FFI Serial is a simple OS independent gem to allow access to a serial port

Other gems exist, why this gem?

1. Opens Serial port as Ruby IO object
2. Uses FFI to configure serial port using native operating system functions

• Serial ports are exposed as files in both Posix(Linux/Mac/BSD/etc) and Windows
• Ruby IO provides a rich API and it is part of standard library
• Ruby IO contains a large amount of very efficient and well tested code
• Reduces gem complexity to only configuring serial port

• Removes native compilation concerns
• FFI is very widely supported (portable)

gem install ffi-serial

require 'ffi-serial'

# Defaults for baud, data_bits, stop_bits and parity
port = Serial.new port: '/dev/ttyUSB0' #=> <Serial:/dev/ttyUSB0>

# Get configured settings from OS
port.baud #=> 9600
port.data_bits #=> 8
port.stop_bits #=> 1
port.parity #=> :none

# Really is a Ruby IO
port.is_a?(IO) #=> true
port.is_a?(File) #=> true

port.read_nonblock(512) #=> ... <supported in Windows>
port.readpartial(512) #=> ...
port.write "\n" #=> 1
# etc.

port.read_timeout = 1.5 #=> 1.5 # 1500ms
port.gets("\n") #=> ... Timeouts after 1.5 seconds

port.close #=> nil

# Explicit configuration (and works on Windows)
port = Serial.new port: 'COM1', data_bits: 8, stop_bits: 1, parity: :none #=> <Serial:COM1>
# OR
port = Serial.new port: 1, data_bits: 8, stop_bits: 1, parity: :none #=> <Serial:COM1>

See Ruby standard library IO for complete method list http://ruby-doc.org/core-1.9.3/IO.html

IO.read will not behave exactly as described in IO.read but probably not as most developers expect. IO.read will read either until read_timeout is reached or EOF is reached.

Serial ports are not truly files and will never reach EOF, therefore if read_timeout is 0, IO.read should be expected to block forever.