FFI Serial

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

Why?

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

Why IO?

• 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

Why FFI?

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

Installation

gem install ffi-serial

Usage

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

Notes

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.