Class: Denko::Sensor::QMP6988

Inherits:
Object
  • Object
show all
Includes:
Behaviors::Lifecycle, Behaviors::Poller, I2C::Peripheral, PressureHelper, TemperatureHelper
Defined in:
lib/denko/sensor/qmp6988.rb

Constant Summary collapse

I2C_ADDRESS = 
0x70
UPDATE_TIME = 
0.020
RESET_REGISTER = 
0xE0
RESET_COMMAND = 
0xE6
CTRL_MEAS_REGISTER = 
0xF4
STANDBY_TIME_REGISTER = 
0xF5
IIR_REGISTER = 
0xF1
CONFIG_LENGTH = 
5
DATA_REGISTER = 
0xF7
DATA_LENGTH = 
6
CALIBRATION_REGISTER = 
0xA0
CALIBRATION_LENGTH = 
25
CHIP_ID_REGISTER = 
0xD1
CHIP_ID_LENGTH = 
1
FORCED_MODE = 
0b01
NORMAL_MODE = 
0b11
STANDBY_TIMES =

Standby Times for Normal (Continuous) Mode in milliseconds

{
  1    => 0b000,
  5    => 0b001,
  50   => 0b010,
  250  => 0b011,
  500  => 0b100,
  1000 => 0b101,
  2000 => 0b110,
  4000 => 0b111,
}
OVERSAMPLE_FACTORS =

Oversample Setting Values Note: Each sensor has a separate oversample setting.

General formula:

2 ** (n-1), where n is the decimal value of the bits, up to 16x max oversampling.

{
  # 0  =>  0b000, # Sensor skipped. Value will be 0x800000.
  1  =>  0b001,
  2  =>  0b010,
  4  =>  0b011,
  8  =>  0b100,
  16 =>  0b101,
  32 =>  0b110,
  64 =>  0b111,
}
TEMPERATURE_SAMPLE_TIME =

Single sample times (in milliseconds) for each sensor, derived from datasheet examples.

0.9
PRESSURE_SAMPLE_TIME = 
0.85
IIR_COEFFICIENTS =

IIR Filter Coefficients

{
  0  =>  0b000,
  2  =>  0b001,
  4  =>  0b010,
  8  =>  0b011,
  16 =>  0b100,
  32 =>  0b101, # 0b110 and 0b111 are also valid for 16.
}
CONVERSION_FACTORS = 
{
  a1:  { A: -6.3e-03,   S: 4.3e-04 },
  a2:  { A: -1.9e-11,   S: 1.2e-10 },
  bt1: { A:  1.0e-01,   S: 9.1e-02 },
  bt2: { A:  1.2e-08,   S: 1.2e-06 },
  bp1: { A:  3.3e-02,   S: 1.9e-02 },
  b11: { A:  2.1e-07,   S: 1.4e-07 },
  bp2: { A: -6.3e-10,   S: 3.5e-10 },
  b12: { A:  2.9e-13,   S: 7.6e-13 },
  b21: { A:  2.1e-15,   S: 1.2e-14 },
  bp3: { A:  1.3e-16,   S: 7.9e-17 },
  a0:  16.0,
  b00: 16.0,
}

Constants included from Behaviors::Reader

Behaviors::Reader::READ_WAIT_TIME

Constants included from Behaviors::Lifecycle

Behaviors::Lifecycle::CALLBACK_METHODS

Constants included from I2C::Peripheral

I2C::Peripheral::I2C_FREQUENCY, I2C::Peripheral::I2C_REPEATED_START

Instance Attribute Summary collapse

Attributes included from Behaviors::Threaded

#interrupts_enabled, #thread

Attributes included from I2C::Peripheral

#i2c_frequency, #i2c_repeated_start

Attributes included from Behaviors::Component

#board, #params

Instance Method Summary collapse

Methods included from PressureHelper

#pressure, #pressure_atm, #pressure_bar

Methods included from TemperatureHelper

#temperature, #temperature_f, #temperature_k

Methods included from Behaviors::Poller

#poll, #poll_using, #stop

Methods included from Behaviors::Threaded

#enable_interrupts, included, #mruby_thread_check, #stop, #stop_thread, #threaded, #threaded_loop

Methods included from Behaviors::Reader

#read, #read_busy?, #read_nb, #read_raw, #read_using, #update

Methods included from Behaviors::Callbacks

#add_callback, #callbacks, #remove_callback, #update

Methods included from Behaviors::Lifecycle

included

Methods included from I2C::Peripheral

#address, #i2c_default, #i2c_read, #i2c_read_raw, #i2c_write

Methods included from Behaviors::BusPeripheralAddressed

#address

Methods included from Behaviors::BusPeripheral

#atomically

Methods included from Behaviors::Component

#initialize, #micro_delay

Instance Attribute Details

#calibration_data_loaded ⇒ Object (readonly)

Calibration



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# File 'lib/denko/sensor/qmp6988.rb', line 233

def calibration_data_loaded
  @calibration_data_loaded
end

#iir_coefficient ⇒ Object

Returns the value of attribute iir_coefficient.



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# File 'lib/denko/sensor/qmp6988.rb', line 113

def iir_coefficient
  @iir_coefficient
end

#pressure_samples ⇒ Object

Returns the value of attribute pressure_samples.



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# File 'lib/denko/sensor/qmp6988.rb', line 142

def pressure_samples
  @pressure_samples
end

#registers ⇒ Object (readonly)

Returns the value of attribute registers.



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# File 'lib/denko/sensor/qmp6988.rb', line 228

def registers
  @registers
end

#standby_time ⇒ Object

Returns the value of attribute standby_time.



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# File 'lib/denko/sensor/qmp6988.rb', line 122

def standby_time
  @standby_time
end

#temperature_samples ⇒ Object

Returns the value of attribute temperature_samples.



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# File 'lib/denko/sensor/qmp6988.rb', line 132

def temperature_samples
  @temperature_samples
end

Instance Method Details

#_read ⇒ Object

Reading & Processing



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# File 'lib/denko/sensor/qmp6988.rb', line 175

def _read
  if @forced_mode
    # Write CTRL_MEAS register to trigger reading, then wait for measurement.
    i2c_write [CTRL_MEAS_REGISTER, @ctrl_meas_register]
    sleep @measurement_time
  end

  # Read the data bytes.
  i2c_read(DATA_LENGTH, register: DATA_REGISTER)
end

#calculate_measurement_time ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 144

def calculate_measurement_time
  @measurement_time = (@temperature_samples.to_i * TEMPERATURE_SAMPLE_TIME) +
                     (@pressure_samples.to_i * PRESSURE_SAMPLE_TIME)
  # Add 5ms for safety and convert to seconds.
  @measurement_time = (@measurement_time + 5) * 0.001
end

#chip_id ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 165

def chip_id
  return @chip_id if @chip_id
  bytes = i2c_read_raw(1, register: CHIP_ID_REGISTER)
  @chip_id = bytes[0] if bytes
  @chip_id
end

#continuous_mode ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 158

def continuous_mode
  @ctrl_meas_register = (@ctrl_meas_register & 0b11111100) | NORMAL_MODE
  i2c_write [CTRL_MEAS_REGISTER, @ctrl_meas_register]
  @forced_mode = false
  sleep UPDATE_TIME
end

#forced_mode ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 151

def forced_mode
  @ctrl_meas_register = (@ctrl_meas_register & 0b11111100) | FORCED_MODE
  i2c_write [CTRL_MEAS_REGISTER, @ctrl_meas_register]
  @forced_mode = true
  sleep UPDATE_TIME
end

#get_calibration_data ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 250

def get_calibration_data
  bytes = i2c_read_raw(CALIBRATION_LENGTH, register: CALIBRATION_REGISTER)

  if bytes
    # These 2 values are 20-bit instead of 16-bit, so can't combine them with #pack.
    a0_unsigned  = (bytes[18] << 12) + (bytes[19] << 4) + (bytes[24] & 0b00001111)
    b00_unsigned = (bytes[0] << 12) + (bytes[1] << 4) + ((bytes[24] & 0b11110000) >> 4)

    # Cast the raw bytes as big-endian signed.
    @calibration_raw = {
      # Shift these to 32-bit before converting to signed, then reverse the shift after.
      a0: [(a0_unsigned << 12)].pack('L>').unpack('l>')[0] >> 12,
      b00: [(b00_unsigned << 12)].pack('L>').unpack('l>')[0] >> 12,

      a1: bytes[20..21].pack('C*').unpack('s>')[0],
      a2: bytes[22..23].pack('C*').unpack('s>')[0],

      b11: bytes[8..9].pack('C*').unpack('s>')[0],
      b12: bytes[12..13].pack('C*').unpack('s>')[0],
      b21: bytes[14..15].pack('C*').unpack('s>')[0],

      bp1: bytes[6..7].pack('C*').unpack('s>')[0],
      bp2: bytes[10..11].pack('C*').unpack('s>')[0],
      bp3: bytes[16..17].pack('C*').unpack('s>')[0],

      bt1: bytes[2..3].pack('C*').unpack('s>')[0],
      bt2: bytes[4..5].pack('C*').unpack('s>')[0],
    }

    # Use conversion formulae to calculate compensation coefficients, all as floats.
    @calibration = {}
    @calibration_raw.keys.each do |key|
      if CONVERSION_FACTORS[key].class == Float
        @calibration[key] = @calibration_raw[key] / CONVERSION_FACTORS[key]
      else
        @calibration[key] = CONVERSION_FACTORS[key][:A] + (CONVERSION_FACTORS[key][:S] * @calibration_raw[key] / 32767.0)
      end
    end

    @calibration_data_loaded = true
  end
end

#get_config_registers ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 222

def get_config_registers
  bytes = i2c_read_raw(CONFIG_LENGTH, register: IIR_REGISTER)
  if bytes
    @registers = { f1: bytes[0], f2: bytes[1], f3: bytes[2], f4: bytes[3], f5: bytes[4] }
  end
end

#pre_callback_filter(bytes) ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 186

def pre_callback_filter(bytes)
  return nil unless bytes.length == DATA_LENGTH

  # Temperature and pressure are 24-bits long each, and need 2^23 subtracted.
  dt = ((bytes[3] << 16) + (bytes[4] << 8) + bytes[5]) - (0b1 << 23)
  dp = ((bytes[0] << 16) + (bytes[1] << 8) + bytes[2]) - (0b1 << 23)

  # Compensated temperature calculated in 1/256 of a degree Celsius.
  tr =  @calibration[:a0] +
        @calibration[:a1] * dt +
        @calibration[:a2] * (dt ** 2)
  reading[:temperature] = tr / 256.0

  # Compensated pressure calculated in Pascals.
  reading[:pressure] =  @calibration[:b00] +
                        @calibration[:bt1] * tr +
                        @calibration[:bp1] * dp +
                        @calibration[:b11] * (tr * dp)  +
                        @calibration[:bt2] * (tr ** 2) +
                        @calibration[:bp2] * (dp ** 2) +
                        @calibration[:b12] * (dp * (tr ** 2)) +
                        @calibration[:b21] * ((dp ** 2) * tr) +
                        @calibration[:bp3] * (dp ** 3)

  # Return reading for callbacks.
  reading
end

#reading ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 96

def reading
  @reading ||= { temperature: nil, pressure: nil }
end

#reset ⇒ Object

Configuration Methods



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# File 'lib/denko/sensor/qmp6988.rb', line 103

def reset
  i2c_write [RESET_REGISTER, RESET_COMMAND]
  sleep UPDATE_TIME
end

#state ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 92

def state
  @state ||= { temperature: nil, pressure: nil }
end

#update_state(reading) ⇒ Object 



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# File 'lib/denko/sensor/qmp6988.rb', line 214

def update_state(reading)
  @state_mutex.lock
  @state[:temperature] = reading[:temperature]
  @state[:pressure]    = reading[:pressure]
  @state_mutex.unlock
  @state
end