Hey guys! Ever found yourself needing to tweak those serial port settings in Ubuntu? Whether you're connecting to a microcontroller, debugging some embedded systems, or just playing around with hardware, getting the serial port parameters right is super important. In this guide, we'll walk through everything you need to know to configure your serial port like a pro. Let's dive in!

Understanding Serial Port Parameters

Before we get our hands dirty, let's quickly go over what serial port parameters actually are. These settings define how data is transmitted and received through the serial port. Getting them wrong can lead to garbled data or no communication at all, so pay close attention! The key parameters include:

• Baud Rate: This is the speed at which data is transmitted, measured in bits per second (bps). Common values include 9600, 115200, and so on. Both devices communicating over the serial port must use the same baud rate.
• Data Bits: This specifies the number of bits used to represent each character of data. Typically, this is 7 or 8 bits. The standard is often 8 bits.
• Parity: Parity is a method of error checking. It can be set to even, odd, or none. If parity is enabled, an extra bit is added to each character to ensure that the total number of 1s is either even or odd, depending on the parity setting.
• Stop Bits: These bits indicate the end of a data transmission. Usually, this is 1 or 2 bits. One stop bit is the most common.
• Flow Control: Flow control manages the flow of data between devices to prevent data loss. Hardware flow control (RTS/CTS) and software flow control (XON/XOFF) are the common types. Often, no flow control is also used.

These parameters ensure that both devices communicating over the serial port are speaking the same language, preventing data corruption and ensuring smooth communication. Now that we know what we're dealing with, let's jump into setting these parameters in Ubuntu.

Method 1: Using the stty Command

The stty command is a powerful tool for configuring serial port settings directly from the command line. It's super flexible and lets you set all the parameters we talked about earlier. Here’s how to use it:

Identifying Your Serial Port

First, you need to know the name of your serial port. In Ubuntu, serial ports are usually named something like /dev/ttyS0 (for physical serial ports) or /dev/ttyUSB0 (for USB serial adapters). To figure out which one you're using, you can try listing the contents of the /dev directory and looking for devices that start with tty. A handy trick is to use dmesg after plugging in your USB serial device; it usually tells you which /dev/tty* device was created.

ls /dev | grep tty

Or, use dmesg:

dmesg | grep tty

Setting Basic Parameters

Once you know your serial port, you can use stty to set the baud rate, data bits, parity, and stop bits. Here’s an example:

stty -F /dev/ttyUSB0 115200 cs8 -parenb -cstopb

Let's break this down:

• -F /dev/ttyUSB0: This specifies the serial port you want to configure.
• 115200: This sets the baud rate to 115200 bps.
• cs8: This sets the data bits to 8.
• -parenb: This disables parity.
• -cstopb: This sets one stop bit. If you want two stop bits, use cstopb.

Setting Flow Control

To set flow control, you can use the crtscts option for hardware flow control (RTS/CTS) or ixon and ixoff for software flow control (XON/XOFF). To disable flow control, use -crtscts, -ixon, and -ixoff.

Here’s an example with hardware flow control:

stty -F /dev/ttyUSB0 crtscts

And to disable it:

stty -F /dev/ttyUSB0 -crtscts

Saving Your Settings

One important thing to note is that the settings you apply with stty are usually only valid for the current session. Once you close the terminal or reboot your system, these settings will be lost. To make the settings permanent, you need to add the stty command to your .bashrc or .profile file. Open the file with your favorite text editor:

nano ~/.bashrc

Add the stty command to the end of the file, save it, and then source the file to apply the changes:

source ~/.bashrc

Now, your serial port settings will be applied automatically every time you open a new terminal!

Method 2: Using setserial

Another useful tool is setserial, which is specifically designed for configuring serial ports. It's particularly handy for setting low-level hardware settings. Note that setserial often requires root privileges.

Installing setserial

If setserial isn't already installed on your system, you can install it using apt:

sudo apt update
sudo apt install setserial

Configuring the Serial Port

To use setserial, you need to know the device name. Let's assume it's /dev/ttyS0. You can then use setserial to configure various parameters. For example, to set the baud rate and other settings, you can use the following command:

sudo setserial -a /dev/ttyS0 spd_vhi

Here, spd_vhi is a special baud rate that allows you to set a custom baud rate. You can then set the divisor to achieve the desired baud rate. For example, to set the baud rate to 57600, you can use:

sudo setserial -a /dev/ttyS0 divisor 3

This command sets the divisor to 3, which, combined with spd_vhi, achieves a baud rate of 57600. Note that the exact divisor value depends on the hardware and the desired baud rate.

Checking the Configuration

To verify the current configuration of the serial port, you can use the following command:

sudo setserial -g /dev/ttyS0

This will display the current settings of the serial port, including the baud rate, UART type, and other parameters. Using setserial is particularly useful for setting hardware-specific parameters that stty might not cover.

Method 3: Using a Graphical Interface (GUI)

If you prefer a graphical interface, you can use tools like gtkterm or minicom to configure your serial port. These tools provide a user-friendly way to set the serial port parameters without having to use the command line.

Installing gtkterm

If you don't have gtkterm installed, you can install it using apt:

sudo apt update
sudo apt install gtkterm

Configuring the Serial Port in gtkterm

Once installed, you can launch gtkterm from the terminal:

gtkterm

In gtkterm, go to Configuration > Port. Here, you can set the serial port, baud rate, data bits, parity, and stop bits. Once you've set the parameters, click OK to save the settings.

Using minicom

minicom is another popular terminal program that allows you to configure serial ports. To install it:

sudo apt update
sudo apt install minicom

Configuring the Serial Port in minicom

To configure minicom, launch it with:

sudo minicom -s

This will open the setup menu. Go to Serial port setup and configure the device, baud rate, parity, and other settings. Once you're done, save the configuration and exit. minicom stores its configuration in a file, so the settings will persist across sessions.

Troubleshooting Common Issues

Even with the right settings, things can sometimes go wrong. Here are some common issues and how to troubleshoot them:

• No Data Received:

  • Check the Baud Rate: Ensure that the baud rate on your Ubuntu machine matches the baud rate of the device you're connecting to.
  • Verify the Serial Port: Make sure you're using the correct serial port (e.g., /dev/ttyUSB0).
  • Check the Wiring: Ensure that the serial cable is properly connected and that the wiring is correct. Sometimes, TX and RX lines need to be crossed.

• Garbled Data:

  • Check Parity, Data Bits, and Stop Bits: Ensure that these settings match the settings of the device you're connecting to. Mismatched settings can lead to garbled data.
  • Flow Control Issues: Try disabling flow control to see if that resolves the issue. If it does, then the problem might be with the flow control settings.

• Permission Issues:

  • User Permissions: Ensure that your user has the necessary permissions to access the serial port. You might need to add your user to the dialout group:

  sudo usermod -a -G dialout $USER
  newgrp dialout
  

Conclusion

And there you have it, guys! Configuring serial port parameters in Ubuntu might seem daunting at first, but with the right tools and knowledge, it becomes a breeze. Whether you prefer the command line or a graphical interface, Ubuntu provides multiple ways to get the job done. Remember to double-check your settings, troubleshoot common issues, and save your configurations for future use. Happy serial communicating!