/
lsm303agr.go
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/
lsm303agr.go
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// Package lsm303agr implements a driver for the LSM303AGR,
// a 3 axis accelerometer/magnetic sensor which is included on BBC micro:bits v1.5.
//
// Datasheet: https://www.st.com/resource/en/datasheet/lsm303agr.pdf
//
package lsm303agr // import "tinygo.org/x/drivers/lsm303agr"
import (
"math"
"tinygo.org/x/drivers"
)
// Device wraps an I2C connection to a LSM303AGR device.
type Device struct {
bus drivers.I2C
AccelAddress uint8
MagAddress uint8
AccelPowerMode uint8
AccelRange uint8
AccelDataRate uint8
MagPowerMode uint8
MagSystemMode uint8
MagDataRate uint8
}
// Configuration for LSM303AGR device.
type Configuration struct {
AccelPowerMode uint8
AccelRange uint8
AccelDataRate uint8
MagPowerMode uint8
MagSystemMode uint8
MagDataRate uint8
}
// New creates a new LSM303AGR connection. The I2C bus must already be
// configured.
//
// This function only creates the Device object, it does not touch the device.
func New(bus drivers.I2C) Device {
return Device{bus: bus, AccelAddress: ACCEL_ADDRESS, MagAddress: MAG_ADDRESS}
}
// Connected returns whether both sensor on LSM303AGR has been found.
// It does two "who am I" requests and checks the responses.
func (d *Device) Connected() bool {
data1, data2 := []byte{0}, []byte{0}
d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_WHO_AM_I, data1)
d.bus.ReadRegister(uint8(d.MagAddress), MAG_WHO_AM_I, data2)
return data1[0] == 0x33 && data2[0] == 0x40
}
// Configure sets up the LSM303AGR device for communication.
func (d *Device) Configure(cfg Configuration) {
if cfg.AccelDataRate != 0 {
d.AccelDataRate = cfg.AccelDataRate
} else {
d.AccelDataRate = ACCEL_DATARATE_100HZ
}
if cfg.AccelPowerMode != 0 {
d.AccelPowerMode = cfg.AccelPowerMode
} else {
d.AccelPowerMode = ACCEL_POWER_NORMAL
}
if cfg.AccelRange != 0 {
d.AccelRange = cfg.AccelRange
} else {
d.AccelRange = ACCEL_RANGE_2G
}
if cfg.MagPowerMode != 0 {
d.MagPowerMode = cfg.MagPowerMode
} else {
d.MagPowerMode = MAG_POWER_NORMAL
}
if cfg.MagDataRate != 0 {
d.MagDataRate = cfg.MagDataRate
} else {
d.MagDataRate = MAG_DATARATE_10HZ
}
if cfg.MagSystemMode != 0 {
d.MagSystemMode = cfg.MagSystemMode
} else {
d.MagSystemMode = MAG_SYSTEM_CONTINUOUS
}
cmd := []byte{0}
cmd[0] = byte(d.AccelDataRate<<4 | d.AccelPowerMode | 0x07)
d.bus.WriteRegister(uint8(d.AccelAddress), ACCEL_CTRL_REG1_A, cmd)
cmd[0] = byte(0x80 | d.AccelRange<<4)
d.bus.WriteRegister(uint8(d.AccelAddress), ACCEL_CTRL_REG4_A, cmd)
cmd[0] = byte(0xC0)
d.bus.WriteRegister(uint8(d.AccelAddress), TEMP_CFG_REG_A, cmd)
// Temperature compensation is on for magnetic sensor
cmd[0] = byte(0x80 | d.MagPowerMode<<4 | d.MagDataRate<<2 | d.MagSystemMode)
d.bus.WriteRegister(uint8(d.MagAddress), MAG_MR_REG_M, cmd)
}
// ReadAcceleration reads the current acceleration from the device and returns
// it in µg (micro-gravity). When one of the axes is pointing straight to Earth
// and the sensor is not moving the returned value will be around 1000000 or
// -1000000.
func (d *Device) ReadAcceleration() (x int32, y int32, z int32) {
data1, data2, data3, data4, data5, data6 := []byte{0}, []byte{0}, []byte{0}, []byte{0}, []byte{0}, []byte{0}
d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_X_H_A, data1)
d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_X_L_A, data2)
d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_Y_H_A, data3)
d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_Y_L_A, data4)
d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_Z_H_A, data5)
d.bus.ReadRegister(uint8(d.AccelAddress), ACCEL_OUT_Z_L_A, data6)
rangeFactor := int16(0)
switch d.AccelRange {
case ACCEL_RANGE_2G:
rangeFactor = 1
case ACCEL_RANGE_4G:
rangeFactor = 2
case ACCEL_RANGE_8G:
rangeFactor = 4
case ACCEL_RANGE_16G:
rangeFactor = 12 // the readings in 16G are a bit lower
}
x = int32(int32(int16((uint16(data1[0])<<8|uint16(data2[0])))>>4*rangeFactor) * 1000000 / 1024)
y = int32(int32(int16((uint16(data3[0])<<8|uint16(data4[0])))>>4*rangeFactor) * 1000000 / 1024)
z = int32(int32(int16((uint16(data5[0])<<8|uint16(data6[0])))>>4*rangeFactor) * 1000000 / 1024)
return
}
// ReadPitchRoll reads the current pitch and roll angles from the device and
// returns it in micro-degrees. When the z axis is pointing straight to Earth
// the returned values of pitch and roll would be zero.
func (d *Device) ReadPitchRoll() (pitch int32, roll int32) {
x, y, z := d.ReadAcceleration()
xf, yf, zf := float64(x), float64(y), float64(z)
pitch = int32((math.Round(math.Atan2(yf, math.Sqrt(math.Pow(xf, 2)+math.Pow(zf, 2)))*(180/math.Pi)*100) / 100) * 1000000)
roll = int32((math.Round(math.Atan2(xf, math.Sqrt(math.Pow(yf, 2)+math.Pow(zf, 2)))*(180/math.Pi)*100) / 100) * 1000000)
return
}
// ReadMagneticField reads the current magnetic field from the device and returns
// it in mG (milligauss). 1 mG = 0.1 µT (microtesla).
func (d *Device) ReadMagneticField() (x int32, y int32, z int32) {
if d.MagSystemMode == MAG_SYSTEM_SINGLE {
cmd := []byte{0}
cmd[0] = byte(0x80 | d.MagPowerMode<<4 | d.MagDataRate<<2 | d.MagSystemMode)
d.bus.WriteRegister(uint8(d.MagAddress), MAG_MR_REG_M, cmd)
}
data1, data2, data3, data4, data5, data6 := []byte{0}, []byte{0}, []byte{0}, []byte{0}, []byte{0}, []byte{0}
d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_X_H_M, data1)
d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_X_L_M, data2)
d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_Y_H_M, data3)
d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_Y_L_M, data4)
d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_Z_H_M, data5)
d.bus.ReadRegister(uint8(d.MagAddress), MAG_OUT_Z_L_M, data6)
x = int32(int16((uint16(data1[0])<<8 | uint16(data2[0]))))
y = int32(int16((uint16(data3[0])<<8 | uint16(data4[0]))))
z = int32(int16((uint16(data5[0])<<8 | uint16(data6[0]))))
return
}
// ReadCompass reads the current compass heading from the device and returns
// it in micro-degrees. When the z axis is pointing straight to Earth and
// the y axis is pointing to North, the heading would be zero.
//
// However, the heading may be off due to electronic compasses would be effected
// by strong magnetic fields and require constant calibration.
func (d *Device) ReadCompass() (h int32) {
x, y, _ := d.ReadMagneticField()
xf, yf := float64(x), float64(y)
h = int32(float32((180/math.Pi)*math.Atan2(yf, xf)) * 1000000)
return
}
// ReadTemperature returns the temperature in Celsius milli degrees (°C/1000)
func (d *Device) ReadTemperature() (c int32, e error) {
data1, data2 := []byte{0}, []byte{0}
d.bus.ReadRegister(uint8(d.AccelAddress), OUT_TEMP_H_A, data1)
d.bus.ReadRegister(uint8(d.AccelAddress), OUT_TEMP_L_A, data2)
t := int16((uint16(data1[0])<<8 | uint16(data2[0]))) >> 4 // temperature offsef from 25 °C
c = int32((float32(25) + float32(t)/8) * 1000)
e = nil
return
}