I was so happy with recent Example refactors, did it for all packages

This creates an example_test.go for each package with at least one
Example, and move all examples in it. Make the example_test.go file live
into a separate package 'foo_test' so it can call host.Init() and thus
can be copied as-is.

devices/apa102/apa102_test.go

@@ -11,12 +11,10 @@ import (
 	"image"
 	"image/color"
 	"io/ioutil"
-	"log"
 	"testing"
 
 	"periph.io/x/periph/conn/conntest"
 	"periph.io/x/periph/conn/spi"
-	"periph.io/x/periph/conn/spi/spireg"
 	"periph.io/x/periph/conn/spi/spitest"
 )
 
@@ -579,27 +577,6 @@ func TestInit(t *testing.T) {
 
 //
 
-func Example() {
-	s, err := spireg.Open("")
-	if err != nil {
-		log.Fatalf("failed to open SPI: %v", err)
-	}
-	defer s.Close()
-	// Opens a strip of 150 lights are 50% intensity with color temperature at
-	// 5000 Kelvin.
-	dev, err := New(s, 150, 127, 5000)
-	if err != nil {
-		log.Fatalf("failed to open apa102: %v", err)
-	}
-	img := image.NewNRGBA(image.Rect(0, 0, dev.Bounds().Dy(), 1))
-	for x := 0; x < img.Rect.Max.X; x++ {
-		img.SetNRGBA(x, 0, color.NRGBA{uint8(x), uint8(255 - x), 0, 255})
-	}
-	dev.Draw(dev.Bounds(), img, image.Point{})
-}
-
-//
-
 func BenchmarkWriteWhite(b *testing.B) {
 	pixels := make([]byte, 150*3)
 	for i := range pixels {

devices/apa102/example_test.go

@@ -0,0 +1,41 @@
+// Copyright 2018 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package apa102_test
+
+import (
+	"image"
+	"image/color"
+	"log"
+
+	"periph.io/x/periph/conn/spi/spireg"
+	"periph.io/x/periph/devices/apa102"
+	"periph.io/x/periph/host"
+)
+
+func Example() {
+	// Make sure periph is initialized.
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Use spireg SPI port registry to find the first available SPI bus.
+	p, err := spireg.Open("")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer p.Close()
+
+	// Opens a strip of 150 lights are 50% intensity with color temperature at
+	// 5000 Kelvin.
+	dev, err := apa102.New(p, 150, 127, 5000)
+	if err != nil {
+		log.Fatalf("failed to open apa102: %v", err)
+	}
+	img := image.NewNRGBA(image.Rect(0, 0, dev.Bounds().Dy(), 1))
+	for x := 0; x < img.Rect.Max.X; x++ {
+		img.SetNRGBA(x, 0, color.NRGBA{uint8(x), uint8(255 - x), 0, 255})
+	}
+	dev.Draw(dev.Bounds(), img, image.Point{})
+}

devices/bmxx80/bmx280_test.go

@@ -6,7 +6,6 @@ package bmxx80
 
 import (
 	"errors"
-	"fmt"
 	"io/ioutil"
 	"log"
 	"os"
@@ -14,7 +13,6 @@ import (
 	"time"
 
 	"periph.io/x/periph/conn/conntest"
-	"periph.io/x/periph/conn/i2c/i2creg"
 	"periph.io/x/periph/conn/i2c/i2ctest"
 	"periph.io/x/periph/conn/spi"
 	"periph.io/x/periph/conn/spi/spitest"
@@ -729,23 +727,6 @@ func TestCalibration280_limits_419430400(t *testing.T) {
 
 //
 
-func Example() {
-	bus, err := i2creg.Open("")
-	if err != nil {
-		log.Fatalf("failed to open I²C: %v", err)
-	}
-	defer bus.Close()
-	dev, err := NewI2C(bus, 0x76, nil)
-	if err != nil {
-		log.Fatalf("failed to initialize bme280: %v", err)
-	}
-	env := devices.Environment{}
-	if err := dev.Sense(&env); err != nil {
-		log.Fatal(err)
-	}
-	fmt.Printf("%8s %10s %9s\n", env.Temperature, env.Pressure, env.Humidity)
-}
-
 func TestOversampling(t *testing.T) {
 	data := []struct {
 		o Oversampling

devices/bmxx80/example_test.go

@@ -0,0 +1,38 @@
+// Copyright 2018 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package bmxx80_test
+
+import (
+	"fmt"
+	"log"
+
+	"periph.io/x/periph/conn/i2c/i2creg"
+	"periph.io/x/periph/devices"
+	"periph.io/x/periph/devices/bmxx80"
+	"periph.io/x/periph/host"
+)
+
+func Example() {
+	// Make sure periph is initialized.
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Use i2creg I²C bus registry to find the first available I²C bus.
+	b, err := i2creg.Open("")
+	if err != nil {
+		log.Fatalf("failed to open I²C: %v", err)
+	}
+	defer b.Close()
+	d, err := bmxx80.NewI2C(b, 0x76, nil)
+	if err != nil {
+		log.Fatalf("failed to initialize bme280: %v", err)
+	}
+	e := devices.Environment{}
+	if err := d.Sense(&e); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%8s %10s %9s\n", e.Temperature, e.Pressure, e.Humidity)
+}

devices/ds248x/ds248x_test.go

@@ -5,42 +5,12 @@
 package ds248x
 
 import (
-	"fmt"
-	"log"
 	"testing"
 	"time"
 
-	"periph.io/x/periph/conn/i2c/i2creg"
 	"periph.io/x/periph/conn/i2c/i2ctest"
 )
 
-func Example() {
-	// Open the I²C bus to which the DS248x is connected.
-	i2cBus, err := i2creg.Open("")
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer i2cBus.Close()
-
-	// Open the DS248x to get a 1-wire bus.
-	owBus, err := New(i2cBus, nil)
-	if err != nil {
-		log.Fatal(err)
-	}
-	// Search devices on the bus
-	devices, err := owBus.Search(false)
-	if err != nil {
-		log.Fatal(err)
-	}
-	fmt.Printf("Found %d 1-wire devices: ", len(devices))
-	for _, d := range devices {
-		fmt.Printf(" %#16x", uint64(d))
-	}
-	fmt.Print("\n")
-}
-
-//
-
 func TestNew(t *testing.T) {
 	bus := i2ctest.Playback{
 		Ops: []i2ctest.IO{

devices/ds248x/example_test.go

@@ -0,0 +1,44 @@
+// Copyright 2018 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package ds248x_test
+
+import (
+	"fmt"
+	"log"
+
+	"periph.io/x/periph/conn/i2c/i2creg"
+	"periph.io/x/periph/devices/ds248x"
+	"periph.io/x/periph/host"
+)
+
+func Example() {
+	// Make sure periph is initialized.
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Use i2creg I²C bus registry to find the first available I²C bus.
+	b, err := i2creg.Open("")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer b.Close()
+
+	// Open the DS248x to get a 1-wire bus.
+	ob, err := ds248x.New(b, nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+	// Search devices on the bus
+	devices, err := ob.Search(false)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("Found %d 1-wire devices: ", len(devices))
+	for _, d := range devices {
+		fmt.Printf(" %#16x", uint64(d))
+	}
+	fmt.Print("\n")
+}

devices/ssd1306/example_test.go

@@ -0,0 +1,54 @@
+// Copyright 2018 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package ssd1306_test
+
+import (
+	"image"
+	"log"
+
+	"periph.io/x/periph/conn/i2c/i2creg"
+	"periph.io/x/periph/devices/ssd1306"
+	"periph.io/x/periph/devices/ssd1306/image1bit"
+	"periph.io/x/periph/host"
+)
+
+func Example() {
+	// Make sure periph is initialized.
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Use i2creg I²C bus registry to find the first available I²C bus.
+	b, err := i2creg.Open("")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer b.Close()
+
+	dev, err := ssd1306.NewI2C(b, 128, 64, false)
+	if err != nil {
+		log.Fatalf("failed to initialize ssd1306: %v", err)
+	}
+
+	// Draw on it.
+	img := image1bit.NewVerticalLSB(dev.Bounds())
+	// Note: this code is commented out so periph does not depend on:
+	//    "golang.org/x/image/font"
+	//    "golang.org/x/image/font/basicfont"
+	//    "golang.org/x/image/math/fixed"
+	//
+	// f := basicfont.Face7x13
+	// drawer := font.Drawer{
+	// 	Dst:  img,
+	// 	Src:  &image.Uniform{image1bit.On},
+	// 	Face: f,
+	// 	Dot:  fixed.P(0, img.Bounds().Dy()-1-f.Descent),
+	// }
+	// drawer.DrawString("Hello from periph!")
+	dev.Draw(dev.Bounds(), img, image.Point{})
+	if err := dev.Err(); err != nil {
+		log.Fatal(err)
+	}
+}

devices/ssd1306/ssd1306_test.go

@@ -8,53 +8,17 @@ import (
 	"errors"
 	"image"
 	"image/color"
-	"log"
 	"testing"
 
 	"periph.io/x/periph/conn/conntest"
 	"periph.io/x/periph/conn/gpio"
 	"periph.io/x/periph/conn/gpio/gpiotest"
-	"periph.io/x/periph/conn/i2c/i2creg"
 	"periph.io/x/periph/conn/i2c/i2ctest"
 	"periph.io/x/periph/conn/spi"
 	"periph.io/x/periph/conn/spi/spitest"
 	"periph.io/x/periph/devices/ssd1306/image1bit"
 )
 
-func Example() {
-	bus, err := i2creg.Open("")
-	if err != nil {
-		log.Fatalf("failed to open I²C: %v", err)
-	}
-	defer bus.Close()
-	dev, err := NewI2C(bus, 128, 64, false)
-	if err != nil {
-		log.Fatalf("failed to initialize ssd1306: %v", err)
-	}
-
-	// Draw on it.
-	img := image1bit.NewVerticalLSB(dev.Bounds())
-	// Note: this code is commented out so periph does not depend on:
-	//    "golang.org/x/image/font"
-	//    "golang.org/x/image/font/basicfont"
-	//    "golang.org/x/image/math/fixed"
-	//
-	// f := basicfont.Face7x13
-	// drawer := font.Drawer{
-	// 	Dst:  img,
-	// 	Src:  &image.Uniform{image1bit.On},
-	// 	Face: f,
-	// 	Dot:  fixed.P(0, img.Bounds().Dy()-1-f.Descent),
-	// }
-	// drawer.DrawString("Hello from periph!")
-	dev.Draw(dev.Bounds(), img, image.Point{})
-	if err := dev.Err(); err != nil {
-		log.Fatal(err)
-	}
-}
-
-//
-
 func TestNewI2C_fail(t *testing.T) {
 	bus := i2ctest.Playback{DontPanic: true}
 	if d, err := NewI2C(&bus, 0, 64, false); d != nil || err == nil {

devices/tm1637/example_test.go

@@ -0,0 +1,36 @@
+// Copyright 2018 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package tm1637_test
+
+import (
+	"log"
+
+	"periph.io/x/periph/conn/gpio/gpioreg"
+	"periph.io/x/periph/devices/tm1637"
+	"periph.io/x/periph/host"
+)
+
+func Example() {
+	// Make sure periph is initialized.
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	clk := gpioreg.ByName("GPIO6")
+	data := gpioreg.ByName("GPIO12")
+	if clk == nil || data == nil {
+		log.Fatal("Failed to find pins")
+	}
+	dev, err := tm1637.New(clk, data)
+	if err != nil {
+		log.Fatalf("failed to initialize tm1637: %v", err)
+	}
+	if err := dev.SetBrightness(tm1637.Brightness10); err != nil {
+		log.Fatalf("failed to set brightness on tm1637: %v", err)
+	}
+	if _, err := dev.Write(tm1637.Clock(12, 00, true)); err != nil {
+		log.Fatalf("failed to write to tm1637: %v", err)
+	}
+}

devices/tm1637/tm1637_test.go

@@ -12,29 +12,9 @@ import (
 	"time"
 
 	"periph.io/x/periph/conn/gpio"
-	"periph.io/x/periph/conn/gpio/gpioreg"
 	"periph.io/x/periph/conn/gpio/gpiotest"
-	"periph.io/x/periph/host"
 )
 
-func Example() {
-	if _, err := host.Init(); err != nil {
-		log.Fatalf("failed to initialize periph: %v", err)
-	}
-	dev, err := New(gpioreg.ByName("GPIO6"), gpioreg.ByName("GPIO12"))
-	if err != nil {
-		log.Fatalf("failed to initialize tm1637: %v", err)
-	}
-	if err := dev.SetBrightness(Brightness10); err != nil {
-		log.Fatalf("failed to set brightness on tm1637: %v", err)
-	}
-	if _, err := dev.Write(Clock(12, 00, true)); err != nil {
-		log.Fatalf("failed to write to tm1637: %v", err)
-	}
-}
-
-//
-
 func TestNew(t *testing.T) {
 	var clk, data gpiotest.Pin
 	dev, err := New(&clk, &data)