminal window and type dmesg | grep tty to print out a list of all devices that were detected by the kernel. The serial port will be one of those devices.
Does the Raspberry Pi 3 model B board have a UART pin?
Yes, Raspberry Pi has UART pins. The header pins are located on the board near the micro USB port. They are marked as TXD and RXD.
What are the basic connections required for UART communication on Raspberry Pi?
To enable UART communication on Raspberry Pi, you’ll need to connect the TX (transmit) and RX (receive) pins of the Raspberry Pi to the corresponding TX and RX pins of the UART device you want to communicate with. Additionally, ensure both devices share a common ground connection.
Can I use GPIO pins for UART communication on Raspberry Pi?
Yes, Raspberry Pi’s GPIO pins can be used for UART communication. GPIO14 (TXD0) is used for transmitting data, and GPIO15 (RXD0) is used for receiving data. Remember to configure the UART settings properly in software.
How do I enable UART on Raspberry Pi through the command line?
To enable UART on Raspberry Pi, use the `raspi-config` utility. Open the terminal and type `sudo raspi-config`. Navigate to “Interfacing Options,” then “Serial.” Choose “No” for the login shell and “Yes” for the serial port hardware. Reboot the Raspberry Pi for the changes to take effect.
Which programming languages can I use for UART communication on Raspberry Pi?
You can use various programming languages like Python, C, C++, and even languages like Node.js to communicate with UART devices on Raspberry Pi. Libraries and modules are available for each language to simplify UART communication.
What is the default baud rate for UART on Raspberry Pi?
The default baud rate for UART on Raspberry Pi is 115200. However, you can change the baud rate to match the one used by the device you’re communicating with, depending on your specific application requirements.
Can I use UART for communication between two Raspberry Pi boards?
Yes, you can establish UART communication between two Raspberry Pi boards by connecting the TX pin of one board to the RX pin of the other and vice versa. Remember to ensure that both boards are using the same baud rate and have a common ground connection.
How do I troubleshoot UART communication issues on Raspberry Pi?
If you encounter UART communication problems, you can check for loose connections, ensure the correct baud rate settings, and verify that both devices are using the same voltage levels. Additionally, inspecting the error logs and using appropriate debugging techniques will help diagnose and resolve any issues.
Useful Video: [ENG] Raspberry Pi! Ep:5 – UART Usage – C (termios)
Conclusion
So, what have we learned? Serial communication is a way to transfer data between devices. UART is one of the most popular serial protocols for that job. In this article, we’ve shown you how to connect a Raspberry Pi to a PC and Arduino using UART serial communication. Now it’s your turn to try it out! Once you have everything set up, send some data back and forth between the devices to see how they work together. If you run into any problems, be sure to check out our troubleshooting guide for help. We hope you create something really cool with your Raspberry Pi!
References:
- https://pimylifeup.com/raspberry-pi-serial/
- https://roboticsbackend.com/raspberry-pi-arduino-serial-communication/#What_is_Serial_communication_with_UART
- https://www.analog.com/en/analog-dialogue/articles/uart-a-hardware-communication-protocol.html
- https://pinout.xyz/pinout/uart#
- https://electropeak.com/learn/raspberry-pi-serial-communication-uart-w-arduino-pc/