diff --git a/biju.gemspec b/biju.gemspec
index 5798961..ddce90a 100644
--- a/biju.gemspec
+++ b/biju.gemspec
@@ -15,8 +15,8 @@ Gem::Specification.new do |gem|
   gem.require_paths = ["lib"]
   gem.version       = Biju::VERSION
 
-  gem.add_development_dependency "minitest",    "3.0.0"
+  gem.add_development_dependency "rspec", "~> 2.14.0"
 
-  gem.add_dependency "serialport",              ">=1.0.4"
+  gem.add_dependency "serialport", "~> 1.1.0"
   gem.add_dependency "parslet", "~> 1.5.0"
 end
diff --git a/lib/biju.rb b/lib/biju.rb
index 656b999..947bf99 100644
--- a/lib/biju.rb
+++ b/lib/biju.rb
@@ -1,4 +1,6 @@
 require 'biju/version'
-require "biju/modem"
-require "biju/sms"
-require "biju/hayes"
+require 'biju/modem'
+require 'biju/to_hayes'
+require 'biju/hayes'
+require 'biju/sms'
+require 'biju/parser'
diff --git a/lib/biju/hayes.rb b/lib/biju/hayes.rb
index ff5d0bb..3eacc0c 100644
--- a/lib/biju/hayes.rb
+++ b/lib/biju/hayes.rb
@@ -1,69 +1,92 @@
 module Biju
   class Hayes
-    attr_accessor :command, :attributes, :ok
-    attr_reader :answer
+    attr_reader :modem
 
-    #def method_missing(m, *args, &block)
-    #end
+    def initialize(port, options = {})
+      pin = options.delete(:pin) || '0000'
+      @modem = Modem.new(port, options)
+
+      attention
+      init_modem
+      unlock_pin pin
+
+      text_mode
+      extended_error
+    end
+
+    def at_command(cmd = nil, *args, &block)
+      command = ['AT', cmd].compact.join
+      command_args = args.compact.to_hayes
+
+      full_command = [command, (command_args.empty? ? nil : command_args)]
+        .compact.join('=')
+
+      answer = write(full_command)
+
+      return block.call(answer) if block_given?
+      answer
+    end
 
     def attention
-      at_command { |response| response =~ /OK/ }
-      #at_command { |response| true }
+      at_command[:status]
     end
 
     def init_modem
-      at_command('Z') { |response| response =~ /OK/ }
+      at_command('Z')[:status]
     end
 
     def text_mode(enabled = true)
-      at_command('+CMGF', enabled) { |response| response =~ /OK/ }
+      at_command('+CMGF', enabled)[:status]
     end
 
-    def prefered_storage?
-      at_command('+CPMS') { |response| response =~ /OK/ }
+    def extended_error(enabled = true)
+      at_command('+CMEE', enabled)[:status]
     end
 
-    def answer=(ret)
-      @answer = ret
-      ok?
+    def prefered_storage(pms = nil)
+      result = at_command('+CPMS', pms)
+      return result[:array] if result[:cmd] == '+CPMS'
+      nil
     end
 
-    def ok?
-      ok.nil? ? true : !ok.call(answer).nil?
+    def unlock_pin(pin)
+      at_command('+CPIN', pin)[:status]
+    end
+
+    def messages(which = "ALL")
+      prefered_storage 'MT'
+      sms = at_command('+CMGL', which)
+
+      return sms[:status] if !sms.has_key?(:sms) || sms[:sms].empty?
+      sms[:sms].map do |msg|
+        Biju::Sms.new(
+          id: msg[:infos][0],
+          phone_number: msg[:infos][2],
+          datetime: msg[:infos][4],
+          message: msg[:message].chomp)
+      end
+    end
+
+    # Delete a sms message by id.
+    # @param [Fixnum] Id of sms message on modem.
+    def delete(id)
+      at_command('+CMGD', id)
+    end
+
+    def send(sms, options = {})
+      at_command('+CMGS', sms.phone_number)
+      write("#{sms.message}#{26.chr}")
     end
 
     private
 
-    def at_command(cmd = nil, *args, &block)
-      option_prefix = nil #options[:prefix] || nil
-      cmd_root = ['AT', cmd].compact.join(option_prefix)
-      cmd_args = args.compact.map { |arg| to_hayes_string(arg) } unless args.empty?
-      self.command = [cmd_root, cmd_args].compact.join('=')
-      self.ok = block if block_given?
-      command
+    def write(text)
+      modem.write(text)
+      hayes_to_obj(modem.wait_answer)
     end
 
     def hayes_to_obj(str)
-    end
-
-    # OPTIMIZE : add () to array
-    def to_hayes_string(arg)
-      case arg
-      when String
-        "\"#{arg}\""
-      when Array
-        arg.join(',')
-      when TrueClass, FalseClass
-        !!arg ? 1 : 0
-      else
-        "?"
-      end
-    end
-  end
-
-  class HayesSms < Hayes
-    def unlock_pin(pin)
-      at_command("+CPIN=#{to_hayes_string(pin)}") { |response| response =~ /OK/ }
+      ATTransform.new.apply(ATParser.new.parse(str))
     end
   end
 end
diff --git a/lib/biju/modem.rb b/lib/biju/modem.rb
index b55f2b8..a46e432 100644
--- a/lib/biju/modem.rb
+++ b/lib/biju/modem.rb
@@ -1,36 +1,19 @@
 require 'serialport'
-require_relative 'sms'
 
 module Biju
   class Modem
+    DEFAULT_OPTIONS = { baud: 9600, data_bits: 8,
+                        stop_bits: 1, parity: SerialPort::NONE }
+
     attr_reader :connection
 
     # @param [Hash] Options to serial connection.
     # @option options [String] :port The modem port to connect
     #
-    #   Biju::Modem.new(:port => '/dev/ttyUSB0')
+    #   Biju::Modem.new('/dev/ttyUSB0')
     #
-    def initialize(options={}, &block)
-      raise Exception.new("Port is required") unless options[:port]
-      pin = options[:pin] || '0000'
-      @connection = connect(options)
-      cmd("AT")
-      # initialize modem
-      cmd("ATZ")
-      # unlock pin code
-      cmd("AT+CPIN=\"#{pin}\"") if pin
-
-      cmd("AT+CPMS=?")
-
-      # set SMS text mode
-      cmd("AT+CMGF=1")
-      # set extended error reports
-      cmd('AT+CMEE=1')
-      #instance_eval &block if block_given?
-      if block_given?
-        yield connection
-        close
-      end
+    def initialize(port, options = {})
+      @connection = SerialPort.new(port, DEFAULT_OPTIONS.merge!(options))
     end
 
     # Close the serial connection.
@@ -38,59 +21,16 @@ module Biju
       connection.close
     end
 
-    # Return an Array of Sms if there is messages nad return nil if not.
-    def messages(which = "ALL")
-      # read message from all storage in the mobile phone (sim+mem)
-      cmd('AT+CPMS="MT"')
-      # get message list
-      sms = cmd('AT+CMGL="%s"' % which )
-      # collect messages
-      msgs = sms.scan(/\+CMGL\:\s*?(\d+)\,.*?\,\"(.+?)\"\,.*?\,\"(.+?)\".*?\n(.*)/)
-      return nil unless msgs
-      msgs.collect!{ |msg| Biju::Sms.new(:id => msg[0], :phone_number => msg[1], :datetime => msg[2], :message => msg[3].chomp) }
+    def write(text)
+      connection.write(text + "\r")
     end
 
-    # Delete a sms message by id.
-    # @param [Fixnum] Id of sms message on modem.
-    def delete(id)
-      cmd("AT+CMGD=#{id}")
-    end
-
-    def send(sms, options = {})
-      # initiate the sms, and wait for either
-      # the text prompt or an error message
-      cmd("AT+CMGS=\"#{sms.phone_number}\"")
-
-      # send the sms, and wait until
-      # it is accepted or rejected
-      cmd("#{sms.message}#{26.chr}")
-      # ... check reception
-    end
-
-    private
-    def connect(options)
-      port = options.delete(:port)
-      SerialPort.new(port, default_options.merge!(options))
-    end
-
-    def default_options
-      { :baud => 9600, :data_bits => 8, :stop_bits => 1, :parity => SerialPort::NONE }
-    end
-
-    def cmd(cmd)
-puts "SENDING : #{cmd}"
-      connection.write(cmd + "\r")
-      wait_str = wait
-      #p "#{cmd} --> #{wait_str}"
-    end
-
-    def wait
+    def wait_answer
       buffer = ''
       while IO.select([connection], [], [], 0.25)
-        chr = connection.getc.chr;
-        buffer += chr
+        buffer << connection.getc.chr
       end
-puts "RECEIVING : #{buffer}"
+
       buffer
     end
   end