mcp23017: implement pin toggling

Also add an example for using multiple devices.

mcp23017/device.go

@@ -154,6 +154,15 @@ func (d *Device) SetPins(pins, mask Pins) error {
 	return nil
 }
 
+// TogglePins inverts the values on all pins for
+// which mask is high.
+func (d *Device) TogglePins(mask Pins) error {
+	if mask == 0 {
+		return nil
+	}
+	return d.SetPins(^d.pins, mask)
+}
+
 // Pin returns a Pin representing the given pin number (from 0 to 15).
 // Pin numbers from 0 to 7 represent port A pins 0 to 7.
 // Pin numbers from 8 to 15 represent port B pins 0 to 7.
@@ -295,6 +304,11 @@ func (p Pin) Low() error {
 	return p.Set(false)
 }
 
+// Toggle inverts the value output on the pin.
+func (p Pin) Toggle() error {
+	return p.dev.TogglePins(p.mask)
+}
+
 // Get returns the current value of the given pin.
 func (p Pin) Get() (bool, error) {
 	// TODO this reads 2 registers when we could read just one.
@@ -357,6 +371,11 @@ func (p *Pins) Low(pin int) {
 	*p &^= pinMask(pin)
 }
 
+// Toggle inverts the value of the given pin.
+func (p *Pins) Toggle(pin int) {
+	*p ^= pinMask(pin)
+}
+
 func pinMask(pin int) Pins {
 	return 1 << pin
 }

mcp23017/device_test.go

@@ -50,6 +50,25 @@ func TestSetPins(t *testing.T) {
 	c.Assert(pins, qt.Equals, Pins(0b01010000_00011010))
 }
 
+func TestTogglePins(t *testing.T) {
+	c := qt.New(t)
+	bus := newBus(c)
+	fdev := bus.addDevice(0x20)
+	fdev.Registers[rGPIO] = 0b00001111
+	fdev.Registers[rGPIO|portB] = 0b11110000
+	dev, err := NewI2C(bus, 0x20)
+	c.Assert(err, qt.IsNil)
+	pins, err := dev.GetPins()
+	c.Assert(err, qt.IsNil)
+	c.Assert(pins, qt.Equals, Pins(0b11110000_00001111))
+
+	err = dev.TogglePins(0b10101010_01010101)
+	c.Assert(err, qt.IsNil)
+	pins, err = dev.GetPins()
+	c.Assert(err, qt.IsNil)
+	c.Assert(pins, qt.Equals, Pins(0b01011010_01011010))
+}
+
 func TestSetGetModes(t *testing.T) {
 	c := qt.New(t)
 	bus := newBus(c)
@@ -108,6 +127,24 @@ func TestPinSetGet(t *testing.T) {
 	c.Assert(fdev.Registers[rGPIO], qt.Equals, uint8(0))
 }
 
+func TestPinToggle(t *testing.T) {
+	c := qt.New(t)
+	bus := newBus(c)
+	fdev := bus.addDevice(0x20)
+	dev, err := NewI2C(bus, 0x20)
+	c.Assert(err, qt.IsNil)
+	pin := dev.Pin(1)
+	v, err := pin.Get()
+	c.Assert(err, qt.Equals, nil)
+	c.Assert(v, qt.Equals, false)
+	err = pin.Toggle()
+	c.Assert(err, qt.Equals, nil)
+	c.Assert(fdev.Registers[rGPIO], qt.Equals, uint8(0b10))
+	err = pin.Toggle()
+	c.Assert(err, qt.Equals, nil)
+	c.Assert(fdev.Registers[rGPIO], qt.Equals, uint8(0))
+}
+
 func TestPinMode(t *testing.T) {
 	c := qt.New(t)
 	bus := newBus(c)

mcp23017/multidevice.go

@@ -117,6 +117,22 @@ func (devs Devices) SetPins(pins, mask PinSlice) error {
 	return nil
 }
 
+// TogglePins inverts the values on all pins for
+// which mask is high.
+func (devs Devices) TogglePins(mask PinSlice) error {
+	defaultMask := mask.extra()
+	for i, dev := range devs {
+		devMask := defaultMask
+		if i < len(mask) {
+			devMask = mask[i]
+		}
+		if err := dev.TogglePins(devMask); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 // PinSlice represents an arbitrary nunber of pins, each element corresponding
 // to the pins for one device. The value of the highest numbered pin in the
 // slice is extended to all other pins beyond the end of the slice.
@@ -154,6 +170,11 @@ func (pins PinSlice) Low(pin int) {
 	pins[pin/PinCount].Low(pin % PinCount)
 }
 
+// Toggle inverts the value of the given pin.
+func (pins PinSlice) Toggle(pin int) {
+	pins[pin/PinCount].Toggle(pin % PinCount)
+}
+
 // Ensure checks that pins has enough space to store
 // at least length pins. If it does, it returns pins unchanged.
 // Otherwise, it returns pins with elements appended as needed,

mcp23017/multidevice_test.go

@@ -102,6 +102,26 @@ func TestDevicesSetPinsMask(t *testing.T) {
 	c.Assert(pins, qt.DeepEquals, PinSlice{0b01010011_10101101, 0b01010010_10101100})
 }
 
+func TestDevicesTogglePins(t *testing.T) {
+	c := qt.New(t)
+	bus := newBus(c)
+	bus.addDevice(0x20)
+	bus.addDevice(0x21)
+	devs, err := NewI2CDevices(bus, 0x20, 0x21)
+	c.Assert(err, qt.IsNil)
+
+	mask := make(PinSlice, 2)
+	mask.High(0)
+	mask.High(16)
+
+	err = devs.TogglePins(mask)
+	c.Assert(err, qt.IsNil)
+	pins := make(PinSlice, 2)
+	err = devs.GetPins(pins)
+	c.Assert(err, qt.IsNil)
+	c.Assert(pins, qt.DeepEquals, PinSlice{0b00000000_00000001, 0b00000000_00000001})
+}
+
 func TestDevicesSetGetModes(t *testing.T) {
 	c := qt.New(t)
 	bus := newBus(c)
@@ -163,4 +183,6 @@ func TestPinSlice(t *testing.T) {
 	c.Assert(pins.Get(16), qt.Equals, false)
 	pins.High(16)
 	c.Assert(pins.Get(16), qt.Equals, true)
+	pins.Toggle(16)
+	c.Assert(pins.Get(16), qt.Equals, false)
 }