Class: SerialProtocol::RCA2006

Inherits:
Object
  • Object
show all
Defined in:
lib/protocol/rca2006.rb

Overview

Serial protocol Roboterclub Aachen 2006 www.roboterclub.rwth-aachen.de/

Packet format:

[0x65, 0xEB, <type:8>, <counter:8>, <length:8>, data:length>, <crc:16>]

<type> is one of the following:

0b00000000 --> Data packet, discard on checksum mismatch
0b00011111 --> Data packet, resend on checksum mismatch
0b11100011 --> ACK packet
0b11111100 --> NACK packet

Direct Known Subclasses

RCA2006Simple

Constant Summary collapse

STARTBYTES = 
"\x65\xeb"
TYPE = 
{
:data_no_crc => 0, 
:data        => 0b00011111, 
:ack         => 0b11100011, 
:nack        => 0b11111100 }

Instance Method Summary collapse

Constructor Details

#initialize(send_callback, receive_callback, options = {}) ⇒ RCA2006

Returns a new instance of RCA2006.



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# File 'lib/protocol/rca2006.rb', line 24

def initialize(send_callback, receive_callback, options = {})
  @rec_queue = Queue.new
  @state = :first_startbyte
  @send_callback = send_callback
  @receive_callback = receive_callback
end

Instance Method Details

#add_char_to_packet(char) ⇒ Object

Big and ugly state machine that does most of the work



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# File 'lib/protocol/rca2006.rb', line 74

def add_char_to_packet(char)
  @state = :first_checksum if (@state == 0)
  case @state
  when :first_startbyte
    @data = ""
    @state = ((char == STARTBYTES[0]) ? :second_startbyte : :first_startbyte)
  when :second_startbyte
    @state = (char == STARTBYTES[1]) ? :type : 
      # special case: first startbyte is repeated
      (char == STARTBYTES[0] ? :second_startbyte : :first_startbyte)
  when :type
    @type = TYPE.invert[char]
    @state = :counter
  when :counter
    @counter = char
    @state = :length
  when :length
    @length = char
    @state = @length
  when Integer
    @data << char
    @state -= 1
  when :first_checksum
    @checksum = (char << 8)
    @state = :second_checksum
  when :second_checksum
    @checksum = @checksum + char
    @state = :first_startbyte

    crc = ("" << @counter << @length << @data).crc_xmodem
      # received a valid packet
      
    if @type == :data || @type == :data_no_crc
      if @checksum == crc
         
        # send ACK
        send_packet(nil, :type => :ack, :counter => @counter)
        receive_handler(@type, @counter, @data,@checksum)
      else
        # send NACK and discard packet
        send_packet(nil, :type => :nack, :counter => @counter)
        raise ChecksumMismatch, "ChecksumMismatch, expected #{crc}, was #{@checksum}"
      end
    else
      # the packet is ACK, NACK or unknown, call receive-handler
      # data may be mangled since the checksum is not checked
      #
      receive_handler(@type, @counter, @data, @checksum)
    end
  end        
end

#on_raw_receive(&block) ⇒ Object

Set callbacks whenever a packet is sent or received.



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# File 'lib/protocol/rca2006.rb', line 33

def on_raw_receive(&block)
  @raw_receive_callback = block
end

#on_raw_send(&block) ⇒ Object 



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# File 'lib/protocol/rca2006.rb', line 36

def on_raw_send(&block)
  @raw_send_callback = block
end

#receive_handler(type, counter, data, checksum) ⇒ Object 



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# File 'lib/protocol/rca2006.rb', line 59

def receive_handler(type, counter, data, checksum)
  @raw_receive_callback.call(type,counter,data,checksum) if @raw_receive_callback
  
  case type
  when :ack
  when :nack
  when :data
    @receive_callback.call(data)
  when :data_no_crc
    @receive_callback.call(data)
  end
end

#send_packet(data, options = {}) ⇒ Object

Wrap a string into a packet

the options-hash can be used to override the default packet format



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# File 'lib/protocol/rca2006.rb', line 44

def send_packet(data, options = {})
  str = data.to_s
  type = TYPE[ options[:type] || :data_no_crc].chr
  counter = options[:counter] || 0
  checksum = options[:checksum] || ("" << counter << str.length << str).crc_xmodem

  @raw_send_callback.call(type, counter, data, checksum) if @raw_send_callback
  
  p = "" << STARTBYTES << type << counter << str.length << str << [checksum].pack("S").reverse

  # send the packet, using the callback
  #
  @send_callback.call(p)
end