yamaha-receiver.rb

# Watch Yamaha AV receivers for events
#
# This script watches a Yamaha AV receiver for changes in state.
# It also implements two functions for changing the volume which is a fun
# way to "help" unsuspecting users.
#
# Protocol is here: https://www.sdu.se/pub/yamaha/yamaha-ynca-receivers-protocol.pdf

require "socket"
require "io/wait"
require "logger"

def volume s
  s.write "@MAIN:VOL=?\r\n"
  s.gets.split('=').last.to_f
end

def set_volume s, to
  s.write "@MAIN:VOL=#{sprintf("%.1f", to)}\r\n"
  s.gets.split('=').last.to_f
end

logger = Logger.new $stderr

s = TCPSocket.new "yamaha-av-receiver.local", 50000
s.write "@SYS:PWR=?\r\n"
logger.info s.gets.chomp
s.write "@MAIN:PWR=?\r\n"
logger.info s.gets.chomp

loop do
  if s.wait_readable 30
    logger.info s.gets.chomp
  else
    s.write "@SYS:VERSION=?\r\n"
    logger.debug s.gets.chomp
  end
end

s.close