change how APDS is interacted with at a I/O level; eliminate heap allocs

apds9960/apds9960.go

@@ -17,6 +17,8 @@ type Device struct {
 	Address uint8
 	mode    uint8
 	gesture gestureData
+	buf     [32]byte
+	_txerr  error
 }
 
 // Configuration for APDS-9960 device.
@@ -57,6 +59,25 @@ type enableConfig struct {
 	PON  bool
 }
 
+type encfg uint8
+
+// data := []byte{gen<<6 | pien<<5 | aien<<4 | wen<<3 | pen<<2 | aen<<1 | pon}
+const (
+	enPON encfg = 1 << iota
+	enAEN
+	enPEN
+	enWEN
+	enAIEN
+	enPIEN
+	enGEN
+)
+
+func (e encfg) write7bits(b []byte) {
+	for i := uint8(0); i < 7; i++ {
+		b[i] = byte(e>>(6-i)) & 1
+	}
+}
+
 // New creates a new APDS-9960 connection. The I2C bus must already be
 // configured.
 //
@@ -68,9 +89,8 @@ func New(bus drivers.I2C) Device {
 // Connected returns whether APDS-9960 has been found.
 // It does a "who am I" request and checks the response.
 func (d *Device) Connected() bool {
-	data := []byte{0}
+	d.txNew()
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_ID_REG, data)
+	return d.txRead8(APDS9960_ID_REG) == 0xAB && d.txErr() == nil
-	return data[0] == 0xAB
 }
 
 // GetMode returns current engine mode
@@ -79,56 +99,73 @@ func (d *Device) GetMode() uint8 {
 }
 
 // DisableAll turns off the device and all functions
-func (d *Device) DisableAll() {
+func (d *Device) DisableAll() error {
-	d.enable(enableConfig{})
+	err := d.enable(0)
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_GCONF4_REG, []byte{0x00})
+	if err != nil {
-	d.mode = MODE_NONE
+		return err
-	d.gesture.detected = GESTURE_NONE
+	}
+	d.txWrite8(APDS9960_GCONF4_REG, 0)
+	err = d.txErr()
+	if err == nil {
+		d.mode = MODE_NONE
+		d.gesture.detected = GESTURE_NONE
+	}
+	return err
 }
 
 // SetProximityPulse sets proximity pulse length (4, 8, 16, 32) and count (1~64)
 // default: 16, 64
-func (d *Device) SetProximityPulse(length, count uint8) {
+func (d *Device) SetProximityPulse(length, count uint8) error {
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_PPULSE_REG, []byte{getPulseLength(length)<<6 | getPulseCount(count)})
+	d.txNew()
+	d.txWrite8(APDS9960_PPULSE_REG, getPulseLength(length)<<6|getPulseCount(count))
+	return d.txErr()
 }
 
 // SetGesturePulse sets gesture pulse length (4, 8, 16, 32) and count (1~64)
 // default: 16, 64
-func (d *Device) SetGesturePulse(length, count uint8) {
+func (d *Device) SetGesturePulse(length, count uint8) error {
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_GPULSE_REG, []byte{getPulseLength(length)<<6 | getPulseCount(count)})
+	d.txNew()
+	d.txWrite8(APDS9960_GPULSE_REG, getPulseLength(length)<<6|getPulseCount(count))
+	return d.txErr()
 }
 
 // SetADCIntegrationCycles sets ALS/color ADC internal integration cycles (1~256, 1 cycle = 2.78 ms)
 // default: 4 (~10 ms)
-func (d *Device) SetADCIntegrationCycles(cycles uint16) {
+func (d *Device) SetADCIntegrationCycles(cycles uint16) error {
 	if cycles > 256 {
 		cycles = 256
 	}
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_ATIME_REG, []byte{uint8(256 - cycles)})
+	d.txNew()
+	d.txWrite8(APDS9960_ATIME_REG, uint8(256-cycles))
+	return d.txErr()
 }
 
 // SetGains sets proximity/gesture gain (1, 2, 4, 8x) and ALS/color gain (1, 4, 16, 64x)
 // default: 1, 1, 4
-func (d *Device) SetGains(proximityGain, gestureGain, colorGain uint8) {
+func (d *Device) SetGains(proximityGain, gestureGain, colorGain uint8) error {
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_CONTROL_REG, []byte{getProximityGain(proximityGain)<<2 | getALSGain(colorGain)})
+	d.txNew()
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_GCONF2_REG, []byte{getProximityGain(gestureGain) << 5})
+	d.txWrite8(APDS9960_CONTROL_REG, getProximityGain(proximityGain)<<2|getALSGain(colorGain))
+	d.txWrite8(APDS9960_GCONF2_REG, getProximityGain(gestureGain)<<5)
+	return d.txErr()
 }
 
 // LEDBoost sets proximity and gesture LED current level (100, 150, 200, 300 (%))
 // default: 100
-func (d *Device) LEDBoost(percent uint16) {
+func (d *Device) LEDBoost(percent uint16) error {
 	var v uint8
-	switch percent {
+	switch {
-	case 100:
+	case percent < 125:
 		v = 0
-	case 150:
+	case percent < 175:
 		v = 1
-	case 200:
+	case percent < 250:
 		v = 2
-	case 300:
+	default:
-		v = 3
+		v = 3 // Maximum case.
 	}
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_CONFIG2_REG, []byte{0x01 | v<<4})
+	d.txNew()
+	d.txWrite8(APDS9960_CONFIG2_REG, 0x01|(v<<4))
+	return d.txErr()
 }
 
 // Setthreshold sets threshold (0~255) for detecting gestures
@@ -147,20 +184,27 @@ func (d *Device) Setsensitivity(s uint8) {
 }
 
 // EnableProximity starts the proximity engine
-func (d *Device) EnableProximity() {
+func (d *Device) EnableProximity() error {
 	if d.mode != MODE_NONE {
-		d.DisableAll()
+		err := d.DisableAll()
+		if err != nil {
+			return err
+		}
 	}
-	d.enable(enableConfig{PON: true, PEN: true, WEN: true})
+	err := d.enable(enPON | enPEN | enWEN)
-	d.mode = MODE_PROXIMITY
+	if err == nil {
+		d.mode = MODE_PROXIMITY
+	}
+	return err
 }
 
 // ProximityAvailable reports if proximity data is available
 func (d *Device) ProximityAvailable() bool {
-	if d.mode == MODE_PROXIMITY && d.readStatus("PVALID") {
+	if d.mode != MODE_PROXIMITY {
-		return true
+		return false
 	}
-	return false
+	status, err := d.ReadStatus()
+	return err == nil && status.PVALID()
 }
 
 // ReadProximity reads proximity data (0~255)
@@ -168,26 +212,30 @@ func (d *Device) ReadProximity() (proximity int32) {
 	if d.mode != MODE_PROXIMITY {
 		return 0
 	}
-	data := []byte{0}
+	d.txNew()
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_PDATA_REG, data)
+	val := d.txRead8(APDS9960_PDATA_REG)
-	return 255 - int32(data[0])
+	return 255 - int32(val)
 }
 
 // EnableColor starts the color engine
-func (d *Device) EnableColor() {
+func (d *Device) EnableColor() error {
 	if d.mode != MODE_NONE {
 		d.DisableAll()
 	}
-	d.enable(enableConfig{PON: true, AEN: true, WEN: true})
+	err := d.enable(enPON | enAEN | enWEN)
-	d.mode = MODE_COLOR
+	if err == nil {
+		d.mode = MODE_COLOR
+	}
+	return err
 }
 
 // ColorAvailable reports if color data is available
 func (d *Device) ColorAvailable() bool {
-	if d.mode == MODE_COLOR && d.readStatus("AVALID") {
+	if d.mode != MODE_COLOR {
-		return true
+		return false
 	}
-	return false
+	status, err := d.ReadStatus()
+	return err == nil && status.AVALID()
 }
 
 // ReadColor reads color data (red, green, blue, clear color/brightness)
@@ -195,28 +243,36 @@ func (d *Device) ReadColor() (r int32, g int32, b int32, clear int32) {
 	if d.mode != MODE_COLOR {
 		return
 	}
-	data := []byte{0, 0, 0, 0, 0, 0, 0, 0}
+	d.txNew()
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_CDATAL_REG, data[:1])
+	data := d.buf[:8]
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_CDATAH_REG, data[1:2])
+	const numLowRegs = APDS9960_GDATAH_REG - APDS9960_CDATAL_REG + 1
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_RDATAL_REG, data[2:3])
+	for i := uint8(0); i < numLowRegs; i++ {
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_RDATAH_REG, data[3:4])
+		data[i] = d.txRead8(i + APDS9960_CDATAL_REG)
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_GDATAL_REG, data[4:5])
+	}
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_GDATAH_REG, data[5:6])
+	data[numLowRegs] = d.txRead8(APDS9960_BDATAL_REG)
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_BDATAL_REG, data[6:7])
+	data[numLowRegs+1] = d.txRead8(APDS9960_BDATAH_REG)
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_BDATAH_REG, data[7:])
+	if d.txErr() != nil {
+		return
+	}
 	clear = int32(uint16(data[1])<<8 | uint16(data[0]))
 	r = int32(uint16(data[3])<<8 | uint16(data[2]))
 	g = int32(uint16(data[5])<<8 | uint16(data[4]))
 	b = int32(uint16(data[7])<<8 | uint16(data[6]))
-	return
+	return r, g, b, clear
 }
 
 // EnableGesture starts the gesture engine
-func (d *Device) EnableGesture() {
+func (d *Device) EnableGesture() error {
 	if d.mode != MODE_NONE {
-		d.DisableAll()
+		err := d.DisableAll()
+		if err != nil {
+			return err
+		}
+	}
+	err := d.enable(enPON | enPEN | enGEN | enWEN)
+	if err != nil {
+		return err
 	}
-	d.enable(enableConfig{PON: true, PEN: true, GEN: true, WEN: true})
 	d.mode = MODE_GESTURE
 	d.gesture.detected = GESTURE_NONE
 	d.gesture.gXDelta = 0
@@ -224,6 +280,7 @@ func (d *Device) EnableGesture() {
 	d.gesture.gXPrevDelta = 0
 	d.gesture.gYPrevDelta = 0
 	d.gesture.received = false
+	return nil
 }
 
 // GestureAvailable reports if gesture data is available
@@ -231,22 +288,16 @@ func (d *Device) GestureAvailable() bool {
 	if d.mode != MODE_GESTURE {
 		return false
 	}
-
+	d.txNew()
-	data := []byte{0, 0, 0, 0}
+	gstatus := d.txRead8(APDS9960_GSTATUS_REG)
-
+	if gstatus&1 == 0 {
-	// check GVALID
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_GSTATUS_REG, data[:1])
-	if data[0]&0x01 == 0 {
 		return false
 	}
-
+	availableDataSets := d.txRead8(APDS9960_GFLVL_REG)
-	// get number of data sets available in FIFO
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_GFLVL_REG, data[:1])
-	availableDataSets := data[0]
 	if availableDataSets == 0 {
 		return false
 	}
-
+	data := d.buf[:]
 	// read up, down, left and right proximity data from FIFO
 	var dataSets [32][4]uint8
 	for i := uint8(0); i < availableDataSets; i++ {
@@ -360,59 +411,72 @@ func (d *Device) configureDevice(cfg Configuration) {
 	}
 }
 
-func (d *Device) enable(cfg enableConfig) {
+func (d *Device) enable(cfg encfg) error {
-	var gen, pien, aien, wen, pen, aen, pon uint8
+	d.txNew()
-
+	cfg.write7bits(d.buf[:7])
-	if cfg.GEN {
+	d.txWrite(APDS9960_ENABLE_REG, d.buf[:7])
-		gen = 1
+	err := d.txErr()
-	}
+	if err == nil && cfg&enPON != 0 {
-	if cfg.PIEN {
-		pien = 1
-	}
-	if cfg.AIEN {
-		aien = 1
-	}
-	if cfg.WEN {
-		wen = 1
-	}
-	if cfg.PEN {
-		pen = 1
-	}
-	if cfg.AEN {
-		aen = 1
-	}
-	if cfg.PON {
-		pon = 1
-	}
-
-	data := []byte{gen<<6 | pien<<5 | aien<<4 | wen<<3 | pen<<2 | aen<<1 | pon}
-	legacy.WriteRegister(d.bus, d.Address, APDS9960_ENABLE_REG, data)
-
-	if cfg.PON {
 		time.Sleep(time.Millisecond * 10)
 	}
+	return err
 }
 
-func (d *Device) readStatus(param string) bool {
+func (d *Device) txErr() error { return d._txerr }
-	data := []byte{0}
-	legacy.ReadRegister(d.bus, d.Address, APDS9960_STATUS_REG, data)
 
-	switch param {
+func (d *Device) txNew() { d._txerr = nil }
-	case "CPSAT":
+
-		return data[0]>>7&0x01 == 1
+func (d *Device) txRead8(addr uint8) uint8 {
-	case "PGSAT":
+	if d._txerr != nil {
-		return data[0]>>6&0x01 == 1
+		return 0
-	case "PINT":
-		return data[0]>>5&0x01 == 1
-	case "AINT":
-		return data[0]>>4&0x01 == 1
-	case "PVALID":
-		return data[0]>>1&0x01 == 1
-	case "AVALID":
-		return data[0]&0x01 == 1
-	default:
-		return false
 	}
+	d.buf[0] = addr
+	d._txerr = d.bus.Tx(uint16(d.Address), d.buf[:1], d.buf[1:2])
+	return d.buf[1]
+}
+func (d *Device) txWrite8(addr uint8, val uint8) {
+	if d._txerr != nil {
+		return
+	}
+	d.buf[0] = addr
+	d.buf[1] = val
+	d._txerr = d.bus.Tx(uint16(d.Address), d.buf[:2], nil)
+}
+
+func (d *Device) txWrite(addr uint8, data []byte) {
+	if d._txerr != nil {
+		return
+	} else if len(data) > len(d.buf)-1 {
+		panic("txWrite: data too long")
+	}
+	d.buf[0] = addr
+	copy(d.buf[1:], data)
+	d._txerr = d.bus.Tx(uint16(d.Address), d.buf[:len(data)+1], nil)
+}
+
+type status uint8
+
+const (
+	statusAVALID status = 1 << iota
+	statusPVALID
+	_
+	_
+	statusAINT
+	statusPINT
+	statusPGSAT
+	statusCPSAT
+)
+
+func (s status) CPSAT() bool  { return s&statusCPSAT != 0 }
+func (s status) PGSAT() bool  { return s&statusPGSAT != 0 }
+func (s status) PINT() bool   { return s&statusPINT != 0 }
+func (s status) AINT() bool   { return s&statusAINT != 0 }
+func (s status) PVALID() bool { return s&statusPVALID != 0 }
+func (s status) AVALID() bool { return s&statusAVALID != 0 }
+
+func (d *Device) ReadStatus() (status, error) {
+	d.txNew()
+	return status(d.txRead8(APDS9960_STATUS_REG)), d.txErr()
 }
 
 func getPulseLength(l uint8) uint8 {