Module: LittleWire::Analog

Included in:
LittleWire
Defined in:
lib/littlewire/analog.rb

Constant Summary collapse

AnalogReferences =

Read the current value of an analog input Valid inputs are

[:vcc, :internal_reference_1_1, :internal_reference_2_56]

Instance Method Summary collapse

Instance Method Details

#analog_read(input_name, voltage_reference = :vcc) ⇒ Object 



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# File 'lib/littlewire/analog.rb', line 5

def analog_read input_name, voltage_reference = :vcc
  voltage_reference = AnalogReferences.index(voltage_reference) if AnalogReferences.include? voltage_reference
  scaling_setting = 0x07
  
  if @analog_reference != voltage_reference
    @analog_reference = voltage_reference
    # This reset step is to work around a bug in firmware 1.1 - hopefully it can be disabled in future releases
    control_transfer(function: :analog_init, wValue: scaling_setting) # reset analog reference setting
    # set new reference voltage
    control_transfer(function: :analog_init, wValue: scaling_setting | voltage_reference << 8)
  end
  
  control_transfer(function: :read_adc,
                     wValue: get_pin(LittleWire::AnalogPinMap, input_name),
                     dataIn: 2).unpack('S<').first / 1024.0
end

#temperature ⇒ Object

Get the current temperature inside the LittleWire device’s microcontroller. At a courseness of about 1.1°C increments and quite a lot of noise in the measurements, some averaging is required. Rather neatly, because of the noise in each sample, when averaged you get higher than 1.1°C resolution.

This method returns a value around 280.0 - you’ll need to calibrate it yourself by simple subtraction. You can calibrate it even more accurately by linearly mapping it to two known temperature points. Each LittleWire is a bit different so some calibration is necessary (unless you just want to take relative measurements).



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# File 'lib/littlewire/analog.rb', line 29

def temperature
  (analog_read(:temperature, :internal_reference_1_1) * 1024.0) / 1.12
end