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mpl3115a2.go
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//--------------------------------------------------------------------------------------------------
//
// Copyright (c) 2018 Denis Dyakov
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
// associated documentation files (the "Software"), to deal in the Software without restriction,
// including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or substantial
// portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
// BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//--------------------------------------------------------------------------------------------------
package mpl3115a2
import (
"encoding/binary"
"errors"
"time"
i2c "github.com/d2r2/go-i2c"
)
// Register map
const (
// Alias for DR_STATUS or F_STATUS
STATUS = 0x00
// 20-bit realtime pressure sample
OUT_PRES_MSB_CSB_LSB = 0x01
OUT_PRES_BYTES = 3
// 12-bit realtime temperature sample
OUT_TEMP_MSB_LSB = 0x04
OUT_TEMP_BYTES = 2
// Data ready status information
DR_STATUS = 0x06
// 20-bit pressure change data
OUT_PRES_DELTA_MSB_CSB_LSB = 0x07
OUT_PRES_DELTA_BYTES = 3
// 12-bit temperature change data
OUT_TEMP_DELTA_MSB_LSB = 0x0A
OUT_TEMP_DELTA_BYTES = 2
// Fixed device ID number
WHO_AM_I = 0x0C
// FIFO status: no FIFO event detected
F_STATUS = 0x0D
// FIFO 8-bit data access
F_DATA = 0x0E
// FIFO setup
F_SETUP = 0x0F
// Time since FIFO overflow
TIME_DLY = 0x10
// Current system mode
SYSMOD = 0x11
// Interrupt status
INT_SOURCE = 0x12
// Data event flag configuration
PT_DATA_CFG = 0x13
// Barometric input for altitude calculation
BAR_IN_MSB_LSB = 0x14
BAR_IN_BYTES = 2
// Pressure/altitude target
PRES_TGT_MSB_LSB = 0x16
PRES_TGT_BYTES = 2
// Temperature target value
T_TGT = 0x18
// Pressure/altitude window
PRES_WND_MSB_LSB = 0x19
PRES_WND_BYTES = 2
// Temperature window
TEMP_WND = 0x1B
// Minimum pressure/altitude
PRES_MIN_MSB_CSB_LSB = 0x1C
PRES_MIN_BYTES = 3
// Minimum temperature
TEMP_MIN_MSB_LSB = 0x1E
TEMP_MIN_BYTES = 2
// Maximum pressure/altitude
PRES_MAX_MSB_CSB_LSB = 0x21
PRES_MAX_BYTES = 3
// Maximum temperature
TEMP_MAX_MSB_LSB = 0x24
TEMP_MAX_BYTES = 2
// Control register: Modes, oversampling
CTRL_REG1 = 0x26
// Control register: Acquisition time step
CTRL_REG2 = 0x27
// Control register: Interrupt pin configuration
CTRL_REG3 = 0x28
// Control register: Interrupt enables
CTRL_REG4 = 0x29
// Control register: Interrupt output pin assignment
CTRL_REG5 = 0x2A
// Pressure data offset
OFF_PRES = 0x2B
// Temperature data offset
OFF_TEMP = 0x2C
// Altitude data offset
OFF_H = 0x2D
)
// Flag can keep any sensor register specific bit flags.
type Flag byte
const (
// DR_STATUS flag: Pressure/altitude or temperature data ready.
PRES_TEMP_DATA_READY Flag = 0x8
// DR_STATUS flag: Pressure/altitude new data available.
PRES_DATA_READY Flag = 0x4
// DR_STATUS flag: Temperature new data available.
TEMP_DATA_READY Flag = 0x2
)
// PressureType signify which type of
// pressure measurement in use.
type PressureType int
const (
// Measure pressure in Pa
Barometer PressureType = iota + 1
// Measure altitude in m
Altimeter
)
// RawPressure keeps raw pressure data received from sensor.
type RawPressure struct {
PRES_MSB byte
PRES_CSB byte
PRES_LSB byte
}
// ConvertToSignedQ16Dot4 convert raw data to signed Q16.4,
// where integer and fraction parts returned in separate fields.
// Used for altimeter mode.
func (v *RawPressure) ConvertToSignedQ16Dot4() (int16, uint8) {
presFrac := (v.PRES_LSB & 0xF0) >> 4
presInt := int16((uint16(v.PRES_MSB) << 8) | uint16(v.PRES_CSB))
return presInt, presFrac
}
// ConvertToUnsignedQ18Dot2 convert raw data to unsigned Q18.2,
// where integer and fraction parts returned in separate fields.
// Used for barometer mode.
func (v *RawPressure) ConvertToUnsignedQ18Dot2() (uint32, uint8) {
presFrac := (v.PRES_LSB & 0xF0) >> 4
presInt := (uint32(v.PRES_MSB) << 10) | (uint32(v.PRES_CSB) << 2) | uint32(presFrac>>2)
presFrac &= 0x3
return presInt, presFrac
}
// RawTemperature keeps raw temperature data received from sensor.
type RawTemperature struct {
TEMP_MSB byte
TEMP_LSB byte
}
// ConvertToSignedQ8Dot4 convert raw data to signed Q8.4,
// where integer and fraction parts returned in separate fields.
func (v *RawTemperature) ConvertToSignedQ8Dot4() (int8, uint8) {
tempFrac := (v.TEMP_LSB & 0xF0) >> 4
tempInt := int8(v.TEMP_MSB)
return tempInt, tempFrac
}
// MPL3115A2 keeps sensor itself.
type MPL3115A2 struct {
}
// NewMPL3115A2 return new sensor instance.
func NewMPL3115A2() *MPL3115A2 {
v := &MPL3115A2{}
return v
}
// Oversample ratio should in range [0..7], where final value equal to 2^osr.
func (v *MPL3115A2) encodeCtrlOverSampleRatio(oversample int) (byte, error) {
if oversample < 0 || oversample > 7 {
return 0, errors.New("oversample ratio should be in range [0..7]")
}
b := byte(oversample) << 3
return b, nil
}
// Define measure for altimeter/barometer mode.
// Altimeter mode return "pressure" value in meters,
// barometer mode in Pascals.
func (v *MPL3115A2) encodeCtrlAltimeterMode(altimeterMode bool) (byte, error) {
if altimeterMode {
return 0x80, nil
}
return 0, nil
}
// Activate/deactivate reset bit.
func (v *MPL3115A2) encodeCtrlResetBit(activateReset bool) (byte, error) {
if activateReset {
return 0x4, nil
}
return 0, nil
}
// Put sensor in ACTIVE/STANDBY mode.
func (v *MPL3115A2) encodeCtrlActiveStatus(activateSensor bool) (byte, error) {
if activateSensor {
return 0x1, nil
}
return 0, nil
}
// Read STATUS register.
func (v *MPL3115A2) readStatusReg(i2c *i2c.I2C) (Flag, error) {
status, err := i2c.ReadRegU8(STATUS)
if err != nil {
return 0, err
}
return Flag(status), nil
}
// Write CTRL_REG1 register.
func (v *MPL3115A2) writeCtrlReg1(i2c *i2c.I2C, value byte) error {
err := i2c.WriteRegU8(CTRL_REG1, value)
if err != nil {
return err
}
return nil
}
// Write PT_DATE_CFG register to define events.
func (v *MPL3115A2) writeEventMode(i2c *i2c.I2C,
temperatureEvent, preasureEvent bool) error {
var flags byte
if temperatureEvent {
flags |= 0x1
}
if preasureEvent {
flags |= 0x2
}
if temperatureEvent || preasureEvent {
flags |= 0x4
}
err := i2c.WriteRegU8(PT_DATA_CFG, flags)
if err != nil {
return err
}
return nil
}
// MeasureAltitude measure altitude in meters with specific
// precision defined by oversample ratio.
func (v *MPL3115A2) MeasureAltitude(i2c *i2c.I2C, oversampleRatio int) (float32, float32, error) {
up, ut, err := v.measureRaw(i2c, oversampleRatio, Altimeter)
if err != nil {
return 0, 0, err
}
presInt, presFrac := up.ConvertToSignedQ16Dot4()
tempInt, tempFrac := ut.ConvertToSignedQ8Dot4()
alt := float32(presInt) + float32(presFrac)/(1<<4)
t := float32(tempInt) + float32(tempFrac)/(1<<4)
return alt, t, nil
}
// MeasurePressure measure pressure in Pa with specific
// precision defined by oversample ratio.
func (v *MPL3115A2) MeasurePressure(i2c *i2c.I2C, oversampleRation int) (float32, float32, error) {
up, ut, err := v.measureRaw(i2c, oversampleRation, Barometer)
if err != nil {
return 0, 0, err
}
presInt, presFrac := up.ConvertToUnsignedQ18Dot2()
tempInt, tempFrac := ut.ConvertToSignedQ8Dot4()
pres := float32(presInt) + float32(presFrac)/(1<<2)
t := float32(tempInt) + float32(tempFrac)/(1<<4)
return pres, t, nil
}
// Initialize sensor and made raw measurement
// to read uncompensated pressure and temperature.
func (v *MPL3115A2) measureRaw(i2c *i2c.I2C, overampleRatio int,
pressureType PressureType) (*RawPressure, *RawTemperature, error) {
lg.Debug("Measurement pressure and temperature...")
// enable Altimeter mode
var barometerType bool
if pressureType == Altimeter {
barometerType = true
}
flags, err := v.encodeCtrlAltimeterMode(barometerType)
if err != nil {
return nil, nil, err
}
// define Oversample Ratio to 2^oversampleRatio
b, err := v.encodeCtrlOverSampleRatio(overampleRatio)
if err != nil {
return nil, nil, err
}
flags |= b
// activate Altimeter mode and set Oversample Ratio
err = v.writeCtrlReg1(i2c, flags)
if err != nil {
return nil, nil, err
}
// enable events for temperature and pressure
err = v.writeEventMode(i2c, true, true)
if err != nil {
return nil, nil, err
}
// get activate sensor bit
b, err = v.encodeCtrlActiveStatus(true)
if err != nil {
return nil, nil, err
}
flags |= b
// activate sensor
err = v.writeCtrlReg1(i2c, flags)
if err != nil {
return nil, nil, err
}
// read status until measurement is done
for {
var n time.Duration = 1
// n = 1 << overampleRatio
time.Sleep(time.Millisecond * 2 * n)
status, err := v.readStatusReg(i2c)
if err != nil {
return nil, nil, err
}
if status&PRES_TEMP_DATA_READY != 0 {
break
}
}
up, ut, err := v.readRawPressureTemperature(i2c)
if err != nil {
return nil, nil, err
}
return up, ut, nil
}
// Read uncompensated temperature and pressure sensor measurement.
func (v *MPL3115A2) readRawPressureTemperature(i2c *i2c.I2C) (*RawPressure, *RawTemperature, error) {
_, err := i2c.WriteBytes([]byte{STATUS})
if err != nil {
return nil, nil, err
}
var data struct {
STATUS byte
RawPressure
RawTemperature
}
err = readDataToStruct(i2c, 1+OUT_PRES_BYTES+OUT_TEMP_BYTES, binary.LittleEndian, &data)
if err != nil {
return nil, nil, err
}
// lg.Debugf("Data = %+v", data)
return &data.RawPressure, &data.RawTemperature, nil
}
// ModifySeaLevelPressure call allow to change default sea level value 101326 Pa to custom one.
func (v *MPL3115A2) ModifySeaLevelPressure(i2c *i2c.I2C, pressureAtSeeLevel uint32) error {
// divide by 2
pressureAtSeeLevel = pressureAtSeeLevel / 2
b := []byte{BAR_IN_MSB_LSB, byte(pressureAtSeeLevel >> 8), byte(pressureAtSeeLevel & 0xFF)}
_, err := i2c.WriteBytes(b)
if err != nil {
return err
}
return nil
}
// GetDefaultSeaLevelPressure return average barometric pressure
// on the sea level defined as 101325 Pa.
func (v *MPL3115A2) GetDefaultSeaLevelPressure() uint32 {
return 101326
}
// Reset reboot sensor and initialize some sensor registers.
func (v *MPL3115A2) Reset(i2c *i2c.I2C) error {
lg.Debug("Reset sensor...")
flags, err := v.encodeCtrlResetBit(true)
if err != nil {
return err
}
// activate reset bit
err = v.writeCtrlReg1(i2c, flags)
// ignore error, since sensor terminates i2c-connection
return nil
}
// CompensateAltitude shift altitude from -128 to +127 meters.
// Default value is 0. Can be used for sensor calibration.
func (v *MPL3115A2) CompensateAltitude(i2c *i2c.I2C, shiftM int8) error {
b := []byte{OFF_H, byte(shiftM)}
_, err := i2c.WriteBytes(b)
if err != nil {
return err
}
return nil
}
// CompensatePressure shift pressure from -512 to +508 Pascal.
// Default value is 0. Can be user for sensor calibration.
func (v *MPL3115A2) CompensatePressure(i2c *i2c.I2C, shiftPa int16) error {
if shiftPa > 508 || shiftPa < -512 {
return errors.New("pressure compensation exceed range [-512..+508]")
}
// divide by 4
shiftPa = shiftPa / 4
b := []byte{OFF_PRES, byte(shiftPa)}
_, err := i2c.WriteBytes(b)
if err != nil {
return err
}
return nil
}
// CompensateTemperature shift temperature from -8 to +7.9375 *C.
// Default value is 0. Can be used for sensor calibration.
func (v *MPL3115A2) CompensateTemperature(i2c *i2c.I2C, shiftTemp float32) error {
if shiftTemp > 7.9375 || shiftTemp < -8 {
return errors.New("temperature compensation exceed range [-8..+7.9375]")
}
// multiply by 16
shiftTemp = shiftTemp * 16
b := []byte{OFF_PRES, byte(shiftTemp)}
_, err := i2c.WriteBytes(b)
if err != nil {
return err
}
return nil
}