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Ruby Serial Port Communication: Tips and Tricks for Reading Data


How to Read Data from Serial Port in Ruby: A Complete Guide




If you want to communicate with a device that uses a serial port, such as an Arduino board, you can use Ruby to read and write data from it. In this article, you will learn how to use the serialport gem to create a serial port object, configure its parameters, and read data from it.




ruby read data from serial port



What is a Serial Port?




A serial port is a physical interface that allows data to be transferred between a computer and a peripheral device, such as a modem, printer, scanner, or microcontroller. A serial port sends and receives data one bit at a time, using a single wire for each direction. The data is encoded using a specific protocol, such as RS-232 or USB.


How to Install the SerialPort Gem




The serialport gem is a Ruby library that provides an easy way to access and control serial ports. You can install it using the following command:


gem install serialport


Alternatively, you can add it to your Gemfile and run bundle install.


How to Create a Serial Port Object




To use the serialport gem, you need to create a SerialPort object that represents the serial port you want to communicate with. You can do this by passing the port identifier and optionally some configuration parameters to the SerialPort.new method. For example:


require 'serialport'


ser = SerialPort.new("/dev/ttyACM0", 9600)


This creates a SerialPort object for the port "/dev/ttyACM0" with a baud rate of 9600 bits per second. The port identifier may vary depending on your operating system and device. On Windows, it may be something like "COM1". On Linux, it may be something like "/dev/ttyS0". On Mac OS X, it may be something like "/dev/cu.usbmodem1411". You can use the dmesg command or the Device Manager to find out the correct port identifier for your device.


The configuration parameters are optional and have default values. You can specify them as positional arguments or as a hash. The parameters are:


  • Baud rate: The speed of data transmission in bits per second. The default is 9600.



  • Data bits: The number of bits used to represent each character of data. The default is 8.



  • Stop bits: The number of bits used to indicate the end of a character. The default is 1.



  • Parity: The method of error detection for each character. The default is SerialPort::NONE.



  • Flow control: The method of controlling the flow of data between the sender and the receiver. The default is SerialPort::NONE.



You can use constants defined in the SerialPort class to specify these parameters. For example:


require 'serialport'


ser = SerialPort.new("/dev/ttyACM0", 19200, 7, 2, SerialPort::EVEN)


This creates a SerialPort object with a baud rate of 19200 bits per second, 7 data bits, 2 stop bits, and even parity.


How to Read Data from a Serial Port




To read data from a serial port, you can use any of the Ruby IO methods, such as read, getc, readline, readlines, etc. For example:


require 'serialport'


ser = SerialPort.new("/dev/ttyACM0", 9600)


data = ser.read(10) # read 10 bytes


puts data # print the data


How to Write Data to a Serial Port




To write data to a serial port, you can use any of the Ruby IO methods, such as write, putc, print, puts, etc. For example:


require 'serialport'


ser = SerialPort.new("/dev/ttyACM0", 9600)


ser.write("Hello, world!") # write a string


ser.putc(65) # write a byte


This writes the string "Hello, world!" and the byte 65 (which corresponds to the ASCII character 'A') to the serial port. The data will be sent to the device connected to the port, such as an Arduino board.


How to Close a Serial Port




When you are done with using a serial port, you should close it to free up the resource and avoid errors. You can do this by calling the close method on the SerialPort object. For example:


require 'serialport'


ser = SerialPort.new("/dev/ttyACM0", 9600)


# do some reading and writing


ser.close # close the port


You can also use the SerialPort.open method with a block, which will automatically close the port when the block ends. For example:


require 'serialport'


SerialPort.open("/dev/ttyACM0", 9600) do ser


# do some reading and writing


end # port is closed here


How to Handle Errors and Exceptions




When working with serial ports, you may encounter some errors and exceptions that can disrupt your communication. For example, you may get an Errno::EIO exception if the device is disconnected or turned off, or an ArgumentError if you pass invalid or unsupported values to the SerialPort methods. You can use the Ruby rescue keyword to handle these errors and exceptions gracefully. For example:


require 'serialport'


begin


ser = SerialPort.new("/dev/ttyACM0", 9600)


# do some reading and writing


rescue Errno::EIO


puts "Device is not connected!"


rescue ArgumentError => e


puts "Invalid argument: #e.message"


ensure


ser.close if ser # close the port if it is open


end


This code tries to create a SerialPort object and do some reading and writing. If it encounters an Errno::EIO exception, it prints a message and exits. If it encounters an ArgumentError, it prints the error message and exits. In any case, it closes the port if it is open.


How to Test Your Serial Port Communication




To test your serial port communication, you can use a simple device such as an Arduino board that can send and receive data over a serial port. You can write a sketch that reads data from the serial port and echoes it back, or sends some data periodically. For example:


// Arduino sketch that echoes data from serial port


void setup()


Serial.begin(9600); // set baud rate


void loop()


if (Serial.available() > 0) // check if there is data available


char c = Serial.read(); // read a byte


Serial.write(c); // write the same byte back



This sketch reads a byte from the serial port and writes it back. You can use this sketch to test your Ruby code that writes and reads data from the serial port.


How to Choose a Ruby Serial Port Library




There are several Ruby libraries that can help you communicate with serial ports, but they may have different features, compatibility, and performance. Here are some of the most popular ones and their pros and cons:


  • serialport: This is the oldest and most widely used Ruby serial port library. It supports POSIX (Linux, *BSD, Solaris, AIX, Mac OS X), Cygwin and native Windows. It also provides low-level functions to check and set the state of the signals on the line. However, it requires native compilation and may not work well with newer Ruby versions or implementations .



  • rubyserial: This is a newer and simpler Ruby serial port library that uses RubyFFI to access the system libraries. It supports all of the most popular Ruby implementations (MRI, JRuby, & Rubinius) on the most popular operating systems (OSX, Linux, & Windows). It does not require any native compilation or installation of external dependencies. However, it does not provide low-level functions to check and set the state of the signals on the line.



  • serialport-pure: This is a pure Ruby serial port library that does not rely on any external libraries or native extensions. It supports POSIX (Linux, *BSD, Solaris, AIX, Mac OS X) and native Windows. It also provides low-level functions to check and set the state of the signals on the line. However, it may be slower than other libraries and may not support some advanced features or configurations.



To choose a Ruby serial port library, you should consider your needs and preferences. For example, if you need a simple and cross-platform solution that does not require any native compilation or installation, you may prefer rubyserial. If you need low-level access to the signals on the line or support for older Ruby versions or implementations, you may prefer serialport or serialport-pure.


How to Run a Ruby Serial Port Example




To run a Ruby serial port example, you need to have a Ruby serial port library installed, a device that can communicate over a serial port, and a suitable cable to connect them. You also need to know the port identifier and the configuration parameters for your device. Here are some steps to follow:


  • Install a Ruby serial port library, such as serialport, rubyserial, or serialport-pure. You can use the gem install command or add it to your Gemfile and run bundle install.



  • Connect your device to your computer using a suitable cable. For example, if you are using an Arduino board, you can use a USB cable.



  • Find out the port identifier and the configuration parameters for your device. You can use the dmesg command or the Device Manager to find out the port identifier. You can check the documentation or the source code of your device to find out the configuration parameters, such as baud rate, data bits, stop bits, parity, and flow control.



  • Create a Ruby file with the code that uses the serial port library to communicate with your device. For example, you can use the following code that uses the serialport gem to read and write data from an Arduino board:



require 'serialport'


ser = SerialPort.new("/dev/ttyACM0", 9600) # change this to match your port and baud rate


ser.write("Hello, Arduino!") # write a string


data = ser.readline # read a line


puts data # print the data


ser.close # close the port


This code creates a SerialPort object with the port identifier and the baud rate as arguments. It then writes a string to the serial port and reads a line from it. It prints the data and closes the port.


  • Run the Ruby file with the ruby command. You should see the output of your device on your terminal. For example, if you are using an Arduino sketch that echoes data from serial port, you should see something like this:



$ ruby serial_example.rb


Hello, Arduino!


This means that your Ruby code successfully communicated with your device over a serial port.


Conclusion




In this article, you learned how to use Ruby to read data from serial port. You learned what a serial port is, how to install and use a Ruby serial port library, how to create and configure a SerialPort object, how to read and write data from a serial port, how to handle errors and exceptions, how to choose a Ruby serial port library, and how to run a Ruby serial port example. You also learned some tips and tricks for working with serial ports in Ruby.


Serial port communication is a useful skill for interacting with various devices and applications. With Ruby, you can easily and quickly create scripts and programs that can communicate with serial ports. You can use the Ruby IO methods and the serial port libraries to access and control serial ports in a cross-platform and consistent way. You can also leverage the power and expressiveness of Ruby to create complex and creative applications that use serial ports.


We hope you enjoyed this article and learned something new. If you have any questions or feedback, please feel free to leave a comment below. Happy coding! b99f773239


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