Add ens160 i2c driver

Driver for ENS160 sensor:
https://www.sciosense.com/wp-content/uploads/2023/12/ENS160-Datasheet.pdf

ens160/ens160.go

@@ -0,0 +1,225 @@
+// Package ens160 provides a driver for the ScioSense ENS160 digital gas sensor.
+//
+// Datasheet: https://www.sciosense.com/wp-content/uploads/2023/12/ENS160-Datasheet.pdf
+package ens160
+
+import (
+	"encoding/binary"
+	"errors"
+	"time"
+
+	"tinygo.org/x/drivers"
+)
+
+const (
+	defaultTimeout = 30 * time.Millisecond
+	shortTimeout   = 1 * time.Millisecond
+)
+
+// Conversion constants for environment data compensation.
+const (
+	kelvinOffsetMilli = 273150          // 273.15 K in milli-units
+	tempRawFactor     = 64              // As per datasheet for TEMP_IN
+	humRawFactor      = 512             // As per datasheet for RH_IN
+	milliFactor       = 1000            // For converting from milli-units
+	roundingTerm      = milliFactor / 2 // For rounding before integer division
+)
+
+// validityStrings provides human-readable descriptions for validity flags.
+var validityStrings = [...]string{
+	ValidityNormalOperation:     "normal operation",
+	ValidityWarmUpPhase:         "warm-up phase, wait ~3 minutes for valid data",
+	ValidityInitialStartUpPhase: "initial start-up phase, wait ~1 hour for valid data",
+	ValidityInvalidOutput:       "invalid output",
+}
+
+// Device wraps an I2C connection to an ENS160 device.
+type Device struct {
+	bus  drivers.I2C // I²C implementation
+	addr uint16      // 7‑bit bus address, promoted to uint16 per drivers.I2C
+
+	// shadow registers / last measurements
+	lastTvocPPB  uint16
+	lastEco2PPM  uint16
+	lastAqiUBA   uint8
+	lastValidity uint8 // Store the latest validity status
+
+	// pre‑allocated buffers
+	wbuf [5]byte // longest write: reg + 4 bytes (TEMP+RH)
+	rbuf [5]byte // longest read: DATA burst (5 bytes)
+}
+
+// New returns a new ENS160 driver.
+func New(bus drivers.I2C, addr uint16) *Device {
+	if addr == 0 {
+		addr = DefaultAddress
+	}
+	return &Device{
+		bus:          bus,
+		addr:         addr,
+		lastValidity: ValidityInvalidOutput,
+	}
+}
+
+// Connected returns whether a ENS160 has been found.
+func (d *Device) Connected() bool {
+	d.wbuf[0] = regPartID
+	err := d.bus.Tx(d.addr, d.wbuf[:1], d.rbuf[:2])
+	return err == nil && d.rbuf[0] == LowPartID && d.rbuf[1] == HighPartID
+}
+
+// Configure sets up the device for reading.
+func (d *Device) Configure() error {
+	// 1. Soft-reset. The device will automatically enter IDLE mode.
+	if err := d.write1(regOpMode, ModeReset); err != nil {
+		return err
+	}
+	time.Sleep(defaultTimeout)
+
+	// 2. Clear GPR registers, then go to STANDARD mode.
+	if err := d.write1(regCommand, cmdClrGPR); err != nil {
+		return err
+	}
+	time.Sleep(defaultTimeout)
+
+	if err := d.write1(regOpMode, ModeStandard); err != nil {
+		return err
+	}
+	time.Sleep(defaultTimeout)
+
+	return nil
+}
+
+// calculateTempRaw converts temperature from milli-degrees Celsius to the sensor's raw format.
+func calculateTempRaw(tempMilliC int32) uint16 {
+	// Clip temperature
+	const (
+		minC = -40 * 1000
+		maxC = 85 * 1000
+	)
+	if tempMilliC < minC {
+		tempMilliC = minC
+	} else if tempMilliC > maxC {
+		tempMilliC = maxC
+	}
+
+	// Integer fixed-point conversion to format required by the sensor.
+	// Formula from datasheet: T_IN = (T_ambient_C + 273.15) * 64
+	return uint16((((tempMilliC + kelvinOffsetMilli) * tempRawFactor) + roundingTerm) / milliFactor)
+}
+
+// calculateHumRaw converts relative humidity from milli-percent to the sensor's raw format.
+func calculateHumRaw(rhMilliPct int32) uint16 {
+	// Clip humidity
+	if rhMilliPct < 0 {
+		rhMilliPct = 0
+	} else if rhMilliPct > 100*1000 {
+		rhMilliPct = 100 * 1000
+	}
+
+	// Integer fixed-point conversion to format required by the sensor.
+	// Formula from datasheet: RH_IN = (RH_ambient_% * 512)
+	return uint16(((rhMilliPct * humRawFactor) + roundingTerm) / milliFactor)
+}
+
+// SetEnvDataMilli sets the ambient temperature and humidity for compensation.
+//
+// tempMilliC is the temperature in milli-degrees Celsius.
+// rhMilliPct is the relative humidity in milli-percent.
+func (d *Device) SetEnvDataMilli(tempMilliC, rhMilliPct int32) error {
+	tempRaw := calculateTempRaw(tempMilliC)
+	humRaw := calculateHumRaw(rhMilliPct)
+
+	d.wbuf[0] = regTempIn // start address (auto‑increment)
+	binary.LittleEndian.PutUint16(d.wbuf[1:3], tempRaw)
+	binary.LittleEndian.PutUint16(d.wbuf[3:5], humRaw)
+
+	return d.bus.Tx(d.addr, d.wbuf[:5], nil)
+}
+
+// Update refreshes the concentration measurements.
+func (d *Device) Update(which drivers.Measurement) error {
+	if which&drivers.Concentration == 0 {
+		return nil // nothing requested
+	}
+
+	const maxTries = 1000
+	var (
+		status   uint8
+		validity uint8
+	)
+	var gotData bool
+
+	// Poll DEVICE_STATUS until NEWDAT or timeout
+	for range maxTries {
+		var err error
+		status, err = d.read1(regStatus)
+		if err != nil {
+			return err
+		}
+		if status&statusSTATER != 0 {
+			return errors.New("ENS160: error (STATER set)")
+		}
+		validity = (status & statusValidityMask) >> statusValidityShift
+
+		if status&statusNEWDAT != 0 {
+			gotData = true
+			break // Always break when data available
+		}
+		time.Sleep(shortTimeout)
+	}
+	if !gotData {
+		return errors.New("ENS160: timeout waiting for NEWDAT")
+	}
+
+	// Burst-read data regardless of validity state
+	d.wbuf[0] = regAQI
+	if err := d.bus.Tx(d.addr, d.wbuf[:1], d.rbuf[:5]); err != nil {
+		return errors.New("ENS160: burst read failed")
+	}
+
+	d.lastAqiUBA = d.rbuf[0]
+	d.lastTvocPPB = binary.LittleEndian.Uint16(d.rbuf[1:3])
+	d.lastEco2PPM = binary.LittleEndian.Uint16(d.rbuf[3:5])
+	d.lastValidity = validity // Store the validity status
+
+	return nil
+}
+
+// TVOC returns the last total‑VOC concentration in parts‑per‑billion.
+func (d *Device) TVOC() uint16 { return d.lastTvocPPB }
+
+// ECO2 returns the last equivalent CO₂ concentration in parts‑per‑million.
+func (d *Device) ECO2() uint16 { return d.lastEco2PPM }
+
+// AQI returns the last Air‑Quality Index according to UBA (1–5).
+func (d *Device) AQI() uint8 { return d.lastAqiUBA }
+
+// Validity returns the current operating state of the sensor.
+func (d *Device) Validity() uint8 {
+	return d.lastValidity
+}
+
+// ValidityString returns a human-readable string describing the current validity status.
+func (d *Device) ValidityString() string {
+	if int(d.lastValidity) < len(validityStrings) {
+		return validityStrings[d.lastValidity]
+	}
+	return "unknown"
+}
+
+// write1 writes a single byte to a register.
+func (d *Device) write1(reg, val uint8) error {
+	d.wbuf[0] = reg
+	d.wbuf[1] = val
+	return d.bus.Tx(d.addr, d.wbuf[:2], nil)
+}
+
+// read1 reads a single byte from a register.
+func (d *Device) read1(reg uint8) (uint8, error) {
+	d.wbuf[0] = reg
+	if err := d.bus.Tx(d.addr, d.wbuf[:1], d.rbuf[:1]); err != nil {
+		return 0, err
+	}
+	return d.rbuf[0], nil
+}