Add Piner and Porter

adaptor.go

@@ -4,6 +4,8 @@ type Adaptor interface {
 	Finalize() []error
 	Connect() []error
 	Name() string
-	Port() string
-	String() string
+}
+
+type Porter interface {
+	Port() string
 }

connection.go

@@ -42,10 +42,13 @@ func (c *connections) Start() (errs []error) {
 	log.Println("Starting connections...")
 	for _, connection := range *c {
 		info := "Starting connection " + connection.Name()
-		if connection.Port() != "" {
-			info = info + " on port " + connection.Port()
+
+		if porter, ok := connection.(Porter); ok {
+			info = info + " on port " + porter.Port()
 		}
+
 		log.Println(info + "...")
+
 		if errs = connection.Connect(); len(errs) > 0 {
 			for i, err := range errs {
 				errs[i] = errors.New(fmt.Sprintf("Connection %q: %v", connection.Name(), err))

device.go

@@ -52,9 +52,11 @@ func (d *devices) Start() (errs []error) {
 	log.Println("Starting devices...")
 	for _, device := range *d {
 		info := "Starting device " + device.Name()
-		if device.Pin() != "" {
-			info = info + " on pin " + device.Pin()
+
+		if piner, ok := device.(Piner); ok {
+			info = info + " on pin " + piner.Pin()
 		}
+
 		log.Println(info + "...")
 		if errs = device.Start(); len(errs) > 0 {
 			for i, err := range errs {

driver.go

@@ -4,7 +4,9 @@ type Driver interface {
 	Start() []error
 	Halt() []error
 	Name() string
-	Pin() string
-	String() string
 	Connection() Connection
 }
+
+type Piner interface {
+	Pin() string
+}