Module: Beaglebone::AIN

Defined in:
lib/beaglebone/ain.rb

Overview

AIN

procedural methods for Analog Input

Summary

#read is called to get the analog value of a pin. More advanced polling methods are also available

Constant Summary collapse

RANGE =

valid voltage readings in mv

(0..1799)

Class Method Summary collapse

Class Method Details

.cleanup ⇒ Object

Disable all analog pins



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# File 'lib/beaglebone/ain.rb', line 346

def cleanup
  #reset all GPIO we've used to IN and unexport them
  get_analog_pins.each { |x| disable_analog_pin(x) }
end

.disable_analog_pin(pin) ⇒ Object

Disable an analog pin

Parameters:

  • pin —

    should be a symbol representing the header pin



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# File 'lib/beaglebone/ain.rb', line 340

def disable_analog_pin(pin)
  Beaglebone::check_valid_pin(pin, :analog)
  Beaglebone::delete_pin_status(pin)
end

.get_analog_pins ⇒ Array<Symbol>

Return an array of AIN pins in use

AIN.get_analog_pins => [:P9_33, :P9_34]

Returns:

  • (Array<Symbol>) 


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# File 'lib/beaglebone/ain.rb', line 333

def get_analog_pins
  Beaglebone.pinstatus.clone.select { |x,y| x if y[:type] == :analog}.keys
end

.read(pin) ⇒ Integer

Read from an analog pin

Examples:

AIN.read(:P9_33) => 1799

Parameters:

  • pin —

    should be a symbol representing the header pin

Returns:

  • (Integer) —

    value in millivolts



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# File 'lib/beaglebone/ain.rb', line 23

def read(pin)
  Beaglebone::check_valid_pin(pin, :analog)

  Beaglebone::set_pin_status(pin, :type, :analog)

  ain_fd = Beaglebone::get_pin_status(pin, :fd_ain)

  unless ain_fd
    #ensure dtb is loaded
    Beaglebone::device_tree_load(TREES[:ADC][:global])

    #open the AIN analog input file
    pininfo = PINS[pin]

    ain_file = Dir.glob("/sys/devices/ocp.*/helper.*/AIN#{pininfo[:analog]}").first
    #ain_file = Dir.glob("/sys/bus/iio/devices/iio:device0/in_voltage#{pininfo[:analog]}_raw").first
    ain_fd = File.open(ain_file, 'r')

    Beaglebone::set_pin_status(pin, :fd_ain, ain_fd)
  end

  ain_fd.rewind
  ain_fd.read.strip.to_i
end

.run_on_change(callback, pin, mv_change = 10, interval = 0.01, repeats = nil) ⇒ Object

Runs a callback after voltage changes by specified amount. This creates a new thread that runs in the background and polls at specified interval.

Examples:

This polls every 0.1 seconds and will run after a 10mv change is detected
callback = lambda { |pin, mv_last, mv, count| puts "[#{count}] #{pin} #{mv_last} -> #{mv}" }
AIN.run_on_change(callback, :P9_33, 10, 0.1)

Parameters:

  • callback —

    A method to call when the change is detected. This method should take 4 arguments: the pin, the previous voltage, the current voltage, and the counter

  • pin —

    should be a symbol representing the header pin, i.e. :P9_11

  • mv_change (defaults to: 10) —

    an integer specifying the required change in mv

  • interval (defaults to: 0.01) —

    a number representing the wait time between polling

  • repeats (defaults to: nil) —

    is optional and specifies the number of times the callback will be run

Raises:

  • (StandardError) 


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# File 'lib/beaglebone/ain.rb', line 61

def run_on_change(callback, pin, mv_change=10, interval=0.01, repeats=nil)

  raise StandardError, "Already waiting for change on pin: #{pin}" if Beaglebone::get_pin_status(pin, :waiting)
  raise StandardError, "Already waiting for thread on pin: #{pin}" if Beaglebone::get_pin_status(pin, :thread)

  thread = Thread.new(callback, pin, mv_change, interval, repeats) do |c, p, mvc, i, r|
    begin
      count = 0
      mvl = nil
      loop do

        mvl,mv,itr = wait_for_change(p, mvc, i, mvl)

        c.call(p, mvl, mv, count) if c

        #if there was no delay in the wait_for_change, delay now.
        sleep(interval) if itr == 0

        mvl = mv
        count += 1
        break if r && count >= r
      end
    rescue => ex
      puts ex
      puts ex.backtrace
    ensure
      Beaglebone::delete_pin_status(p, :thread)
      Beaglebone::delete_pin_status(p, :waiting)
    end
  end

  Beaglebone::set_pin_status(pin, :thread, thread)
end

.run_on_threshold(callback, pin, mv_lower, mv_upper, mv_reset = 10, interval = 0.01, repeats = nil) ⇒ Object

Runs a callback after voltage changes beyond a certain threshold. This creates a new thread that runs in the background and polls at specified interval. When the voltage crosses the specified thresholds the callback is run.

Examples:

# This polls every 0.01 seconds and will run after a the voltage crosses 400mv or 1200mv.
Voltage will have to cross a range by at least 5mv to prevent rapidly triggering events
callback = lambda { |pin, mv_last, mv, state_last, state, count|
  puts "[#{count}] #{pin} #{state_last} -> #{state}     #{mv_last} -> #{mv}"
}
AIN.run_on_threshold(callback, :P9_33, 400, 1200, 5, 0.01)

Parameters:

  • callback —

    A method to call when the change is detected. This method should take 6 arguments: the pin, the previous voltage, the current voltage, the previous state, the current state, and the counter

  • pin —

    should be a symbol representing the header pin, i.e. :P9_11

  • mv_lower —

    an integer specifying the lower threshold voltage

  • mv_upper —

    an integer specifying the upper threshold voltage

  • mv_reset (defaults to: 10) —

    an integer specifying the range in mv required to reset the threshold trigger

  • interval (defaults to: 0.01) —

    a number representing the wait time between polling

  • repeats (defaults to: nil) —

    is optional and specifies the number of times the callback will be run

Raises:

  • (StandardError) 


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# File 'lib/beaglebone/ain.rb', line 120

def run_on_threshold(callback, pin, mv_lower, mv_upper, mv_reset=10, interval=0.01, repeats=nil)

  raise StandardError, "Already waiting for change on pin: #{pin}" if Beaglebone::get_pin_status(pin, :waiting)
  raise StandardError, "Already waiting for thread on pin: #{pin}" if Beaglebone::get_pin_status(pin, :thread)

  thread = Thread.new(callback, pin, mv_lower, mv_upper, mv_reset, interval, repeats) do |c, p, mvl, mvu, mvr, i, r|
    begin
      count = 0
      mv_last = nil
      state_last = nil
      loop do

        mv_last,mv,state_last,state,itr = wait_for_threshold(p, mvl, mvu, mvr, i, mv_last, state_last)

        c.call(p, mv_last, mv, state_last, state, count) if c

        #if there was no delay in the wait_for_change, delay now.
        sleep(interval) if itr == 0

        mv_last = mv
        state_last = state
        count += 1
        break if r && r >= count
      end
    rescue => ex
      puts ex
      puts ex.backtrace
    ensure
      Beaglebone::delete_pin_status(p, :thread)
      Beaglebone::delete_pin_status(p, :waiting)
    end
  end

  Beaglebone::set_pin_status(pin, :thread, thread)
end

.run_once_on_change(callback, pin, mv_change = 10, interval = 0.01) ⇒ Object

Runs a callback once after specified change in voltage detected Convenience method for run_on_change

See Also:

  • #run_on_change


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# File 'lib/beaglebone/ain.rb', line 98

def run_once_on_change(callback, pin, mv_change=10, interval=0.01)
  run_on_change(callback, pin, mv_change, interval, 1)
end

.run_once_on_threshold(callback, pin, mv_lower, mv_upper, mv_reset = 10, interval = 0.01) ⇒ Object

Runs a callback once after voltage crosses a specified threshold. Convenience method for run_on_threshold

See Also:

  • #run_on_threshold


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# File 'lib/beaglebone/ain.rb', line 159

def run_once_on_threshold(callback, pin, mv_lower, mv_upper, mv_reset=10, interval=0.01)
  run_on_threshold(callback, pin, mv_lower, mv_upper, mv_reset, interval, 1)
end

.stop_wait(pin) ⇒ Object

Stops any threads waiting for data on specified pin

Parameters:

  • pin —

    should be a symbol representing the header pin, i.e. :P9_11



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# File 'lib/beaglebone/ain.rb', line 320

def stop_wait(pin)
  thread = Beaglebone::get_pin_status(pin, :thread)

  thread.exit if thread
  thread.join if thread
end

.wait_for_change(pin, mv_change, interval, mv_last = nil) ⇒ Object

Returns when voltage changes by specified amount

Examples:

# This will poll every P9_33 every 0.01 seconds until 10mv of change is detected
# This method will return the initial reading, final reading, and how many times it polled
AIN.wait_for_change(:P9_33, 10, 0.01) => [ 1200, 1210, 4]

Parameters:

  • pin —

    should be a symbol representing the header pin, i.e. :P9_11

  • mv_change —

    an integer specifying the required change in mv

  • interval —

    a number representing the wait time between polling

  • mv_last (defaults to: nil) —

    is optional and specifies the voltage to use as the initial point to measure change

Raises:

  • (ArgumentError) 


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# File 'lib/beaglebone/ain.rb', line 275

def wait_for_change(pin, mv_change, interval, mv_last=nil)

  Beaglebone::check_valid_pin(pin, :analog)
  raise ArgumentError, "mv_change needs to be between 0 and 1800: #{pin} (#{mv_change})" unless (0..1800).include?(mv_change)

  #ensure we're the only ones waiting for this trigger
  if Beaglebone::get_pin_status(pin, :thread) && Beaglebone::get_pin_status(pin, :thread) != Thread.current
    raise StandardError, "Already waiting for change on pin: #{pin}"
  end

  if Beaglebone::get_pin_status(pin, :waiting) && Beaglebone::get_pin_status(pin, :thread) != Thread.current
    raise StandardError, "Already waiting for change on pin: #{pin}"
  end


  Beaglebone::set_pin_status(pin, :waiting, true)
  mv_last = read(pin) unless mv_last

  change_max = [mv_last - 0, 1799 - mv_last].max

  mv_change = change_max if mv_change > change_max

  count = 0
  loop do
    mv = read(pin)

    #if we've detected the change or hit the edge of the range
    if (mv - mv_last).abs >= mv_change

      Beaglebone::delete_pin_status(pin, :waiting)
      return [ mv_last, mv, count ]
    end

    sleep interval

    count += 1
  end

  Beaglebone::delete_pin_status(pin, :waiting)
  [ mv_last, -1, count ]
end

.wait_for_threshold(pin, mv_lower, mv_upper, mv_reset = 10, interval = 0.01, mv_last = nil, state_last = nil) ⇒ Object

Runs a callback after voltage changes beyond a certain threshold. This creates a new thread that runs in the background and polls at specified interval. When the voltage crosses the specified thresholds the callback is run.

This method should take 6 arguments: the pin, the previous voltage, the current voltage, the previous state, the current state, and the counter

Examples:

# This polls every 0.01 seconds and will run after a the voltage crosses 400mv or 1200mv.
# Voltage will have to cross a range by at least 5mv to prevent rapidly triggering events
callback = lambda { |pin, mv_last, mv, state_last, state, count|
  puts "[#{count}] #{pin} #{state_last} -> #{state}     #{mv_last} -> #{mv}"
}
AIN.run_on_threshold(callback, :P9_33, 400, 1200, 5, 0.01)

Parameters:

  • pin —

    should be a symbol representing the header pin, i.e. :P9_11

  • mv_lower —

    an integer specifying the lower threshold voltage

  • mv_upper —

    an integer specifying the upper threshold voltage

  • mv_reset (defaults to: 10) —

    an integer specifying the range in mv required to reset the threshold trigger

  • interval (defaults to: 0.01) —

    a number representing the wait time between polling

  • mv_last (defaults to: nil) —

    is optional and specifies the voltage to use as the initial point to measure change

  • state_last (defaults to: nil) —

    is optional and specifies the state to use as the initial state to watch change

Raises:

  • (ArgumentError) 


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# File 'lib/beaglebone/ain.rb', line 186

def wait_for_threshold(pin, mv_lower, mv_upper, mv_reset=10, interval=0.01, mv_last=nil, state_last=nil)
  Beaglebone::check_valid_pin(pin, :analog)
  raise ArgumentError, "mv_upper needs to be between 0 and 1800: #{pin} (#{mv_upper})" unless (0..1800).include?(mv_upper)
  raise ArgumentError, "mv_lower needs to be between 0 and 1800: #{pin} (#{mv_lower})" unless (0..1800).include?(mv_lower)
  raise ArgumentError, "mv_lower needs to be <= mv_upper: #{pin} (#{mv_lower}:#{mv_upper})" unless mv_lower <= mv_upper
  raise ArgumentError, "mv_reset needs to be between 0 and 1800: #{pin} (#{mv_reset})" unless (0..1800).include?(mv_reset)

  #ensure we're the only ones waiting for this trigger
  if Beaglebone::get_pin_status(pin, :thread) && Beaglebone::get_pin_status(pin, :thread) != Thread.current
    raise StandardError, "Already waiting for change on pin: #{pin}"
  end

  if Beaglebone::get_pin_status(pin, :waiting) && Beaglebone::get_pin_status(pin, :thread) != Thread.current
    raise StandardError, "Already waiting for change on pin: #{pin}"
  end

  Beaglebone::set_pin_status(pin, :waiting, true)

  mv_last = read(pin) unless mv_last

  if mv_last >= mv_upper
    state_last = :HIGH
  elsif mv_last <= mv_lower
    state_last = :LOW
  else
    state_last = :MID
  end unless state_last

  state = :UNKNOWN
  count = 0
  loop do
    mv = read(pin)

    if state_last == :LOW
      #state remains low unless it crosses into high, or above mv_low + mv_reset
      if mv >= mv_upper && mv >= mv_lower + mv_reset
        state = :HIGH
      elsif mv >= mv_lower + mv_reset
        state = :MID
      else
        state = :LOW
      end
    elsif state_last == :HIGH
      #state remains high unless it crosses into low, or below mv_high - mv_reset
      if mv <= mv_lower && mv <= mv_upper - mv_reset
        state = :LOW
      elsif mv <= mv_upper - mv_reset
        state = :MID
      else
        state = :HIGH
      end
    elsif state_last == :MID
      #state changes from normal by crossing into upper or lower
      if mv >= mv_upper
        state = :HIGH
      elsif mv <= mv_lower
        state = :LOW
      else
        state = :MID
      end
    end

    #if we've detected a change of state
    if state != state_last
      Beaglebone::delete_pin_status(pin, :waiting)
      return [ mv_last, mv, state_last, state, count ]
    end

    sleep interval

    count += 1
  end

  Beaglebone::delete_pin_status(pin, :waiting)
  [ mv_last, -1, state_last, state_last, count ]

end