Add support for ams AS560x on-axis magnetic rotary position sensors

Makefile

@@ -251,6 +251,8 @@ endif
 	@md5sum ./build/test.uf2
 	tinygo build -size short -o ./build/test.hex -target=nucleo-wl55jc ./examples/lora/lorawan/atcmd/
 	@md5sum ./build/test.hex
+	tinygo build -size short -o ./build/test.uf2 -target=pico ./examples/as560x/main.go
+	@md5sum ./build/test.uf2
 
 
 # rwildcard is a recursive version of $(wildcard) 

README.md

@@ -62,6 +62,7 @@ The following 90 devices are supported.
 | [AMG88xx 8x8 Thermal camera sensor](https://cdn-learn.adafruit.com/assets/assets/000/043/261/original/Grid-EYE_SPECIFICATIONS%28Reference%29.pdf)                                                   | I2C |
 | [APA102 RGB LED](https://cdn-shop.adafruit.com/product-files/2343/APA102C.pdf)                                                                                                                      | SPI |
 | [APDS9960 Digital proximity, ambient light, RGB and gesture sensor](https://cdn.sparkfun.com/assets/learn_tutorials/3/2/1/Avago-APDS-9960-datasheet.pdf)                                            | I2C |
+| [AS5600](https://ams.com/documents/20143/36005/AS5600_DS000365_5-00.pdf) / [AS5601](https://ams.com/documents/20143/36005/AS5601_DS000395_3-00.pdf) [on-axis magnetic rotary position sensors](https://ams.com/angle-position-on-axis) | I2C |
 | [AT24CX 2-wire serial EEPROM](https://www.openimpulse.com/blog/wp-content/uploads/wpsc/downloadables/24C32-Datasheet.pdf)                                                                           | I2C |
 | [AXP192 single Cell Li-Battery and Power System Management](https://github.com/m5stack/M5-Schematic/blob/master/Core/AXP192%20Datasheet_v1.1_en_draft_2211.pdf)                                     | I2C |
 | [BBC micro:bit LED matrix](https://github.com/bbcmicrobit/hardware/blob/master/SCH_BBC-Microbit_V1.3B.pdf)                                                                                          | GPIO |

as560x/as5600.go

@@ -0,0 +1,172 @@
+//	Product: https://ams.com/as5600
+//	Datasheet: https://ams.com/documents/20143/36005/AS5600_DS000365_5-00.pdf
+
+package as560x // import tinygo.org/x/drivers/ams560x
+
+import (
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+// AS5600 includes MPOS & MANG in addition to ZPOS to set a 'narrower angle range'
+// ZPOS enables setting the 'zero position' of the device to any RAW_ANGLE value.
+// MPOS ('max position') & MANG 'max angle' enable a 'partial range' on the AS5600.
+// The value in ANGLE is scaled & adjusted by the device according to ZPOS and MPOS/MANG.
+// The entire 12-bit range is 'compressed' into the RAW_ANGLE range of ZPOS->MPOS
+// (or ZPOS->ZPOS+MANG) thus enabling a higher resolution for a partial range.
+// if ZPOS > MPOS (or ZPOS + MANG > 4095) i.e. the incremental range 'crosses zero'
+// then the device will automatically compensate for the correct range.
+// For RAW_ANGLE values outside of the partial range, ANGLE will be 'capped' at either
+// 0 or 4095, depending on 'which end of the partial range is closer.'
+
+// AS5600Device represents an ams AS5600 device driver accessed over I2C
+type AS5600Device struct {
+	// promote BaseDevice
+	BaseDevice
+}
+
+// NewAS5600 creates a new AS5600Device given an I2C bus
+func NewAS5600(bus drivers.I2C) AS5600Device {
+	// Create base device
+	baseDev := newBaseDevice(bus)
+	// Add AS5600 specific registers
+	baseDev.registers[MPOS] = newI2CRegister(MPOS, 0, 0xfff, 2, reg_read|reg_write|reg_program)
+	baseDev.registers[MANG] = newI2CRegister(MANG, 0, 0xfff, 2, reg_read|reg_write|reg_program)
+	// Add AS5600 specific 'virtual registers'
+	conf, ok := baseDev.registers[CONF]
+	if ok {
+		baseDev.registers[PWMF] = newVirtualRegister(conf, 6, 0b11)
+		baseDev.registers[OUTS] = newVirtualRegister(conf, 4, 0b11)
+	}
+	// Return the device
+	return AS5600Device{baseDev}
+}
+
+// Configure sets up the AMS AS5600 sensor device with the given configuration.
+func (d *AS5600Device) Configure(cfg Config) error {
+	// Call the BaseDevice method to do the actual Configure
+	d.BaseDevice.Configure(cfg)
+	// For AS5600 devices we need to calculate the maxAngle on startup from ZPOS/MPOS/MANG
+	// These could have been permanently BURN'ed (by writing BURN register with BURN_ANGLE/BURN_SETTING)
+	// or may have already been written in previous runs without a power cycle since.
+	mpos, err := d.ReadRegister(MPOS)
+	if nil != err {
+		return err
+	}
+	mang, err := d.ReadRegister(MANG)
+	if nil != err {
+		return err
+	}
+	// Read ZPOS for side effect of caching only so that next calculateEffectiveMaxAngle() can't fail
+	if _, err = d.ReadRegister(ZPOS); nil != err {
+		return err
+	}
+	if mpos != 0 {
+		// If MPOS is set, use MPOS regardless of MANG
+		err = d.calculateEffectiveMaxAngle(MPOS, mpos)
+	} else if mang != 0 {
+		// If MANG is set and MPOS == 0, use MANG
+		err = d.calculateEffectiveMaxAngle(MANG, mang)
+	} else {
+		// if neither is set, we have no narrow range
+		d.maxAngle = NATIVE_ANGLE_RANGE
+	}
+	return err
+}
+
+// calculateEffectiveMaxAngle calculates d.maxAngle after one of ZPOS/MPOS/MANG have been written
+func (d *AS5600Device) calculateEffectiveMaxAngle(register uint8, value uint16) error {
+
+	var zpos, mpos uint16 = 0, 0
+	var err error = nil
+
+	switch register {
+	case MANG:
+		d.maxAngle = value // The easy case
+		return nil
+	case ZPOS:
+		zpos = value
+		mpos, err = d.ReadRegister(MPOS)
+	case MPOS:
+		mpos = value
+		zpos, err = d.ReadRegister(ZPOS)
+	default:
+		panic("calculateEffectiveMaxAngle() can only work from ZPOS, MPOS or MANG")
+	}
+
+	if nil != err {
+		return err
+	}
+	// MANG is effectively MPOS-ZPOS
+	mang := int(mpos) - int(zpos)
+	// correct for mpos < zpos
+	if mang < 0 {
+		mang += NATIVE_ANGLE_RANGE
+	}
+	d.maxAngle = uint16(mang)
+	return nil
+}
+
+// WriteRegister writes the given value for the given register to the AS560x device via I2C
+func (d *AS5600Device) WriteRegister(address uint8, value uint16) error {
+	// Call the BaseDevice method to do the actual write
+	if err := d.BaseDevice.WriteRegister(address, value); err != nil {
+		return err
+	}
+	// When either ZPOS/MANG/MPOS are set we need to recalculate maxAngle
+	// We also may need to invalidate some cached values for the other two registers
+	recalc := false
+	switch address {
+	case ZPOS:
+		// Setting a new ZPOS invalidates MPOS but not MANG
+		d.registers[MPOS].invalidate()
+		recalc = true
+	case MPOS:
+		// Setting a new MPOS invalidates MANG but not ZPOS
+		d.registers[MANG].invalidate()
+		recalc = true
+	case MANG:
+		// Setting a new MANG invalidates MPOS but not ZPOS
+		d.registers[MPOS].invalidate()
+		recalc = true
+	}
+	if recalc {
+		// Datasheet tells us to wait at least 1ms before reading back
+		time.Sleep(time.Millisecond * 10) // conservative wait
+		return d.calculateEffectiveMaxAngle(address, value)
+	}
+	return nil
+}
+
+// GetMaxPosition returns the 'max position' (MPOS) in different units
+func (d *AS5600Device) GetMaxPosition(units AngleUnit) (uint16, float32, error) {
+	mpos, err := d.ReadRegister(MPOS)
+	if nil != err {
+		return 0, 0.0, err
+	}
+	// Convert to requested units
+	i, f := convertFromNativeAngle(mpos, NATIVE_ANGLE_RANGE, units)
+	return i, f, nil
+}
+
+// SetMaxPosition sets the 'max position' (MPOS) in different units
+func (d *AS5600Device) SetMaxPosition(mpos float32, units AngleUnit) error {
+	return d.WriteRegister(MPOS, convertToNativeAngle(mpos, units))
+}
+
+// GetMaxAngle returns the 'max position' (MANG) in different units
+func (d *AS5600Device) GetMaxAngle(units AngleUnit) (uint16, float32, error) {
+	mang, err := d.ReadRegister(MANG)
+	if nil != err {
+		return 0, 0.0, err
+	}
+	// Convert to requested units
+	i, f := convertFromNativeAngle(mang, NATIVE_ANGLE_RANGE, units)
+	return i, f, nil
+}
+
+// SetMaxAngle sets the 'max angle' (MANG) in different units
+func (d *AS5600Device) SetMaxAngle(mang float32, units AngleUnit) error {
+	return d.WriteRegister(MANG, convertToNativeAngle(mang, units))
+}

as560x/as5601.go

@@ -0,0 +1,22 @@
+//	Product: https://ams.com/as5601
+//	Datasheet: https://ams.com/documents/20143/36005/AS5601_DS000395_3-00.pdf
+
+package as560x // import tinygo.org/x/drivers/ams560x
+
+import "tinygo.org/x/drivers"
+
+// AS5601Device represents an ams AS5601 device driver accessed over I2C
+type AS5601Device struct {
+	BaseDevice // promote base device
+}
+
+// NewAS5601 creates a new AS5601Device given an I2C bus
+func NewAS5601(bus drivers.I2C) AS5601Device {
+	// Create base device
+	baseDev := newBaseDevice(bus)
+	// Add AS5601 specific registers
+	baseDev.registers[ABN] = newI2CRegister(ABN, 0, 0b1111, 1, reg_read|reg_write|reg_program)
+	baseDev.registers[PUSHTHR] = newI2CRegister(PUSHTHR, 0, 0xff, 1, reg_read|reg_write|reg_program)
+	// Return the device
+	return AS5601Device{baseDev}
+}

as560x/as560x.go

@@ -0,0 +1,198 @@
+// Package as560x implements drivers for the ams AS5600/AS5601 on-axis magnetic rotary position sensors
+//
+// Product Pages:
+//	AS5600: https://ams.com/as5600
+//	AS5601: https://ams.com/as5601
+//
+// Datasheets:
+//	AS5600: https://ams.com/documents/20143/36005/AS5600_DS000365_5-00.pdf
+//	AS5601: https://ams.com/documents/20143/36005/AS5601_DS000395_3-00.pdf
+//
+
+package as560x // import tinygo.org/x/drivers/ams560x
+
+import (
+	"errors"
+
+	"tinygo.org/x/drivers"
+)
+
+// Config holds the configuration for the AMS AS560x sensor devices.
+type Config struct {
+	// Address is the I2C address of the AS560x device. If left zero this will default to 0x36
+	Address uint8
+}
+
+// MagnetStrength is an enum to indicate the magnetic field strength detected by the AS560x sensors.
+type MagnetStrength int
+
+const (
+	// MagnetTooWeak indicates that the magnet strength is too weak (AGC maximum gain overflow) - move it closer
+	MagnetTooWeak MagnetStrength = iota - 1
+	// MagnetOk indicates that the magnet strength is about right.
+	MagnetOk
+	// MagnetTooStrong indicates that the magnet strength is too strong (AGC minimum gain overflow) - move it further away
+	MagnetTooStrong
+)
+
+// AngleUnit is an enum to allow the use of different units when reading/writing angles from the AS560x sensors.
+type AngleUnit int
+
+const (
+	// ANGLE_NATIVE uses the device's native angle measurement. i.e. 12-bit integer, 0 <= angle <= 0xfff (4095)
+	ANGLE_NATIVE AngleUnit = iota
+	// ANGLE_DEGREES_INT measures angles in degrees using integer arithmetic for speed. i.e. 0 <= angle < 360
+	ANGLE_DEGREES_INT
+	// ANGLE_DEGREES_FLOAT measures angles in degrees using floating point (slower). i.e. 0.0 <= angle < 360.0
+	ANGLE_DEGREES_FLOAT
+	// ANGLE_RADIANS measures angles in radians using floating point (slower). i.e. 0.0 <= angle < 2 * PI
+	ANGLE_RADIANS
+)
+
+const (
+	// NATIVE_ANGLE_MAX is the maximum valid value for a native angle for a AS560x device
+	NATIVE_ANGLE_MAX = (1 << 12) - 1 + iota
+	// NATIVE_ANGLE_RANGE is the number of unique values for native angles for a AS560x device
+	NATIVE_ANGLE_RANGE
+)
+
+var (
+	errRegisterNotFound = errors.New("Register not found")
+	errMaxBurnAngle     = errors.New("Max BURN_ANGLE limit reached")
+)
+
+// BaseDevice handles the common behaviour between AS5600 & AS5601 devices
+type BaseDevice struct {
+	bus       drivers.I2C
+	address   uint8
+	registers map[uint8]*i2cRegister
+	maxAngle  uint16
+}
+
+// newBaseDevice creates a new base device given an I2C bus.
+func newBaseDevice(bus drivers.I2C) BaseDevice {
+	// Add all 'base' registers, common to both AS5600 & AS5601
+	conf := newI2CRegister(CONF, 0, 0x3fff, 2, reg_read|reg_write|reg_program)
+	status := newI2CRegister(STATUS, 0, 0xff, 1, reg_read)
+	regs := map[uint8]*i2cRegister{
+		ZPOS:      newI2CRegister(ZPOS, 0, 0xfff, 2, reg_read|reg_write|reg_program),
+		CONF:      conf,
+		RAW_ANGLE: newI2CRegister(RAW_ANGLE, 0, 0xfff, 2, reg_read),
+		ANGLE:     newI2CRegister(ANGLE, 0, 0xfff, 2, reg_read),
+		STATUS:    status,
+		AGC:       newI2CRegister(AGC, 0, 0xff, 1, reg_read),
+		MAGNITUDE: newI2CRegister(MAGNITUDE, 0, 0xfff, 2, reg_read),
+		BURN:      newI2CRegister(BURN, 0, 0xff, 1, reg_write),
+		// Add common 'virtual registers' These are bitfields within the common registers above
+		// A virtual register provides a convenient way to access the fields of a registers
+		// by handling all of the necessary bitfield shifting and masking operations
+		WD:   newVirtualRegister(conf, 13, 0b1),
+		FTH:  newVirtualRegister(conf, 10, 0b111),
+		SF:   newVirtualRegister(conf, 8, 0b11),
+		HYST: newVirtualRegister(conf, 2, 0b11),
+		PM:   newVirtualRegister(conf, 0, 0b11),
+		MD:   newVirtualRegister(status, 5, 0b1),
+		ML:   newVirtualRegister(status, 4, 0b1),
+		MH:   newVirtualRegister(status, 3, 0b1),
+	}
+	return BaseDevice{bus, DefaultAddress, regs, NATIVE_ANGLE_RANGE}
+}
+
+// Configure sets up the AMS AS560x sensor device with the given configuration.
+func (d *BaseDevice) Configure(cfg Config) {
+	if cfg.Address == 0 {
+		cfg.Address = DefaultAddress
+	}
+	d.address = cfg.Address
+}
+
+// ReadRegister reads the value for the given register from the AS560x device via I2C
+func (d *BaseDevice) ReadRegister(address uint8) (uint16, error) {
+	reg, ok := d.registers[address]
+	if !ok {
+		return 0, errRegisterNotFound
+	}
+	return reg.read(d.bus, d.address)
+}
+
+// WriteRegister writes the given value for the given register to the AS560x device via I2C
+func (d *BaseDevice) WriteRegister(address uint8, value uint16) error {
+	reg, ok := d.registers[address]
+	if !ok {
+		return errRegisterNotFound
+	}
+	return reg.write(d.bus, d.address, value)
+}
+
+// GetZeroPosition returns the 'zero position' (ZPOS) in various units
+func (d *BaseDevice) GetZeroPosition(units AngleUnit) (uint16, float32, error) {
+	zpos, err := d.ReadRegister(ZPOS)
+	if nil != err {
+		return 0, 0.0, err
+	}
+	// Convert to requested units
+	i, f := convertFromNativeAngle(zpos, NATIVE_ANGLE_RANGE, units)
+	return i, f, nil
+}
+
+// SetZeroPosition sets the 'zero position' (ZPOS) in various units
+func (d *BaseDevice) SetZeroPosition(zpos float32, units AngleUnit) error {
+	return d.WriteRegister(ZPOS, convertToNativeAngle(zpos, units))
+}
+
+// RawAngle reads the (unscaled & unadjusted) RAW_ANGLE register in various units
+func (d *BaseDevice) RawAngle(units AngleUnit) (uint16, float32, error) {
+	angle, err := d.ReadRegister(RAW_ANGLE)
+	if nil != err {
+		return 0, 0.0, err
+	}
+	// Convert to requested units
+	i, f := convertFromNativeAngle(angle, NATIVE_ANGLE_RANGE, units)
+	return i, f, nil
+}
+
+// Angle reads the (scaled & adjusted) ANGLE register in various units
+func (d *BaseDevice) Angle(units AngleUnit) (uint16, float32, error) {
+	// ZPOS enables setting the 'zero position' of the device to any RAW_ANGLE value
+	// ANGLE is RAW_ANGLE adjusted relative to ZPOS.
+	angle, err := d.ReadRegister(ANGLE)
+	if nil != err {
+		return 0, 0.0, err
+	}
+	// Convert to requested units
+	i, f := convertFromNativeAngle(angle, d.maxAngle, units)
+	return i, f, nil
+}
+
+// MagnetStatus reads the STATUS register and reports magnet position characteristics
+func (d *BaseDevice) MagnetStatus() (detected bool, strength MagnetStrength, err error) {
+	status, err := d.ReadRegister(STATUS)
+	if nil != err {
+		return false, MagnetOk, err
+	}
+	detected = (status & STATUS_MD) != 0
+	strength = MagnetOk
+	if (status & STATUS_ML) != 0 {
+		strength = MagnetTooWeak
+	} else if (status & STATUS_MH) != 0 {
+		strength = MagnetTooStrong
+	}
+	return
+}
+
+// Burn is a convenience method to program the device permanently by writing to the BURN register (limited number of times use!)
+func (d *BaseDevice) Burn(burnCmd BURN_CMD) error {
+	if BURN_ANGLE == burnCmd {
+		// BURN_ANGLE can only be executed up to 3 times.
+		// We can check this in advance by reading ZMCO before writing to the BURN register.
+		numBurns, err := d.ReadRegister(ZMCO)
+		if nil != err {
+			return err
+		}
+		if numBurns >= BURN_ANGLE_COUNT_MAX {
+			// We're outta BURNs :(
+			return errMaxBurnAngle
+		}
+	}
+	return d.WriteRegister(BURN, uint16(burnCmd))
+}

as560x/helpers.go

@@ -0,0 +1,95 @@
+package as560x // import tinygo.org/x/drivers/ams560x
+
+import "math"
+
+// convertFromNativeAngle converts and scales an angle from the device's native 12-bit range to the requested units
+func convertFromNativeAngle(angle uint16, maxAngle uint16, units AngleUnit) (uint16, float32) {
+	// MANG == 0 & MANG == NATIVE_ANGLE_RANGE (1 << 12) mean the same thing: use full circle range
+	// but the latter makes the maths/code simpler
+	if 0 == maxAngle {
+		maxAngle = NATIVE_ANGLE_RANGE
+	}
+	switch units {
+	case ANGLE_NATIVE:
+		// For native angles, scaling has already been done by the device
+		return angle, float32(angle)
+	case ANGLE_DEGREES_INT:
+		// Convert to degrees using integer arithmetic. Less accuracy but faster
+		var deg int = 0
+		if NATIVE_ANGLE_RANGE == maxAngle {
+			// Simplify the conversion when using the full range
+			deg = int(angle) * 360 >> 12
+		} else {
+			// Using an integer degrees scale with a narrower native range is pointless since we don't
+			// benefit at all from the increase in native resolution, in fact we LOSE precision.
+			// Alas, we have to return something
+			// First get maxAngle on the degrees scale
+			degMang, _ := convertFromNativeAngle(maxAngle, NATIVE_ANGLE_RANGE, units)
+			// Now scale angle
+			deg = int(angle) * int(degMang) / NATIVE_ANGLE_RANGE
+		}
+		return uint16(deg), float32(deg)
+	case ANGLE_DEGREES_FLOAT:
+		// Convert to degrees using floating point. More accuracy at expense of speed
+		var degF float32 = 0.0
+		if NATIVE_ANGLE_RANGE == maxAngle {
+			// Simplify the conversion when using the full range
+			degF = float32(angle) * 360.0 / NATIVE_ANGLE_RANGE
+		} else {
+			// Scale to degrees using a narrower native range
+			// First get maxAngle on the degrees scale
+			_, degMangF := convertFromNativeAngle(maxAngle, NATIVE_ANGLE_RANGE, units)
+			// Now scale angle
+			degF = float32(angle) * degMangF / NATIVE_ANGLE_RANGE
+		}
+		return uint16(degF), degF
+	case ANGLE_RADIANS:
+		// Convert to radians. Can only be done using floating point.
+		var rad float32 = 0.0
+		if NATIVE_ANGLE_RANGE == maxAngle {
+			// Simplify the conversion when using the full range
+			rad = float32(angle) * 2 * math.Pi / NATIVE_ANGLE_RANGE
+		} else {
+			// Scale to radians using a narrower native range
+			// First get maxAngle on the radians scale
+			_, radMang := convertFromNativeAngle(maxAngle, NATIVE_ANGLE_RANGE, units)
+			// Now scale angle
+			rad = float32(angle) * radMang / NATIVE_ANGLE_RANGE
+		}
+		return uint16(rad), rad
+	default:
+		panic("Unknown angle measurement unit")
+	}
+}
+
+// convertToNativeAngle converts an angle from the requested units to the device's native 12-bit range.
+func convertToNativeAngle(angle float32, units AngleUnit) uint16 {
+	var pos uint16 = 0
+	switch units {
+	case ANGLE_NATIVE:
+		pos = uint16(angle)
+	case ANGLE_DEGREES_INT:
+		fallthrough
+	case ANGLE_DEGREES_FLOAT:
+		// Convert from degrees
+		angle = float32(math.Mod(float64(angle), 360.0))
+		if angle < 0.0 {
+			angle += 360.0
+		}
+		pos = uint16(math.Round(float64(angle) * NATIVE_ANGLE_RANGE / 360.0))
+	case ANGLE_RADIANS:
+		// Convert from radians
+		const circRad = 2.0 * math.Pi
+		angle = float32(math.Mod(float64(angle), circRad))
+		if angle < 0.0 {
+			angle += circRad
+		}
+		pos = uint16(math.Round(float64(angle) * NATIVE_ANGLE_RANGE / circRad))
+	default:
+		panic("Unknown angle measurement unit")
+	}
+	if pos > NATIVE_ANGLE_MAX {
+		pos = NATIVE_ANGLE_MAX
+	}
+	return pos
+}

as560x/i2c_register.go

@@ -0,0 +1,169 @@
+package as560x // import tinygo.org/x/drivers/ams560x
+
+import (
+	"encoding/binary"
+	"errors"
+
+	"tinygo.org/x/drivers"
+)
+
+// registerAttributes is a bitfield of attributes for a register
+type registerAttributes uint8
+
+const (
+	// reg_read indicates that the register is readable
+	reg_read registerAttributes = 1 << iota
+	// reg_write indicates that the register is writeable
+	reg_write
+	// reg_program indicates that the register can be permanently programmed ('BURNed')
+	reg_program
+)
+
+var (
+	errRegisterNotReadable  = errors.New("Register is not readable")
+	errRegisterNotWriteable = errors.New("Register is not writeable")
+)
+
+// i2cRegister encapsulates the address, structure and read/write logic for a register on a AS560x device
+type i2cRegister struct {
+	// host is the 'host register' for virtual registers. Physical/root registers have this set to self
+	host *i2cRegister
+	// address is the i2c address of the register. For 2-byte (word) addresses it's the low byte which holds the MSBs
+	address uint8
+	// shift is the number of bits the value is 'left shifted' into the register byte/word (0-15)
+	shift uint16
+	// mask is a bitwise mask applied to the register AFTER 'right shifting' to mask the register value
+	mask uint16
+	// num_bytes is the width of the register in bytes, 1 or 2.
+	num_bytes uint8
+	// attributes holds the register attributes. A bitfield of REG_xyz constants
+	attributes registerAttributes
+	// cached indicates whether we are holding a cached value of the register in value
+	cached bool
+	// value can be used as a 'cache' of the register's value for writeable registers.
+	value uint16
+}
+
+// newI2CRegister returns a pointer to a new i2cRegister with no cached value
+func newI2CRegister(address uint8, shift uint16, mask uint16, num_bytes uint8, attributes registerAttributes) *i2cRegister {
+	reg := &i2cRegister{
+		address:    address,
+		shift:      shift,
+		mask:       mask,
+		num_bytes:  num_bytes,
+		attributes: attributes,
+	}
+	// root registers host themselves
+	reg.host = reg
+	return reg
+}
+
+// newVirtualRegister returns a pointer to a new i2cRegister with the given host register and shift/mask.
+func newVirtualRegister(host *i2cRegister, shift uint16, mask uint16) *i2cRegister {
+	return &i2cRegister{
+		host:       host,
+		address:    host.address,
+		shift:      shift,
+		mask:       mask,
+		num_bytes:  host.num_bytes,
+		attributes: host.attributes,
+	}
+}
+
+// invalidate invalidates any cached value for the register and forces an I2C read on the next read()
+func (r *i2cRegister) invalidate() {
+	r.host.cached = false
+	r.host.value = 0
+}
+
+// readShiftAndMask is an internal method to read a value for the register over the given I2C bus from the device with the given address applying the given shift and mask
+func (r *i2cRegister) readShiftAndMask(bus drivers.I2C, deviceAddress uint8, shift uint16, mask uint16) (uint16, error) {
+	if r.host.attributes&reg_read == 0 {
+		return 0, errRegisterNotReadable
+	}
+
+	// Only read over I2C if we don't have the host register value cached
+	var val uint16 = r.host.value
+	if !r.host.cached {
+		// To avoid an alloc we always use an array of 2 bytes
+		var buffer [2]byte
+		var buf []byte
+		if r.host.num_bytes < 2 {
+			buf = buffer[:1]
+		} else {
+			buf = buffer[:]
+		}
+		// Read the host register over I2C
+		err := bus.ReadRegister(deviceAddress, r.host.address, buf)
+		if nil != err {
+			return 0, err
+		}
+		// Unpack data from I2C
+		if r.host.num_bytes > 1 {
+			val = binary.BigEndian.Uint16(buf)
+		} else {
+			val = uint16(buf[0])
+		}
+		// cache this value if the host register is writeable. Note we cache the entire buffer without applying shift/mask
+		if r.host.attributes&reg_write != 0 {
+			r.host.value = val
+			r.host.cached = true
+		}
+	}
+	// Shift and mask the value before returning
+	val >>= shift
+	val &= mask
+	return val, nil
+}
+
+// read reads a value for the register over the given I2C bus from the device with the given address.
+func (r *i2cRegister) read(bus drivers.I2C, deviceAddress uint8) (uint16, error) {
+	return r.readShiftAndMask(bus, deviceAddress, r.shift, r.mask)
+}
+
+// write writes a value for the register over the given I2C bus to the device with the given address.
+func (r *i2cRegister) write(bus drivers.I2C, deviceAddress uint8, value uint16) error {
+	if r.host.attributes&reg_write == 0 {
+		return errRegisterNotWriteable
+	}
+	var newValue uint16 = 0
+	// Data sheet tells us to do a read first, modify only the desired bits and then write back
+	// since (quote:) 'Blank fields may contain factory settings'
+	// We will also need to do this anyway to support virtualRegister mappings on some registers
+	// (e.g. CONF/STATUS)
+	if (r.host.attributes & reg_read) > 0 { // not all registers are readable, e.g. BURN
+		// read the host register's entire host byte/word, regardless of shift & mask
+		readValue, error := r.readShiftAndMask(bus, deviceAddress, 0, 0xffff)
+		if error != nil {
+			return error
+		}
+		// Zero-out ONLY the relevant bits in newValue we just read
+		readValue &= (0xffff ^ (r.mask << r.shift))
+		newValue = readValue
+	}
+	// Mask the new value and shift it into place
+	value &= r.mask
+	value <<= r.shift
+	// OR the masked & shifted value back into newValue to be written
+	newValue |= value
+	// Pack newValue into a byte buffer to write. To avoid an alloc we always use an array of 2 bytes
+	var buffer [2]byte
+	var buf []byte
+	if r.host.num_bytes < 2 {
+		buf = buffer[:1]
+		buf[0] = uint8(newValue & 0xff)
+	} else {
+		buf = buffer[:]
+		binary.BigEndian.PutUint16(buf, newValue)
+	}
+
+	// Write the register from the buffer over I2C
+	err := bus.WriteRegister(deviceAddress, r.host.address, buf)
+	// after successful I2C write, cache this value if the host register (if also readable)
+	// Note we cache the entire buffer without applying shift/mask
+	if nil == err && r.host.attributes&reg_read != 0 {
+		r.host.value = newValue
+		r.host.cached = true
+	}
+	return err
+}

as560x/registers.go

@@ -0,0 +1,208 @@
+package as560x // import tinygo.org/x/drivers/ams560x
+
+// DefaultAddress is the default I2C address of the AMS AS560x sensors (0x36).
+const DefaultAddress uint8 = 0x36
+
+// AS560x common device registers
+const (
+	// ZMCO contains the number of times a BURN_ANGLE command has been executed (max 3 burns)
+	ZMCO = 0x00
+	// ZPOS is the zero (start) position in RAW_ANGLE terms.
+	ZPOS = 0x01
+	// CONF supports custom config. Raw 14-bit register. See datasheet for mapping or use 'virtual registers' below.
+	CONF = 0x07
+	// STATUS indicates magnet position. Encapsulates MD, ML & MH. See also 'virtual registers' below.
+	STATUS = 0x0b
+	// RAW_ANGLE is the raw unscaled & unadjusted angle (12 bit: 0-4095/0xfff)
+	RAW_ANGLE = 0x0c
+	// ANGLE is RAW_ANGLE scaled & adjusted according to ZPOS (and MPOS/MANG on AS5600). (12 bit: 0-4095/0xfff)
+	ANGLE = 0x0e
+	// AGC is the Automatic Gain Control based on temp, airgap etc. 0-255 @ 5V, 0-128 @ 3.3V.
+	AGC = 0x1a
+	// MAGNITUDE indicates the magnitude value of the internal CORDIC output. See datasheet for more info.
+	MAGNITUDE = 0x1b
+	// BURN performs permanent programming of some registers. See BURN_XYZ cmd constants below for commands.
+	BURN = 0xff
+)
+
+// AS5600 specific registers
+const (
+	// MPOS is the maximum position in RAW_ANGLE terms. With ZPOS, defines a 'narrower angle' for higher resolution.
+	MPOS = 0x03
+	// MANG is the maximum angle. With ZPOS, defines a 'narrower angle' for higher resolution.
+	MANG = 0x05
+)
+
+// AS5601 specific registers
+const (
+	// ABN. See datasheet for mapping
+	ABN = 0x09
+	// PUSHTHR. Configures push-button function. See datasheet and AGC
+	PUSHTHR = 0x0a
+)
+
+// 'Virtual Registers' (VRs) are bitfields within the registers above.
+// These are not real register addresses recognized by the chip,
+// but they are recognized by the driver for convenience.
+
+// virtualRegisterStartAddress defines the start of the virtual register address range.
+const virtualRegisterStartAddress = 0xa0
+
+const (
+	// VRs for CONF
+
+	// WD is a Virtual Register for the Watchdog timer. See WATCHDOG_TIMER consts.
+	WD = iota + virtualRegisterStartAddress
+	// FTH is a Virtual Register for the Fast Filter Threshold. See FAST_FILTER_THRESHOLD consts.
+	FTH
+	// SF is a Virtual Register for the Slow Filter. See SLOW_FILTER_RESPONSE consts.
+	SF
+	// PWMF is a Virtual Register for PWM Frequency (AS5600 ONLY). See PWM_FREQUENCY consts.
+	PWMF
+	// OUTS is a Virtual Register for the Output Stage (AS5600 ONLY). See OUTPUT_STAGE consts.
+	OUTS
+	// HYST is a Virtual Register for Hysteresis. See HYSTERESIS consts.
+	HYST
+	// PM is a Virtual Register for the Power Mode. See POWER_MODE consts.
+	PM
+
+	// VRs for STATUS (0 = unset, 1 = set)
+
+	// MD is a Virtual Register for the 'Magnet was detected' flag.
+	MD
+	// ML is a Virtual Register for the 'AGC maximum gain overflow' a.k.a 'magnet too weak' flag.
+	ML
+	// MH is a Virtual Register for the 'AGC minimum gain overflow' a.k.a 'magnet too strong' flag.
+	MH
+)
+
+// POWER_MODE values for the PM component of CONF (and the PM VR)
+const (
+	// PM_NOM is the normal 'always on' power mode. No polling, max 6.5mA current
+	PM_NOM = iota
+	// PM_LPM1 is Low Power Mode 1. 5ms polling, max 3.4mA current
+	PM_LPM1
+	// PM_LPM2 is Low Power Mode 2. 20ms polling, max 1.8mA current
+	PM_LPM2
+	// PM_LPM3 is Low Power Mode 3. 100ms polling, max 1.5mA current
+	PM_LPM3
+)
+
+// HYSTERESIS values for the HYST component of CONF (and the HYST VR)
+const (
+	// HYST_OFF disables any hysteresis of the output
+	HYST_OFF = iota
+	// HYST_1LSB enables output hysteresis using 1 LSB
+	HYST_1LSB
+	// HYST_2LSB enables output hysteresis using 2 LSBs
+	HYST_2LSB
+	// HYST_3LSB enables output hysteresis using 3 LSBs
+	HYST_3LSB
+)
+
+// OUTPUT_STAGE values for the OUTS component of CONF (and the OUTS VR - AS5600 ONLY)
+const (
+	// OS_ANALOG_FULL_RANGE enables analog output with full range (0%-100% VDD)
+	OS_ANALOG_FULL_RANGE = iota
+	// OS_ANALOG_REDUCED_RANGE enables analog output with reduced range (10%-90% VDD)
+	OS_ANALOG_REDUCED_RANGE
+	// OS_DIGITAL_PWM enables digital PWM output. Frequency determined by PWMF
+	OS_DIGITAL_PWM
+)
+
+// PWM_FREQUENCY values for the PWMF component of CONF (and the PWMF VR - ASS5600 ONLY)
+const (
+	// PWMF_115_HZ enables PWM at 115 Hz
+	PWMF_115_HZ = iota
+	// PWMF_230_HZ enables PWM at 230 Hz
+	PWMF_230_HZ
+	// PWMF_460_HZ enables PWM at 460 Hz
+	PWMF_460_HZ
+	// PWMF_920_HZ enables PWM at 920 Hz
+	PWMF_920_HZ
+)
+
+// SLOW_FILTER_RESPONSE values for the SF (slow filter) component of CONF (and the SF VR)
+const (
+	// SF_16X enables a 16x Slow Filter step response
+	SF_16X = iota
+	// SF_8X enables a 8x Slow Filter step response
+	SF_8X
+	// SF_4X enables a 4x Slow Filter step response
+	SF_4X
+	// SF_2X enables a 2x Slow Filter step response
+	SF_2X
+)
+
+// FAST_FILTER_THRESHOLD values for the FTH (fast filter threshold) component of CONF (and the FTH VR)
+const (
+	// FTH_NONE disables the fast filter (slow filter only)
+	FTH_NONE = iota
+	// FTH_6LSB enables a fast filter threshold with 6 LSBs
+	FTH_6LSB
+	// FTH_7LSB enables a fast filter threshold with 7 LSBs
+	FTH_7LSB
+	// FTH_9LSB enables a fast filter threshold with 9 LSBs
+	FTH_9LSB
+	// FTH_18LSB enables a fast filter threshold with 18 LSBs
+	FTH_18LSB
+	// FTH_21LSB enables a fast filter threshold with 21 LSBs
+	FTH_21LSB
+	// FTH_24LSB enables a fast filter threshold with 24 LSBs
+	FTH_24SB
+	// FTH_10LSB enables a fast filter threshold with 10 LSBs
+	FTH_10LSB
+)
+
+// WATCHDOG_TIMER values for the WD component of CONF (and the WD VR)
+const (
+	// WD_OFF disables the Watchdog Timer
+	WD_OFF = iota
+	// WD_ON enables the Watchdog Timer (automatic entry into LPM3 low-power mode enabled)
+	WD_ON
+)
+
+// constants for the raw STATUS register bitfield value.
+const (
+	// STATUS_MH is set in STATUS when the magnet field is too strong (AGC minimum gain overflow)
+	STATUS_MH = 1 << (iota + 3)
+	// STATUS_ML is set in STATUS when the magnet field is too weak (AGC maximum gain overflow)
+	STATUS_ML
+	// STATUS_MD is set n STATUS when the magnet is detected. Doesn't seem to work with some units.
+	STATUS_MD
+)
+
+// ABN_MAPPING values for the ABN register (AS5601 ONLY)
+const (
+	// ABN_8 configures 8 output positions (61 Hz)
+	ABN_8 = iota
+	// ABN_16 configures 16 output positions (122 Hz)
+	ABN_16
+	// ABN_32 configures 32 output positions (244 Hz)
+	ABN_32
+	// ABN_64 configures 64 output positions (488 Hz)
+	ABN_64
+	// ABN_128 configures 128 output positions (976 Hz)
+	ABN_128
+	// ABN_256 configures 256 output positions (1.95 KHz)
+	ABN_256
+	// ABN_512 configures 512 output positions (3.9 KHz)
+	ABN_512
+	// ABN_1024 configures 1024 output positions (7.8 KHz)
+	ABN_1024
+	// ABN_2048 configures 2048 output positions (15.6 KHz)
+	ABN_2048
+)
+
+// BURN_CMD is a command to write to the BURN register.
+type BURN_CMD uint16
+
+const (
+	// BURN_ANGLE is the value to write to BURN to permanently program ZPOS & MPOS (Max 3 times!)
+	BURN_ANGLE BURN_CMD = 0x80
+	// BURN_SETTING is the value to write to BURN to permanently program MANG & CONF (ONCE ONLY!)
+	BURN_SETTING BURN_CMD = 0x40
+)
+
+// BURN_ANGLE_COUNT_MAX is a constant for the maximum number of times a BURN_ANGLE command can be executed. Compare this with ZMCO
+const BURN_ANGLE_COUNT_MAX uint16 = 3

examples/as560x/main.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"machine"
+	"machine/usb/hid/mouse"
+	"math"
+	"time"
+
+	"tinygo.org/x/drivers/as560x"
+)
+
+func main() {
+	// Let's use the AS5600 to make the world's most useless mouse with just a single X-axis & no buttons (!)
+	machine.I2C0.Configure(machine.I2CConfig{
+		Frequency: machine.TWI_FREQ_400KHZ,
+		SDA:       machine.GPIO4,
+		SCL:       machine.GPIO5,
+	})
+	as5600 := as560x.NewAS5600(machine.I2C0)
+	as5600.Configure(as560x.Config{})
+	mouse := mouse.New()
+
+	lastAngle := -1
+	for {
+		time.Sleep(time.Millisecond * 10)
+		// Get the magnet status of the AS5600
+		magnetDetected, magnetStrength, err := as5600.MagnetStatus()
+		if err != nil {
+			continue
+		}
+		// Get the raw angle from the AS5600
+		angle, _, err := as5600.RawAngle(as560x.ANGLE_NATIVE)
+		if err != nil {
+			continue
+		}
+		str := ""
+		if !magnetDetected {
+			str += "NOT "
+		}
+		str += "detected. Strength is "
+		switch magnetStrength {
+		case as560x.MagnetTooWeak:
+			str += "too weak"
+		case as560x.MagnetTooStrong:
+			str += "too strong"
+		default:
+			str += "ok"
+		}
+		println("Raw angle:", angle, "Magnet was", str)
+		if lastAngle != -1 {
+			diff := int(angle) - lastAngle
+			// correct the zero crossover glitch
+			if diff < -0xc00 {
+				diff += 0xfff
+			} else if diff > 0xc00 {
+				diff -= 0xfff
+			}
+			// debounce the noise (could use the sensor's filters/hysteresis instead?)
+			if math.Abs(float64(diff)) > 2 {
+				// move the mouse x-axis in response to the AS5600
+				mouse.Move(diff, 0)
+			}
+		}
+		lastAngle = int(angle)
+	}
+}