ep0099: optionally read device state on new

ep0099/ep0099.go

@@ -25,7 +25,15 @@
 	state [4]State
 }
 
+type Opts struct {
+	ReadStates bool // ReadStates from the device on startup instead of resetting the device.
+}
+
 func New(bus i2c.Bus, address uint16) (*Dev, error) {
+	return NewWithOpts(bus, address, nil)
+}
+
+func NewWithOpts(bus i2c.Bus, address uint16, opts *Opts) (*Dev, error) {
 	if err := isValidAddress(address); err != nil {
 		return nil, err
 	}
@@ -34,15 +42,20 @@
 		i2c: i2c.Dev{Bus: bus, Addr: address},
 	}
 
-	if err := d.reset(); err != nil {
+	bootFn := d.Reset
+	if opts != nil && opts.ReadStates {
+		bootFn = d.ReadStates
+	}
+
+	if err := bootFn(); err != nil {
 		return nil, err
 	}
 
 	return d, nil
 }
 
 func (d *Dev) Halt() error {
-	return d.reset()
+	return d.Reset()
 }
 
 func (d *Dev) On(channel uint8) error {
@@ -72,6 +85,20 @@
 	return d.state[channel-1], nil
 }
 
+func (d *Dev) ReadStates() error {
+	for i, channel := range d.AvailableChannels() {
+		read := make([]byte, 1)
+
+		if err := d.i2c.Tx([]byte{channel}, read); err != nil {
+			return err
+		}
+
+		d.state[i] = State(read[0])
+	}
+
+	return nil
+}
+
 func (d *Dev) AvailableChannels() []uint8 {
 	return []uint8{0x01, 0x02, 0x03, 0x04}
 }
@@ -83,7 +110,7 @@
 	return "on"
 }
 
-func (d *Dev) reset() error {
+func (d *Dev) Reset() error {
 	for _, channel := range d.AvailableChannels() {
 		err := d.Off(channel)
 		if err != nil {

ep0099/ep0099_test.go

@@ -12,6 +12,7 @@ import (
 	"testing"
 
 	"periph.io/x/conn/v3/i2c/i2ctest"
+	"periph.io/x/conn/v3/physic"
 )
 
 const (
@@ -90,6 +91,22 @@ func TestOff(t *testing.T) {
 	checkChannelState(t, dev, 4, StateOff)
 }
 
+func TestReadState(t *testing.T) {
+	bus := initTestBus()
+	bus.Bus = &testBus{states: [4]State{StateOff, StateOn, StateOff, StateOn}}
+
+	dev, err := NewWithOpts(bus, testDefaultValidAddress, &Opts{ReadStates: true})
+
+	if err != nil {
+		t.Fatal("Failed to create dev with ReadStates, got ", err)
+	}
+
+	checkChannelState(t, dev, 1, StateOff)
+	checkChannelState(t, dev, 2, StateOn)
+	checkChannelState(t, dev, 3, StateOff)
+	checkChannelState(t, dev, 4, StateOn)
+}
+
 func TestReturnErrorForInvalidChannel(t *testing.T) {
 	bus := initTestBus()
 	dev, _ := New(bus, testDefaultValidAddress)
@@ -153,3 +170,27 @@ func checkDevReset(t *testing.T, dev *Dev, bus *i2ctest.Record) {
 	checkBusHasWrite(t, bus, []byte{4, byte(StateOff)})
 	checkChannelState(t, dev, 4, StateOff)
 }
+
+type testBus struct {
+	states [4]State
+}
+
+func (b *testBus) String() string {
+	return "ep0099 test i2c bus"
+}
+
+func (b *testBus) Tx(addr uint16, w, r []byte) error {
+	if len(w) == 1 && len(r) == 1 {
+		if w[0] < 1 || w[0] > 4 {
+			return errors.New("Invalid port")
+		}
+
+		r[0] = byte(b.states[w[0]-1])
+	}
+
+	return nil
+}
+
+func (b *testBus) SetSpeed(f physic.Frequency) error {
+	return nil
+}