apa102: adding initial support for APA102 LEDs, thanks to code sample…

… from @rakyll

Signed-off-by: deadprogram <[email protected]>

drivers/spi/apa102.go

@@ -0,0 +1,92 @@
+package spi
+
+import (
+	"image/color"
+
+	"gobot.io/x/gobot"
+)
+
+// APA102Driver is a driver for the APA102 programmable RGB LEDs
+type APA102Driver struct {
+	name       string
+	connector  Connector
+	connection Connection
+
+	vals []color.RGBA
+}
+
+// NewAPA102Driver creates a new Gobot Driver for APA102 RGB LEDs.
+//
+// Params:
+//      a *Adaptor - the Adaptor to use with this Driver
+//		count int - how many LEDs are in the array controlled by this driver
+//
+func NewAPA102Driver(a Connector, count int) *APA102Driver {
+	d := &APA102Driver{
+		name:      gobot.DefaultName("APA102"),
+		connector: a,
+		vals:      make([]color.RGBA, count),
+	}
+	return d
+}
+
+// Name returns the name of the device.
+func (d *APA102Driver) Name() string { return d.name }
+
+// SetName sets the name of the device.
+func (d *APA102Driver) SetName(n string) { d.name = n }
+
+// Connection returns the Connection of the device.
+func (d *APA102Driver) Connection() gobot.Connection { return d.connection.(gobot.Connection) }
+
+// Start initializes the driver.
+func (d *APA102Driver) Start() (err error) {
+	bus := d.connector.GetSpiDefaultBus()
+	mode := d.connector.GetSpiDefaultMode()
+	maxSpeed := d.connector.GetSpiDefaultMaxSpeed()
+	d.connection, err = d.connector.GetSpiConnection(bus, mode, maxSpeed)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Halt stops the driver.
+func (d *APA102Driver) Halt() (err error) {
+	d.connection.Close()
+	return
+}
+
+// SetRGBA sets the ith LED's color to the given RGBA value.
+// A subsequent call to Draw is required to transmit values
+// to the LED strip.
+func (d *APA102Driver) SetRGBA(i int, v color.RGBA) {
+	d.vals[i] = v
+}
+
+// Draw displays the RGBA values set on the actual LED strip.
+func (d *APA102Driver) Draw() error {
+	// TODO(jbd): dotstar allows other RGBA alignments, support those layouts.
+	n := len(d.vals)
+
+	tx := make([]byte, 4*(n+1)+(n/2+1))
+	tx[0] = 0x00
+	tx[1] = 0x00
+	tx[2] = 0x00
+	tx[3] = 0x00
+
+	for i, c := range d.vals {
+		j := (i + 1) * 4
+		tx[j] = 0xe0 + byte(c.R)
+		tx[j+1] = byte(c.B)
+		tx[j+2] = byte(c.G)
+		tx[j+3] = byte(c.R)
+	}
+
+	// end frame with at least n/2 0xff vals
+	for i := (n + 1) * 4; i < len(tx); i++ {
+		tx[i] = 0xff
+	}
+
+	return d.connection.Tx(tx, nil)
+}

drivers/spi/apa102_test.go

@@ -0,0 +1,39 @@
+package spi
+
+import (
+	"image/color"
+	"testing"
+
+	"gobot.io/x/gobot"
+	"gobot.io/x/gobot/gobottest"
+)
+
+var _ gobot.Driver = (*APA102Driver)(nil)
+
+func initTestDriver() *APA102Driver {
+	d := NewAPA102Driver(&TestConnector{}, 10)
+	return d
+}
+
+func TestDriverStart(t *testing.T) {
+	d := initTestDriver()
+	gobottest.Assert(t, d.Start(), nil)
+}
+
+func TestDriverHalt(t *testing.T) {
+	d := initTestDriver()
+	d.Start()
+	gobottest.Assert(t, d.Halt(), nil)
+}
+
+func TestDriverLEDs(t *testing.T) {
+	d := initTestDriver()
+	d.Start()
+
+	d.SetRGBA(0, color.RGBA{255, 255, 255, 0})
+	d.SetRGBA(1, color.RGBA{255, 255, 255, 0})
+	d.SetRGBA(2, color.RGBA{255, 255, 255, 0})
+	d.SetRGBA(3, color.RGBA{255, 255, 255, 0})
+
+	gobottest.Assert(t, d.Draw(), nil)
+}

drivers/spi/spi_test.go

@@ -0,0 +1,61 @@
+package spi
+
+import (
+	"time"
+
+	xspi "golang.org/x/exp/io/spi"
+)
+
+type TestConnector struct{}
+
+func (ctr *TestConnector) GetSpiConnection(busNum, mode int, maxSpeed int64) (device Connection, err error) {
+	return NewConnection(&TestSpiDevice{}), nil
+}
+
+func (ctr *TestConnector) GetSpiDefaultBus() int {
+	return 0
+}
+
+func (ctr *TestConnector) GetSpiDefaultMode() int {
+	return 0
+}
+
+func (ctr *TestConnector) GetSpiDefaultMaxSpeed() int64 {
+	return 0
+}
+
+type TestSpiDevice struct {
+	bus SPIDevice
+}
+
+func (c *TestSpiDevice) Close() error {
+	return nil
+}
+
+func (c *TestSpiDevice) SetBitOrder(o xspi.Order) error {
+	return nil
+}
+
+func (c *TestSpiDevice) SetBitsPerWord(bits int) error {
+	return nil
+}
+
+func (c *TestSpiDevice) SetCSChange(leaveEnabled bool) error {
+	return nil
+}
+
+func (c *TestSpiDevice) SetDelay(t time.Duration) error {
+	return nil
+}
+
+func (c *TestSpiDevice) SetMaxSpeed(speed int) error {
+	return nil
+}
+
+func (c *TestSpiDevice) SetMode(mode xspi.Mode) error {
+	return nil
+}
+
+func (c *TestSpiDevice) Tx(w, r []byte) error {
+	return nil
+}