From ae26e1d7f02b5702585ae8669a193f902ecd1a6f Mon Sep 17 00:00:00 2001
From: Ben Schwartz <benschw@gmail.com>
Date: Sun, 29 Mar 2015 09:02:10 -0500
Subject: [PATCH] adding stepper motor example

---
 samples/28bjy-48.go | 111 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 samples/28bjy-48.go

diff --git a/samples/28bjy-48.go b/samples/28bjy-48.go
new file mode 100644
index 0000000..1e61d2a
--- /dev/null
+++ b/samples/28bjy-48.go
@@ -0,0 +1,111 @@
+// +build ignore
+
+package main
+
+// Control a stepper motor (28BJY-48)
+//
+// Datasheet:
+// http://www.raspberrypi-spy.co.uk/wp-content/uploads/2012/07/Stepper-Motor-28BJY-48-Datasheet.pdf
+//
+// this is a port of Matt Hawkins' example impl from
+// http://www.raspberrypi-spy.co.uk/2012/07/stepper-motor-control-in-python/
+// (link privides additional instructions for wiring your pi)
+
+import (
+	"flag"
+	"fmt"
+	"github.com/kidoman/embd"
+	_ "github.com/kidoman/embd/host/rpi"
+	"os"
+	"os/signal"
+	"time"
+)
+
+func main() {
+	stepWait := flag.Int("step-delay", 10, "milliseconds between steps")
+	flag.Parse()
+
+	if err := embd.InitGPIO(); err != nil {
+		panic(err)
+	}
+	defer embd.CloseGPIO()
+
+	// Physical pins 11,15,16,18
+	// GPIO17,GPIO22,GPIO23,GPIO24
+	stepPinNums := []int{17, 22, 23, 24}
+
+	stepPins := make([]embd.DigitalPin, 4)
+
+	for i, pinNum := range stepPinNums {
+		pin, err := embd.NewDigitalPin(pinNum)
+		if err != nil {
+			panic(err)
+		}
+		defer pin.Close()
+		if err := pin.SetDirection(embd.Out); err != nil {
+			panic(err)
+		}
+		if err := pin.Write(embd.Low); err != nil {
+			panic(err)
+		}
+		defer func() {
+			if err := pin.SetDirection(embd.In); err != nil {
+				panic(err)
+			}
+		}()
+
+		stepPins[i] = pin
+	}
+
+	// Define advanced sequence
+	// as shown in manufacturers datasheet
+	seq := [][]int{
+		[]int{1, 0, 0, 0},
+		[]int{1, 1, 0, 0},
+		[]int{0, 1, 0, 0},
+		[]int{0, 1, 1, 0},
+		[]int{0, 0, 1, 0},
+		[]int{0, 0, 1, 1},
+		[]int{0, 0, 0, 1},
+		[]int{1, 0, 0, 1},
+	}
+
+	stepCount := len(seq) - 1
+	stepDir := 2 // Set to 1 or 2 for clockwise, -1 or -2 for counter-clockwise
+
+	// Start main loop
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, os.Interrupt, os.Kill)
+	defer signal.Stop(quit)
+
+	stepCounter := 0
+	for {
+		select {
+		case <-time.After(time.Duration(*stepWait) * time.Millisecond):
+			for i, pin := range stepPins {
+				if seq[stepCounter][i] != 0 {
+					fmt.Printf("Enable pin %d, step %d\n", i, stepCounter)
+					if err := pin.Write(embd.High); err != nil {
+						panic(err)
+					}
+				} else {
+					if err := pin.Write(embd.Low); err != nil {
+						panic(err)
+					}
+
+				}
+			}
+			stepCounter += stepDir
+
+			// If we reach the end of the sequence start again
+			if stepCounter >= stepCount {
+				stepCounter = 0
+			} else if stepCounter < 0 {
+				stepCounter = stepCount
+			}
+		case <-quit:
+			return
+		}
+	}
+
+}