Class: OpenC3::CobsProtocol

Inherits:
TerminatedProtocol show all
Defined in:
lib/openc3/interfaces/protocols/cobs_protocol.rb

Overview

Usage in plugin.txt:

INTERFACE …

PROTOCOL READ_WRITE CobsProtocol

Instance Attribute Summary

Attributes inherited from Protocol

#allow_empty_data, #extra, #interface

Instance Method Summary collapse

Methods inherited from BurstProtocol

#handle_sync_pattern, #log_discard, #reduce_to_single_packet, #reset, #write_packet

Methods inherited from Protocol

#connect_reset, #disconnect_reset, #post_write_interface, #protocol_cmd, #read_packet, #reset, #write_packet

Constructor Details

#initialize(allow_empty_data = nil) ⇒ CobsProtocol

Returns a new instance of CobsProtocol.

Parameters:

  • allow_empty_data (true/false/nil) (defaults to: nil) —

    See Protocol#initialize



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# File 'lib/openc3/interfaces/protocols/cobs_protocol.rb', line 38

def initialize(allow_empty_data = nil)

  strip_read_termination = true
  discard_leading_bytes = 0
  sync_pattern = nil
  fill_fields = false # Handled in write_data below

  super(
    "", # Write termination handled in write_data below
    "00",
    strip_read_termination,
    discard_leading_bytes,
    sync_pattern,
    fill_fields,
    allow_empty_data
  )
end

Instance Method Details

#read_data(data, extra = nil) ⇒ Object 



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# File 'lib/openc3/interfaces/protocols/cobs_protocol.rb', line 56

def read_data(data, extra = nil)
  data, extra = super(data, extra)
  return data, extra if data.length <= 0 or Symbol === data

  result_data = ''
  while data.length > 1
    # Read the offset to the next zero byte
    # Note: This may be off the end of the data. If so, the packet is over
    zero_offset = data[0].unpack('C')[0]
    if zero_offset == 0xFF # No zeros in this segment
      result_data << data[1..254]
      data = data[255..-1]
    elsif zero_offset <= 1 # End of data or 1 zero
      result_data << "\x00"
      data = data[1..-1]
    else # Mid range zero or end of packet
      result_data << data[1..(zero_offset - 1)]
      data = data[zero_offset..-1]
      result_data << "\x00" if data.length >= 1
    end
  end

  return result_data, extra
end

#write_data(data, extra = nil) ⇒ Object 



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# File 'lib/openc3/interfaces/protocols/cobs_protocol.rb', line 81

def write_data(data, extra = nil)
  # Intentionally not calling super()

  need_insert = false
  result_data = ''
  while data.length > 0
    index = data.index("\x00")
    if (index and index > 253) or (index.nil? and data.length >= 254)
      result_data << "\xFF"
      result_data << data[0..253]
      data = data[254..-1]
      need_insert = false
    else # index <= 253 or (index.nil? and data.length < 254)
      if index
        result_data << [index + 1].pack('C')
        if index >= 1
          result_data << data[0..(index - 1)]
        end
        data = data[(index + 1)..-1]
        need_insert = true
      else
        result_data << [data.length + 1].pack('C')
        result_data << data
        data = ''
        need_insert = false
      end
    end
  end

  # Handle a zero at the end of the packet
  result_data << "\x01" if need_insert

  # Terminate message with 0x00
  result_data << "\x00"

  return result_data, extra
end