Class: UltrasonicComm

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

Overview

Low-level interface for communicating with the NXT’s Ultrasonic sensor. Unlike the other sensors, the Ultrasonic sensor is digital and uses the low-speed I2C protocol for communication. This is defined in Appendix 7 of the Lego Mindstorms NXT SDK.

Constant Summary collapse

@@i2c_dev = 
0x02
@@const_codes =

first value is the i2c address, second value is the expected number of bytes returned

{
  'read_version'               => [0x00, 8],
  'read_product_id'            => [0x08, 8],
  'read_sensor_type'           => [0x10, 8],
  'read_factory_zero'          => [0x11, 1],
  'read_factory_scale_factor'  => [0x12, 1],
  'read_factory_scale_divisor' => [0x13, 1],
  'read_measurement_units'     => [0x14, 7],
}
@@var_codes =

value is the i2c address (all of these ops always expect to return 1 byte)

{  
  'read_continuous_measurements_interval' => 0x40,
  'read_command_state'                    => 0x41,
  'read_measurement_byte_0'               => 0x42,
  'read_measurement_byte_1'               => 0x43,
  'read_measurement_byte_2'               => 0x44,
  'read_measurement_byte_3'               => 0x45,
  'read_measurement_byte_4'               => 0x46,
  'read_measurement_byte_5'               => 0x47,
  'read_measurement_byte_6'               => 0x48,
  'read_measurement_byte_7'               => 0x49,
  'read_actual_zero'                      => 0x50,
  'read_actual_scale_factor'              => 0x51,
  'read_actual_scale_divisor'             => 0x52,
}
@@cmd_codes =

first value is the i2c address, second value is the command

{
  'off_command'                         => [0x41, 0x00],
  'single_shot_command'                 => [0x41, 0x01],
  'continuous_measurement_command'      => [0x41, 0x02],
  'event_capture_command'               => [0x41, 0x03],
  'request_warm_reset'                  => [0x41, 0x04],
  'set_continuous_measurement_interval' => [0x40],
  'set_actual_zero'                     => [0x50],
  'set_actual_scale_factor'             => [0x51],
  'set_actual_scale_divisor'            => [0x52]
}

Class Method Summary collapse

Class Method Details

.method_missing(name, *args) ⇒ Object 



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# File 'lib/ultrasonic_comm.rb', line 72

def self.method_missing(name, *args)
  name = name.to_s
  if @@const_codes.has_key? name
    type = :const
    op = @@const_codes[name]
    addr = op[0]
    rx_len = op[1]
  elsif @@var_codes.has_key? name
    type = :var
    op = @@var_codes[name]
    addr = op
    rx_len = 1
  elsif @@cmd_codes.has_key? name
    type = :cmd
    op = @@cmd_codes[name]
    addr = op[0]
    if op[1] then value = op[1]
    elsif args[0] then value = args[0]
    else raise "Missing argument for command #{name}" end
    rx_len = 0
  else
    raise "Unknown ultrasonic sensor command: #{name}"
  end

  data = [@@i2c_dev, addr]
  data += [value] if type == :cmd
  
  [data.size, rx_len] + data
end

.read_measurement_byte(num) ⇒ Object 



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# File 'lib/ultrasonic_comm.rb', line 68

def self.read_measurement_byte(num)
  eval "self.read_measurement_byte_#{num}"
end