Class: Commands::UltrasonicSensor

Inherits:
Object
  • Object
show all
Includes:
Mixins::Sensor
Defined in:
lib/commands/ultrasonic_sensor.rb

Overview

Implements the “Ultrasonic Sensor” block in NXT-G

Defined Under Namespace

Classes: UnmeasurableDistance

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Mixins::Sensor

#logic, #port=

Constructor Details

#initialize(nxt) ⇒ UltrasonicSensor

Returns a new instance of UltrasonicSensor.



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# File 'lib/commands/ultrasonic_sensor.rb', line 32

def initialize(nxt)
  @nxt      = nxt
  
  # defaults the same as NXT-G
  @port           = 4
  @trigger_point  = 50
  @comparison     = "<"
  @mode           = :inches
  set_mode
end

Instance Attribute Details

#comparison ⇒ Object

Returns the value of attribute comparison.



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# File 'lib/commands/ultrasonic_sensor.rb', line 30

def comparison
  @comparison
end

#mode ⇒ Object

Returns the value of attribute mode.



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# File 'lib/commands/ultrasonic_sensor.rb', line 30

def mode
  @mode
end

#port ⇒ Object (readonly)

Returns the value of attribute port.



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# File 'lib/commands/ultrasonic_sensor.rb', line 29

def port
  @port
end

#trigger_point ⇒ Object

Returns the value of attribute trigger_point.



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# File 'lib/commands/ultrasonic_sensor.rb', line 30

def trigger_point
  @trigger_point
end

Instance Method Details

#distance ⇒ Object Also known as: value_scaled

returns distance in requested mode (:inches or :centimeters)



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# File 'lib/commands/ultrasonic_sensor.rb', line 44

def distance
  @nxt.ls_write(NXTComm.const_get("SENSOR_#{@port}"), UltrasonicComm.read_measurement_byte(0))
  
  # Keep checking until we have data to read
  while @nxt.ls_get_status(NXTComm.const_get("SENSOR_#{@port}")) < 1
    sleep(0.1)
    # TODO: implement timeout so we don't get stuck if the expected data never comes
  end
  
  distance = @nxt.ls_read(NXTComm.const_get("SENSOR_#{@port}"))[:data][0]
  
  if @mode == :centimeters
    distance.to_i
  else
   (distance * 0.3937008).to_i
  end
end

#distance! ⇒ Object

returns the distance in requested mode; raises an UnmeasurableDistance exception when the distance cannot be measured (i.e. when the distance == 255, which is the code the sensor returns when it cannot get a distance reading)

Raises:



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# File 'lib/commands/ultrasonic_sensor.rb', line 66

def distance!
  d = distance
  raise UnmeasurableDistance if d == 255
  return d
end

#set_mode ⇒ Object

sets up the sensor port



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# File 'lib/commands/ultrasonic_sensor.rb', line 73

def set_mode
  @nxt.set_input_mode(
    NXTComm.const_get("SENSOR_#{@port}"),
    NXTComm::LOWSPEED_9V,
    NXTComm::RAWMODE
  )
  # clear buffer
  @nxt.ls_read(NXTComm.const_get("SENSOR_#{@port}"))
  # set sensor to continuously send pings
  @nxt.ls_write(NXTComm.const_get("SENSOR_#{@port}"), UltrasonicComm.continuous_measurement_command)
end