add i2c implementation

firmata/client.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 
 	"periph.io/x/conn/v3/gpio"
+	"periph.io/x/conn/v3/i2c"
 	"periph.io/x/conn/v3/onewire"
 	"periph.io/x/conn/v3/pin"
 )
@@ -38,16 +39,18 @@ type ClientI interface {
 	SetSamplingInterval(uint16) error
 	SetDigitalPinValue(p uint8, value gpio.Level) error
 	SendAnalogMappingQuery() (chan AnalogMappingResponse, error)
-	SetI2CMessageChannel(address uint8, ch chan I2CPacket)
-	WriteI2CData(address uint8, restart bool, data []uint8) error
-	ReadI2CData(address uint8, restart bool, len uint16) error
-	ReadI2CRegister(address uint8, restart bool, register uint8, len uint16) error
-	SendI2CConfig(delayMicroseconds uint8) error
 	AnalogPinToDigitalPin(p uint8) (uint8, error)
 	SetAnalogIOMessageListener(p uint8, ch chan uint16) (release func(), err error)
 	SetDigitalIOMessageListener(p uint8, ch chan gpio.Level) (release func(), err error)
 	SendAnalogIOMessage(uint8, uint16) error
 
+	OpenI2CBus() (i2c.Bus, error)
+	SetI2CAddressListener(addr uint8, ch chan I2CPacket) (release func(), err error)
+	WriteI2CData(address uint8, restart bool, data []uint8) error
+	ReadI2CData(address uint8, restart bool, len uint16) error
+	ReadI2CRegister(address uint8, restart bool, register uint8, len uint16) error
+	SendI2CConfig(delayMicroseconds uint8) error
+
 	OpenOneWireBus(p uint8) (bus onewire.BusCloser, err error)
 	SetOneWireListener(uint8, chan []byte) (release func(), err error)
 
@@ -61,7 +64,9 @@ type Client struct {
 	board                 io.ReadWriteCloser
 	responseChannels      map[SysExCmd][]chan []byte
 	sysExListenerChannels map[SysExCmd]chan []byte
-	i2cListeners          map[uint8]chan I2CPacket
+
+	i2cListeners map[uint8]chan I2CPacket
+	i2cMU        sync.Mutex
 
 	onewireListeners map[uint8]chan []byte
 	onewireMU        sync.Mutex
@@ -587,13 +592,25 @@ func (c *Client) SendI2CConfig(delayMicroseconds uint8) error {
 	return nil
 }
 
+func (c *Client) releaseI2CAddressListener(addr uint8) {
+	c.i2cMU.Lock()
+	defer c.i2cMU.Unlock()
+
+	delete(c.i2cListeners, addr)
+}
+
 // This function only supports 7-bit I2C addresses
-func (c *Client) SetI2CMessageChannel(address uint8, ch chan I2CPacket) {
-	if c.i2cListeners[address] != nil {
-		close(c.i2cListeners[address])
+func (c *Client) SetI2CAddressListener(addr uint8, ch chan I2CPacket) (release func(), err error) {
+	c.i2cMU.Lock()
+	defer c.i2cMU.Unlock()
+
+	if c.i2cListeners[addr] != nil {
+		return nil, ErrI2CAddressListenerNotReleased
 	}
 
-	c.i2cListeners[address] = ch
+	c.i2cListeners[addr] = ch
+
+	return func() { c.releaseI2CAddressListener(addr) }, nil
 }
 
 func (c *Client) releaseAnalogIOMessageListener(p uint8) {
@@ -695,3 +712,7 @@ func (c *Client) GetPinName(p uint8) string {
 func (c *Client) GetPinFunctions(p uint8) []pin.Func {
 	return c.cr.SupportedPinModes[int(p)]
 }
+
+func (c *Client) OpenI2CBus() (i2c.Bus, error) {
+	return newI2CBus(c)
+}

firmata/errors.go

@@ -21,4 +21,5 @@ var (
 	ErrAnalogIOMessagePinOutOfRange       = errors.New("analog io message pin number cannot exceed 0xF")
 	ErrDigitalIOMessagePinOutOfRange      = errors.New("digital io message port number cannot exceed 0xF")
 	ErrPinListenerNotReleased             = errors.New("pin listener is already set for pin")
+	ErrI2CAddressListenerNotReleased      = errors.New("address listener is already set")
 )

firmata/i2c.go

@@ -1,33 +1,86 @@
 package firmata
 
 import (
-	"periph.io/x/conn/v3/gpio"
+	"errors"
+	"fmt"
+	"math"
+	"sync"
+
 	"periph.io/x/conn/v3/physic"
 )
 
+var (
+	Err10BitAddressingNotSupported = errors.New("10-bit addressing not supported")
+)
+
 type I2CBus struct {
+	c  ClientI
+	mu sync.Mutex
 }
 
-func (i *I2CBus) SCL() gpio.PinIO {
-	panic("implement me")
-}
+func newI2CBus(c ClientI) (*I2CBus, error) {
+	b := &I2CBus{
+		c: c,
+	}
 
-func (i *I2CBus) SDA() gpio.PinIO {
-	panic("implement me")
+	err := c.SendI2CConfig(0)
+	if err != nil {
+		return nil, err
+	}
+
+	return b, nil
 }
 
-func (i *I2CBus) Close() error {
+func (b *I2CBus) Close() error {
 	panic("implement me")
 }
 
-func (i *I2CBus) String() string {
+func (b *I2CBus) String() string {
 	panic("implement me")
 }
 
-func (i *I2CBus) Tx(addr uint16, w, r []byte) error {
-	panic("implement me")
+func (b *I2CBus) Tx(addr uint16, w, r []byte) error {
+	if addr >= 0b11111111 {
+		return fmt.Errorf("%w: 0x%04X", Err10BitAddressingNotSupported, addr)
+	}
+
+	if len(r) > math.MaxUint16 {
+		return fmt.Errorf("%w: cannot reach more than %d bytes", ErrValueOutOfRange, math.MaxUint16)
+	}
+
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	ch := make(chan I2CPacket)
+	defer close(ch)
+
+	address := uint8(addr)
+
+	release, err := b.c.SetI2CAddressListener(address, ch)
+	if err != nil {
+		return err
+	}
+	defer release()
+
+	if len(w) > 0 {
+		if err := b.c.WriteI2CData(address, false, w); err != nil {
+			return err
+		}
+	}
+
+	if len(r) > 0 {
+		if err := b.c.ReadI2CData(address, false, uint16(len(r))); err != nil {
+			return err
+		}
+
+		pck := <-ch
+
+		copy(r, pck.Data)
+	}
+
+	return nil
 }
 
-func (i *I2CBus) SetSpeed(f physic.Frequency) error {
-	panic("implement me")
+func (b *I2CBus) SetSpeed(f physic.Frequency) error {
+	return fmt.Errorf("%w: firmata does not support setting bus frequency", ErrUnsupportedFeature)
 }