diff --git a/device.go b/device.go
index 5b5d47e1..9b197369 100644
--- a/device.go
+++ b/device.go
@@ -5,6 +5,12 @@ import (
 	"reflect"
 )
 
+type Device interface {
+	Init() bool
+	Start() bool
+	Halt() bool
+}
+
 type device struct {
 	Name     string          `json:"name"`
 	Type     string          `json:"driver"`
@@ -13,10 +19,13 @@ type device struct {
 	Driver   DriverInterface `json:"-"`
 }
 
-type Device interface {
-	Init() bool
-	Start() bool
-	Halt() bool
+type devices []*device
+
+// Halt() stop all the devices.
+func (d devices) Halt() {
+	for _, device := range d {
+		device.Halt()
+	}
 }
 
 func NewDevice(driver DriverInterface, r *Robot) *device {
diff --git a/master.go b/master.go
index 2daa5ec3..f6a8289f 100644
--- a/master.go
+++ b/master.go
@@ -42,7 +42,7 @@ func (m *Master) Start() {
 	// waiting on something coming on the channel
 	_ = <-c
 	for _, r := range m.Robots {
-		r.haltDevices()
+		r.GetDevices().Halt()
 		r.finalizeConnections()
 	}
 
diff --git a/robot.go b/robot.go
index 07d94651..fff6997e 100644
--- a/robot.go
+++ b/robot.go
@@ -113,20 +113,14 @@ func (r *Robot) startDevices() bool {
 	return success
 }
 
-func (r *Robot) haltDevices() {
-	for _, device := range r.devices {
-		device.Halt()
-	}
-}
-
 func (r *Robot) finalizeConnections() {
 	for _, connection := range r.connections {
 		connection.Finalize()
 	}
 }
 
-func (r *Robot) GetDevices() []*device {
-	return r.devices
+func (r *Robot) GetDevices() devices {
+	return devices(r.devices)
 }
 
 func (r *Robot) GetDevice(name string) *device {