mfrc522: improvements to gain and wait (#297)

- Antenna Gain
- Terminating Wait if Halt received
- Renamed SetOperationtimeout to SetOperationTimeout

experimental/devices/mfrc522/mfrc522.go

@@ -11,6 +11,7 @@ package mfrc522
 
 import (
 	"fmt"
+	"sync"
 	"time"
 
 	"periph.io/x/periph/conn"
@@ -119,6 +120,8 @@ func NewSPI(spiPort spi.Port, resetPin gpio.PinOut, irqPin gpio.PinIn) (*Dev, er
 		operationTimeout: 30 * time.Second,
 		irqPin:           irqPin,
 		resetPin:         resetPin,
+		antennaGain:      4,
+		stop:             make(chan struct{}, 1),
 	}
 	if err := dev.Init(); err != nil {
 		return nil, err
@@ -132,6 +135,13 @@ type Dev struct {
 	irqPin           gpio.PinIn
 	operationTimeout time.Duration
 	spiDev           spi.Conn
+	stop             chan struct{}
+
+	aMu         sync.Mutex
+	antennaGain int
+
+	mu        sync.Mutex
+	isWaiting bool
 }
 
 // String implements conn.Resource.
@@ -144,16 +154,28 @@ func (r *Dev) String() string {
 //
 // It soft-stops the chip - PowerDown bit set, command IDLE
 func (r *Dev) Halt() error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if r.isWaiting {
+		select {
+		case <-r.stop:
+		default:
+		}
+
+		r.stop <- struct{}{}
+	}
+
 	return r.devWrite(commands.CommandReg, 16)
 }
 
-// SetOperationtimeout updates the device timeout for card operations.
+// SetOperationTimeout updates the device timeout for card operations.
 //
 // Effectively that sets the maximum time the RFID device will wait for IRQ
 // from the proximity card detection.
 //
 //	timeout the duration to wait for IRQ strobe.
-func (r *Dev) SetOperationtimeout(timeout time.Duration) {
+func (r *Dev) SetOperationTimeout(timeout time.Duration) {
 	r.operationTimeout = timeout
 }
 
@@ -165,6 +187,15 @@ func (r *Dev) Init() error {
 	if err := r.writeCommandSequence(sequenceCommands.init); err != nil {
 		return err
 	}
+
+	r.aMu.Lock()
+	gain := byte(r.antennaGain)<<4
+	r.aMu.Unlock()
+
+	if err := r.devWrite(int(commands.RFCfgReg), gain); err != nil {
+		return err
+	}
+
 	return r.SetAntenna(true)
 }
 
@@ -188,6 +219,18 @@ func (r *Dev) SetAntenna(state bool) error {
 	return r.clearBitmask(commands.TxControlReg, 0x03)
 }
 
+// SetAntennaGain configures antenna signal strength.
+//
+//	gain - signal strength from 0 to 7.
+func (r *Dev) SetAntennaGain(gain int) {
+	r.aMu.Lock()
+	defer r.aMu.Unlock()
+
+	if 0 <= gain && gain <= 7 {
+		r.antennaGain = gain
+	}
+}
+
 // CardWrite the low-level interface to write some raw commands to the card.
 //
 // 	command - the command register
@@ -321,12 +364,35 @@ func (r *Dev) Request() (int, error) {
 
 // Wait wait for IRQ to strobe on the IRQ pin when the card is detected.
 func (r *Dev) Wait() error {
+	r.mu.Lock()
+	waitCancelled := false
+	if r.isWaiting {
+		r.mu.Unlock()
+		return wrapf("concurrent access is forbidden")
+	}
+
+	r.isWaiting = true
+	r.mu.Unlock()
+
 	irqChannel := make(chan bool)
+
 	go func() {
-		irqChannel <- r.irqPin.WaitForEdge(r.operationTimeout)
+		result := r.irqPin.WaitForEdge(r.operationTimeout)
+		r.mu.Lock()
+		defer r.mu.Unlock()
+		if waitCancelled {
+			return
+		}
+
+		irqChannel <- result
 	}()
 
 	defer func() {
+		r.mu.Lock()
+		r.isWaiting = false
+		waitCancelled = true
+		r.mu.Unlock()
+
 		close(irqChannel)
 	}()
 
@@ -342,6 +408,8 @@ func (r *Dev) Wait() error {
 			return err
 		}
 		select {
+		case <-r.stop:
+			return wrapf("halt")
 		case irqResult := <-irqChannel:
 			if !irqResult {
 				return wrapf("timeout waitinf for IRQ edge: %v", r.operationTimeout)