coin_acceptor.rb

## coin_acceptor.rb
#!/usr/bin/env ruby

# A simple class for reading values from the DG600F coin acceptor sold by
# SparkFun (https://www.sparkfun.com/products/11636)
#
# The coin acceptor must be configured to send three bytes per coin; see section
# 8.6 of the manual.
#
# You can configure the serial device and baud rate, e.g.:
#
#   c = CoinAcceptor.new device: '/dev/ttyS0', baud: 2400
#
# By default it will use /dev/ttyUSB0 at 9600 baud.
#
# You must pass a block which will receive the credit value as configured
# on the coin acceptor:
#
#   c.accept_coins do |credit|
#     puts "You put in #{credit}s"
#   end
#
# For testing at the command line, you can just run this file directly.

require 'serialport'

class CoinAcceptor
  HEADER = 0xAA
  IGNORE = 0xFF

  attr_reader :serial_port

  def initialize device: "/dev/ttyUSB0", baud: 9600
    @serial_port = SerialPort.new device, baud, 8, 1, SerialPort::NONE
    @serial_port.flush_input
  end

  def get_byte
    byte = IGNORE
    byte = @serial_port.read(1).unpack('C').first until byte != IGNORE
    byte
  end

  def accept_coins
    loop do
      if get_byte == HEADER
        credit = get_byte
        check  = get_byte
        yield credit if check == HEADER ^ credit
      end
    end
  end
end

if __FILE__ == $0
  c = CoinAcceptor.new

  c.accept_coins do |credit|
    puts credit
  end
end