Class: Lignite::Connection::Usb

Inherits:
Lignite::Connection show all
Includes:
Logger
Defined in:
lib/lignite/connection/usb.rb

Overview

A Lignite::Connection over a USB cable

Constant Summary collapse

VENDOR_LEGO =

To get to the endpoint we need to descend down the hierarchy of 1) Device

0x0694
PRODUCT_EV3 = 
5
CONFIGURATION_EV3 =

2) Configuration, 1-based

1
INTERFACE_EV3 =

3) Interface, 0-based

0
SETTING_EV3 =

4) Alternate setting, 0-based

0
ENDPOINT_EV3 =

5) Endpoint, 0-based

1

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Logger

default_logger, #logger

Methods inherited from Lignite::Connection

create, #receive, reset, #send

Methods included from Bytes

#bin_to_hex, #f32, #hex_to_bin, #u16, #u32, #u8, #unpack_f32, #unpack_u16, #unpack_u32, #unpack_u8

Constructor Details

#initialize ⇒ Usb

Returns a new instance of Usb.

Raises:



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# File 'lib/lignite/connection/usb.rb', line 29

def initialize
  super
  usb = LIBUSB::Context.new
  @device = usb.devices(idVendor: VENDOR_LEGO, idProduct: PRODUCT_EV3).first
  raise Lignite::NoUsbDevice if @device.nil?

  ## Because multiple configs are rare, the library allows to omit this:
  ## device.set_configuration(CONFIGURATION_EV3)
  @interface = @device.interfaces[INTERFACE_EV3]
  eps = @interface.endpoints
  @out_ep = eps.find { |e| e.direction == :out }
  @in_ep = eps.find { |e| e.direction == :in }
end

Instance Attribute Details

#device ⇒ Object (readonly)

Returns the value of attribute device.



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# File 'lib/lignite/connection/usb.rb', line 27

def device
  @device
end

#in_ep ⇒ Object (readonly)

Returns the value of attribute in_ep.



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# File 'lib/lignite/connection/usb.rb', line 27

def in_ep
  @in_ep
end

#interface ⇒ Object (readonly)

Returns the value of attribute interface.



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# File 'lib/lignite/connection/usb.rb', line 27

def interface
  @interface
end

#out_ep ⇒ Object (readonly)

Returns the value of attribute out_ep.



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# File 'lib/lignite/connection/usb.rb', line 27

def out_ep
  @out_ep
end

Instance Method Details

#close ⇒ Object 



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# File 'lib/lignite/connection/usb.rb', line 73

def close
  super
  # do nothing: read and write open and close the handle each time
end

#read(bytes = nil) ⇒ String

Returns:

  • (String) 


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# File 'lib/lignite/connection/usb.rb', line 56

def read(bytes = nil)
  got = nil
  @device.open do |devh|
    devh.auto_detach_kernel_driver = true
    devh.claim_interface(@interface) do
      begin
        got = devh.interrupt_transfer(endpoint: @in_ep, dataIn: bytes)
      rescue LIBUSB::Error => e
        got = e.transferred
        raise unless got.is_a? String
      end
    end
  end
  logger.debug "Read returning #{got.bytesize} bytes"
  got
end

#write(data) ⇒ Integer

Returns number of bytes written.

Returns:

  • (Integer) —

    number of bytes written



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# File 'lib/lignite/connection/usb.rb', line 44

def write(data)
  written = nil
  @device.open do |devh|
    devh.auto_detach_kernel_driver = true
    devh.claim_interface(@interface) do
      written = devh.interrupt_transfer(endpoint: @out_ep, dataOut: data)
    end
  end
  written
end