From 46d46a8ad0e073bcb1e5f6c2a38c7b624a4b3d33 Mon Sep 17 00:00:00 2001
From: Nathan Youngman <git@nathany.com>
Date: Tue, 9 Sep 2014 21:45:38 -0600
Subject: [PATCH] sphero: return collision data as a struct

---
 examples/sphero.go                |  2 +-
 platforms/sphero/sphero_driver.go | 24 +++++++++++++++++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/examples/sphero.go b/examples/sphero.go
index 65b35b42..556e915f 100644
--- a/examples/sphero.go
+++ b/examples/sphero.go
@@ -16,7 +16,7 @@ func main() {
 
 	work := func() {
 		gobot.On(spheroDriver.Event("collision"), func(data interface{}) {
-			fmt.Println("Collision Detected!")
+			fmt.Printf("Collision Detected! %+v\n", data)
 		})
 
 		gobot.Every(3*time.Second, func() {
diff --git a/platforms/sphero/sphero_driver.go b/platforms/sphero/sphero_driver.go
index d528dceb..f2cc5c3a 100644
--- a/platforms/sphero/sphero_driver.go
+++ b/platforms/sphero/sphero_driver.go
@@ -1,6 +1,8 @@
 package sphero
 
 import (
+	"bytes"
+	"encoding/binary"
 	"fmt"
 	"time"
 
@@ -22,6 +24,19 @@ type SpheroDriver struct {
 	responseChannel chan []uint8
 }
 
+type Collision struct {
+	// Normalized impact components (direction of the collision event):
+	X, Y, Z int16
+	// Thresholds exceeded by X (1h) and/or Y (2h) axis (bitmask):
+	Axis byte
+	// Power that cross threshold Xt + Xs:
+	XMagnitude, YMagnitude int16
+	// Sphero's speed when impact detected:
+	Speed uint8
+	// Millisecond timer
+	Timestamp uint32
+}
+
 func NewSpheroDriver(a *SpheroAdaptor, name string) *SpheroDriver {
 	s := &SpheroDriver{
 		Driver: *gobot.NewDriver(
@@ -189,7 +204,14 @@ func (s *SpheroDriver) enableStopOnDisconnect() {
 }
 
 func (s *SpheroDriver) handleCollisionDetected(data []uint8) {
-	gobot.Publish(s.Event("collision"), data)
+	// ensure data is the right length:
+	if len(data) != 22 || data[4] != 17 {
+		return
+	}
+	var collision Collision
+	buffer := bytes.NewBuffer(data[5:]) // skip header
+	binary.Read(buffer, binary.BigEndian, &collision)
+	gobot.Publish(s.Event("collision"), collision)
 }
 
 func (s *SpheroDriver) getSyncResponse(packet *packet) []byte {