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MPL3115A2.py
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#!/usr/local/bin/python3
#
# MPL3115A2 Driver for Raspberry Pi
#
# This code is heavily copied from the Adafruit CircuitPython code (https://github.com/adafruit/Adafruit_CircuitPython_MPL3115A2)
# and adapted for use with the smbus library. This was mostly done as an exercise for me, since re-typing code is a good way to learn it.
from smbus2 import SMBus
from NOAA import NOAA
from threading import Timer
import logging
import time
#pylint: disable=bad-whitespace
# Internal constants:
_MPL3115A2_ADDRESS = 0x60
_MPL3115A2_REGISTER_STATUS = 0x00
_MPL3115A2_REGISTER_PRESSURE_MSB = 0x01
_MPL3115A2_REGISTER_PRESSURE_CSB = 0x02
_MPL3115A2_REGISTER_PRESSURE_LSB = 0x03
_MPL3115A2_REGISTER_TEMP_MSB = 0x04
_MPL3115A2_REGISTER_TEMP_LSB = 0x05
_MPL3115A2_REGISTER_DR_STATUS = 0x06
_MPL3115A2_OUT_P_DELTA_MSB = 0x07
_MPL3115A2_OUT_P_DELTA_CSB = 0x08
_MPL3115A2_OUT_P_DELTA_LSB = 0x09
_MPL3115A2_OUT_T_DELTA_MSB = 0x0A
_MPL3115A2_OUT_T_DELTA_LSB = 0x0B
_MPL3115A2_WHOAMI = 0x0C
_MPL3115A2_BAR_IN_MSB = 0x14
_MPL3115A2_BAR_IN_LSB = 0x15
_MPL3115A2_REGISTER_STATUS_TDR = 0x02
_MPL3115A2_REGISTER_STATUS_PDR = 0x04
_MPL3115A2_REGISTER_STATUS_PTDR = 0x08
_MPL3115A2_PT_DATA_CFG = 0x13
_MPL3115A2_PT_DATA_CFG_TDEFE = 0x01
_MPL3115A2_PT_DATA_CFG_PDEFE = 0x02
_MPL3115A2_PT_DATA_CFG_DREM = 0x04
_MPL3115A2_CTRL_REG1 = 0x26
_MPL3115A2_CTRL_REG2 = 0x27
_MPL3115A2_CTRL_REG3 = 0x28
_MPL3115A2_CTRL_REG4 = 0x29
_MPL3115A2_CTRL_REG5 = 0x2A
_MPL3115A2_CTRL_REG1_SBYB = 0x01
_MPL3115A2_CTRL_REG1_OST = 0x02
_MPL3115A2_CTRL_REG1_RST = 0x04
_MPL3115A2_CTRL_REG1_RAW = 0x40
_MPL3115A2_CTRL_REG1_ALT = 0x80
_MPL3115A2_CTRL_REG1_BAR = 0x00
_MPL3115A2_CTRL_REG1_OS1 = 0x00
_MPL3115A2_CTRL_REG1_OS2 = 0x08
_MPL3115A2_CTRL_REG1_OS4 = 0x10
_MPL3115A2_CTRL_REG1_OS8 = 0x18
_MPL3115A2_CTRL_REG1_OS16 = 0x20
_MPL3115A2_CTRL_REG1_OS32 = 0x28
_MPL3115A2_CTRL_REG1_OS64 = 0x30
_MPL3115A2_CTRL_REG1_OS128 = 0x38
_MPL3115A2_REGISTER_STARTCONVERSION = 0x12
#pylint: enable=bad-whitespace
class MPL3115A2:
def __init__(self, i2cBusID, address=_MPL3115A2_ADDRESS, fetchPressure=True):
# If fetchPressure is True then this library will send requests to geolocate the current IP and fetch weather data from the nearest station using the NOAA API.
logging.debug("🌟 Hello, World!")
# Bring up SMBus
self.bus = SMBus(i2cBusID)
if self.bus is None:
raise Exception("Couldn't init I2C bus with identifier %x" % i2cBusID)
self.address = address
# Check that we can speak to the chip and that we're dealing with the right chip
whoami = self.bus.read_byte_data(self.address, _MPL3115A2_WHOAMI)
if whoami != 0xC4:
raise Exception("I2C device found at address %0x but it is not a MPL3115A2 chip (whoami returned %0x)" % (self.address, whoami))
logging.debug("📟 Connected to MPL3115A2 chip")
# Kick off a reset so that we know the configuration of the device
# I'm not sure this is the best idea, but it's the simplest, and it's what the Adafruit library does so I'm copying it for now
logging.debug("⚡️ Initiating a reset...")
# Ignore write errors since the chip might reset in the middle of our message
try:
self.bus.write_byte_data(self.address, _MPL3115A2_CTRL_REG1, _MPL3115A2_CTRL_REG1_RST)
except OSError:
pass
self._pollForReg1(_MPL3115A2_CTRL_REG1_RST)
logging.debug("💫 Chip has been reset")
logging.debug("😶 Configuring chip...")
self._ctrlReg1 = (_MPL3115A2_CTRL_REG1_ALT | _MPL3115A2_CTRL_REG1_OS128)
self._writeReg1()
if fetchPressure is True:
seaLevelPressure = 0
self.noaa = NOAA()
self._updatePressure()
self.bus.write_byte_data(self.address, _MPL3115A2_PT_DATA_CFG, (_MPL3115A2_PT_DATA_CFG_TDEFE | _MPL3115A2_PT_DATA_CFG_PDEFE | _MPL3115A2_PT_DATA_CFG_DREM))
logging.debug("✅ Chip activated!")
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
logging.info("🌅 Shutting down. Goodbye!")
self.bus.close()
def _writeReg1(self, requestData=False):
if requestData is True:
self._ctrlReg1 |= _MPL3115A2_CTRL_REG1_OST
else:
self._ctrlReg1 &= ~_MPL3115A2_CTRL_REG1_OST
logging.debug("⚙️ Setting control register to %x" % self._ctrlReg1)
self.bus.write_byte_data(self.address, _MPL3115A2_CTRL_REG1, self._ctrlReg1)
def _pollForReg1(self, mask):
while self.bus.read_byte_data(self.address, _MPL3115A2_CTRL_REG1) & mask > 0:
time.sleep(0.01)
def _pollForStatus(self, mask):
while self.bus.read_byte_data(self.address, _MPL3115A2_REGISTER_STATUS) & mask == 0:
time.sleep(0.01)
def _updatePressure(self):
try:
logging.debug("🌦 Fetching pressure data from NOAA...")
pressure = self.noaa.getCurrentSeaLevelPressure()
logging.debug("⛈🌡 Pressure fetched from NOAA is %dPa" % pressure)
self.seaLevelPressure = pressure
except Exception as e:
logging.info("🚨 Error fetching pressure data from NOAA: {}".format(e))
# ----
# Temperature
@property
def temperature(self):
self._pollForStatus(_MPL3115A2_REGISTER_STATUS_TDR)
tempBytes = self.bus.read_i2c_block_data(self.address, _MPL3115A2_REGISTER_TEMP_MSB, 2)
return (tempBytes[0]) + ((tempBytes[1]>>4 & 0x0F)/16.0)
# ----
# ----
# Altitude
@property
def altitude(self):
# Wait for any previous measurements to finish
self._pollForReg1(_MPL3115A2_CTRL_REG1_OST)
if (self._ctrlReg1 & _MPL3115A2_CTRL_REG1_ALT) != _MPL3115A2_CTRL_REG1_ALT:
self._ctrlReg1 |= _MPL3115A2_CTRL_REG1_ALT
self._writeReg1()
# Request a sensor read
self._writeReg1(requestData=True)
# Wait for PDR to be set
self._pollForStatus(_MPL3115A2_REGISTER_STATUS_PDR)
altitudeBytes = self.bus.read_i2c_block_data(self.address, _MPL3115A2_REGISTER_PRESSURE_MSB, 3)
logging.debug("🗻 Altitude data read from chip is %s" % (",".join([hex(i) for i in altitudeBytes])))
# The reading is a 20 bit value. The first two bytes are the meters (in 2's complement) and the third byte is the fractions of a meter, stored in the top four bits (not 2's complement)
return (altitudeBytes[0]<<8 | altitudeBytes[1]) + ((altitudeBytes[2]>>4 & 0x0F)/16.0)
@property
def seaLevelPressure(self):
pressureBytes = self.bus.read_i2c_block_data(self.address, _MPL3115A2_BAR_IN_MSB, 2)
return ((pressureBytes[0] << 8) | (pressureBytes[1])) << 1
@seaLevelPressure.setter
def seaLevelPressure(self, pressure):
pressure //= 2
pressureLSB = pressure & 0xFF
pressureMSB = (pressure >> 8) & 0xFF
logging.debug("🌡 Writing pressure data of %dPa (%d, %0x|%0x)" % (pressure >> 1, pressure, pressureMSB, pressureLSB))
self.bus.write_i2c_block_data(self.address, _MPL3115A2_BAR_IN_MSB, [pressureMSB, pressureLSB])
# ----
# ----
# Pressure
@property
def pressure(self):
# Wait for any previous measurements to finish
self._pollForReg1(_MPL3115A2_CTRL_REG1_OST)
if (self._ctrlReg1 & _MPL3115A2_CTRL_REG1_ALT) == _MPL3115A2_CTRL_REG1_ALT:
self._ctrlReg1 &= ~_MPL3115A2_CTRL_REG1_ALT
self._writeReg1()
# Request a sensor read
self._writeReg1(requestData=True)
# Wait for PDR to be set
self._pollForStatus(_MPL3115A2_REGISTER_STATUS_PDR)
pressureBytes = self.bus.read_i2c_block_data(self.address, _MPL3115A2_REGISTER_PRESSURE_MSB, 3)
logging.debug("🌬 Pressure data read from chip is %s" % (",".join([hex(i) for i in pressureBytes])))
# The reading is a 20 bit value. The first two bytes are the meters (in 2's complement) and the third byte is the fractions of a meter, stored in the top four bits (not 2's complement)
return (pressureBytes[0]<<10 | pressureBytes[1]<<2 | ((pressureBytes[2]&0xC0 >> 6) & 0x03a)) + ((pressureBytes[2]>>4 & 0x03)/4.0)