Skip to content

lsm9ds1: avoid unnecessary heap allocations #800

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: dev
Choose a base branch
from
Open

lsm9ds1: avoid unnecessary heap allocations #800

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
63 changes: 35 additions & 28 deletions lsm9ds1/lsm9ds1.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,6 @@ import (
"errors"

"tinygo.org/x/drivers"
"tinygo.org/x/drivers/internal/legacy"
)

type AccelRange uint8
Expand All @@ -28,7 +27,7 @@ type Device struct {
accelMultiplier int32
gyroMultiplier int32
magMultiplier int32
buf [6]uint8
buf [7]uint8 // up to 6 bytes for read + 1 byte for the register address
}

// Configuration for LSM9DS1 device.
Expand Down Expand Up @@ -61,19 +60,23 @@ func New(bus drivers.I2C) *Device {
// Case of boolean false and error nil means I2C is up,
// but "who am I" responses have unexpected values.
func (d *Device) Connected() bool {
data1, data2 := d.buf[:1], d.buf[1:2]
legacy.ReadRegister(d.bus, d.AccelAddress, WHO_AM_I, data1)
legacy.ReadRegister(d.bus, d.MagAddress, WHO_AM_I_M, data2)
return data1[0] == 0x68 && data2[0] == 0x3D
data, err := d.readBytes(d.AccelAddress, WHO_AM_I, 1)
if err != nil || data[0] != 0x68 {
return false
}
data, err = d.readBytes(d.MagAddress, WHO_AM_I_M, 1)
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

not required, but this could be rewritten as d.readByte (single byte return)

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Also heads up: regmap package implements read/write logic related to heapless register mapped peripherals, like this one https://github.com/tinygo-org/drivers/blob/dev/internal/regmap/devices.go

May help out in future modernizations :)

if err != nil || data[0] != 0x3D {
return false
}
return true
}

// 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, y, z int32, err error) {
data := d.buf[:6]
err = legacy.ReadRegister(d.bus, uint8(d.AccelAddress), OUT_X_L_XL, data)
data, err := d.readBytes(d.AccelAddress, OUT_X_L_XL, 6)
if err != nil {
return
}
Expand All @@ -88,8 +91,7 @@ func (d *Device) ReadAcceleration() (x, y, z int32, err error) {
// rotation along one axis and while doing so integrate all values over time,
// you would get a value close to 360000000.
func (d *Device) ReadRotation() (x, y, z int32, err error) {
data := d.buf[:6]
err = legacy.ReadRegister(d.bus, uint8(d.AccelAddress), OUT_X_L_G, data)
data, err := d.readBytes(d.AccelAddress, OUT_X_L_G, 6)
if err != nil {
return
}
Expand All @@ -102,8 +104,7 @@ func (d *Device) ReadRotation() (x, y, z int32, err error) {
// ReadMagneticField reads the current magnetic field from the device and returns
// it in nT (nanotesla). 1 G (gauss) = 100_000 nT (nanotesla).
func (d *Device) ReadMagneticField() (x, y, z int32, err error) {
data := d.buf[:6]
err = legacy.ReadRegister(d.bus, uint8(d.MagAddress), OUT_X_L_M, data)
data, err := d.readBytes(d.MagAddress, OUT_X_L_M, 6)
if err != nil {
return
}
Expand All @@ -115,8 +116,7 @@ func (d *Device) ReadMagneticField() (x, y, z int32, err error) {

// ReadTemperature returns the temperature in Celsius milli degrees (°C/1000)
func (d *Device) ReadTemperature() (t int32, err error) {
data := d.buf[:2]
err = legacy.ReadRegister(d.bus, uint8(d.AccelAddress), OUT_TEMP_L, data)
data, err := d.readBytes(d.AccelAddress, OUT_TEMP_L, 2)
if err != nil {
return
}
Expand Down Expand Up @@ -167,20 +167,16 @@ func (d *Device) doConfigure(cfg Configuration) (err error) {
d.magMultiplier = 58
}

data := d.buf[:1]

// Configure accelerometer
// Sample rate & measurement range
data[0] = uint8(cfg.AccelSampleRate)<<5 | uint8(cfg.AccelRange)<<3
err = legacy.WriteRegister(d.bus, d.AccelAddress, CTRL_REG6_XL, data)
err = d.writeByte(d.AccelAddress, CTRL_REG6_XL, uint8(cfg.AccelSampleRate)<<5|uint8(cfg.AccelRange)<<3)
if err != nil {
return
}

// Configure gyroscope
// Sample rate & measurement range
data[0] = uint8(cfg.GyroSampleRate)<<5 | uint8(cfg.GyroRange)<<3
err = legacy.WriteRegister(d.bus, d.AccelAddress, CTRL_REG1_G, data)
err = d.writeByte(d.AccelAddress, CTRL_REG1_G, uint8(cfg.GyroSampleRate)<<5|uint8(cfg.GyroRange)<<3)
if err != nil {
return
}
Expand All @@ -190,33 +186,44 @@ func (d *Device) doConfigure(cfg Configuration) (err error) {
// Temperature compensation enabled
// High-performance mode XY axis
// Sample rate
data[0] = 0b10000000 | 0b01000000 | uint8(cfg.MagSampleRate)<<2
err = legacy.WriteRegister(d.bus, d.MagAddress, CTRL_REG1_M, data)
err = d.writeByte(d.MagAddress, CTRL_REG1_M, 0b10000000|0b01000000|uint8(cfg.MagSampleRate)<<2)
if err != nil {
return
}

// Measurement range
data[0] = uint8(cfg.MagRange) << 5
err = legacy.WriteRegister(d.bus, d.MagAddress, CTRL_REG2_M, data)
err = d.writeByte(d.MagAddress, CTRL_REG2_M, uint8(cfg.MagRange)<<5)
if err != nil {
return
}

// Continuous-conversion mode
// https://electronics.stackexchange.com/questions/237397/continuous-conversion-vs-single-conversion-mode
data[0] = 0b00000000
err = legacy.WriteRegister(d.bus, d.MagAddress, CTRL_REG3_M, data)
err = d.writeByte(d.MagAddress, CTRL_REG3_M, 0b00000000)
if err != nil {
return
}

// High-performance mode Z axis
data[0] = 0b00001000
err = legacy.WriteRegister(d.bus, d.MagAddress, CTRL_REG4_M, data)
err = d.writeByte(d.MagAddress, CTRL_REG4_M, 0b00001000)
if err != nil {
return
}

return nil
}

func (d *Device) readBytes(addr, reg, size uint8) ([]byte, error) {
d.buf[0] = reg
err := d.bus.Tx(uint16(addr), d.buf[0:1], d.buf[1:size+1])
if err != nil {
return nil, err
}
return d.buf[1 : size+1], nil
}

func (d *Device) writeByte(addr, reg, value uint8) error {
d.buf[0] = reg
d.buf[1] = value
return d.bus.Tx(uint16(addr), d.buf[0:2], nil)
}