Class: ObjectOrientedBeagleboneBlack::Pwm

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

Defined Under Namespace

Modules: Polarity

Constant Summary collapse

PWM_DEVICE_TREE_OVERLAY_PARAMETER = 
"am33xx_pwm"

Instance Method Summary collapse

Constructor Details

#initialize(pin_key) ⇒ Pwm

Returns a new instance of Pwm.



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 13

def initialize(pin_key)
  @pin_key = pin_key
  @slots_file_path = File.join(File.join(OBJECT_ORIENTED_BEAGLEBONE_BLACK_CONFIG["slots_directory"], "slots"))

  activate_device_tree_overlays
end

Instance Method Details

#activate_device_tree_overlays ⇒ Object 



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 20

def activate_device_tree_overlays
  # Note: Since slots file acts as an interface to activate Device Tree Overlay, simply writing to it does what needs to be done. 
  #       I'm using appending here so that testing in a local environment becomes straightfoward. 

  puts "This can take several seconds for necessary setups..."

  slots_file = File.open(@slots_file_path, "a+")
  slots_file_content = slots_file.read

  unless slots_file_content.include? PWM_DEVICE_TREE_OVERLAY_PARAMETER
  # until slots_file_content.include? PWM_DEVICE_TREE_OVERLAY_PARAMETER

    # Just in case where the previous read session is not fully completed.
    sleep 1

    slots_file.write(PWM_DEVICE_TREE_OVERLAY_PARAMETER)

    # It seems to take a time to load the device tree overlay. Wait for two seconds.
    sleep 2

    # Note: Sometime, the file pointer seems to be at the end of the file and doesn't read the file content before that. 
    # slots_file_content = slots_file.read

  end

  # Note: Closing this file sometimes causes an error in BeagleBone Black:
  #   Errno::ENOENT: No such file or directory @ fptr_finalize - /sys/devices/bone_capemgr.9/slots
  begin
    slots_file.close if File.exist?(@slots_file_path) && !slots_file.closed?
  rescue SystemCallError => system_call_error_message
    puts "Error happened while closing #{@slots_file_path} with the message: #{system_call_error_message}"
  end

  # Just in case
  sleep 1

  puts "First step of setups done."

  pwm_pin_device_tree_overlay_parameter = "bone_pwm_#{@pin_key}"

  slots_file = File.open(@slots_file_path, "a+")
  slots_file_content = slots_file.read

  unless slots_file_content.include? pwm_pin_device_tree_overlay_parameter
  # until slots_file_content.include? pwm_pin_device_tree_overlay_parameter

    # Just in case where the previous read session is not fully completed.
    sleep 1

    slots_file.write(pwm_pin_device_tree_overlay_parameter)

    # It seems to take a time to load the device tree overlay. Wait for one second.
    sleep 2

    # Note: Sometime, the file pointer seems to be at the end of the file and doesn't read the file content before that.
    # slots_file_content = slots_file.read

  end

  # Note: Closing this file sometimes causes an error in BeagleBone Black:
  #   Errno::ENOENT: No such file or directory @ fptr_finalize - /sys/devices/bone_capemgr.9/slots
  begin
    slots_file.close if File.exist?(@slots_file_path) && !slots_file.closed?
  rescue SystemCallError => system_call_error_message
    puts "Error happened while closing #{@slots_file_path} with the message: #{system_call_error_message}"
  end

  puts "Setups done."

end

#duty_cycle ⇒ Object 



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 98

def duty_cycle
  # Using this instead of simple "File.open(file_path).read" in order to close file after reading.
  internal_duty_value = nil
  File.open(File.join(pwm_directory, "duty"), "r") { |file| internal_duty_value = file.read.strip }
  duty_cycle = (BigDecimal(internal_duty_value.to_s) / BigDecimal(period.to_s)).to_f
  duty_cycle
end

#duty_cycle=(duty_cycle) ⇒ Object

duty_cycle (value between 0 and 1)



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 92

def duty_cycle=(duty_cycle)
  self.polarity = ObjectOrientedBeagleboneBlack::Pwm::Polarity::DIRECT
  internal_duty_value = (BigDecimal(duty_cycle.to_s) * BigDecimal(period.to_s)).to_i
  File.open(File.join(pwm_directory, "duty"), "w") { |file| file.write(internal_duty_value) }
end

#period ⇒ Object

Unit: [ns] (nano second)



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 128

def period
  internal_period_value = nil
  File.open(File.join(pwm_directory, "period"), "r") { |file| internal_period_value = file.read.strip.to_i }
  internal_period_value
end

#period=(period) ⇒ Object 



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 116

def period=(period)
  current_duty_cycle = self.duty_cycle

  File.open(File.join(pwm_directory, "period"), "w") { |file| file.write(period) }
  
  # Preserves the duty cycle:
  # Note: Internally in BeagleBone Black, "duty" value is relative to "period" value. 
  #       e.g. For "period" = 1000, "duty" = 500 gives the duty cycle = 500 / 1000 = 0.5.
  self.duty_cycle = current_duty_cycle
end

#polarity ⇒ Object 



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 110

def polarity
  internal_polarity_value = nil
  File.open(File.join(pwm_directory, "polarity"), "r") { |file| internal_polarity_value = file.read.strip.to_i }
  internal_polarity_value
end

#polarity=(polarity) ⇒ Object 



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# File 'lib/object_oriented_beaglebone_black/pwm.rb', line 106

def polarity=(polarity)
  File.open(File.join(pwm_directory, "polarity"), "w") { |file| file.write(polarity) }
end