3 files changed, 103 insertions, 3 deletions

diff --git a/software/communication/data_link.go b/software/communication/data_link.go
new file mode 100644
index 0000000..d6e752d
--- /dev/null
+++ b/software/communication/data_link.go
@@ -0,0 +1,63 @@
+package communication
+
+const (
+	SLIP_END         = 0xC0
+	SLIP_ESC         = 0xDB
+	SLIP_ESC_END     = 0xDC
+	SLIP_ESC_ESC     = 0xDD
+	SLIP_MAX_PAYLOAD = 1500
+)
+
+type dataLink struct {
+	rx chan []byte
+}
+
+func newDataLink() dataLink {
+	dl := dataLink{}
+
+	dl.rx = make(chan []byte)
+
+	return dl
+}
+
+func (dl *dataLink) start(source chan byte) {
+	go dl.receive(source)
+}
+
+func (dl *dataLink) receive(source chan byte) {
+	for {
+		frame := unslip(source)
+		dl.rx <- frame
+	}
+}
+
+func unslip(source chan byte) []byte {
+	escaped := false
+	buffer := make([]byte, 0)
+
+	for {
+		octet := <-source
+		if escaped {
+			switch octet {
+			case SLIP_ESC_END:
+				buffer = append(buffer, SLIP_END)
+			case SLIP_ESC_ESC:
+				buffer = append(buffer, SLIP_ESC)
+			}
+		} else {
+			switch octet {
+			case SLIP_END:
+				break
+			case SLIP_ESC:
+				escaped = true
+				continue
+			default:
+				buffer = append(buffer, octet)
+				continue
+			}
+			break
+		}
+	}
+
+	return buffer
+}
diff --git a/software/communication/data_link_test.go b/software/communication/data_link_test.go
new file mode 100644
index 0000000..91b941d
--- /dev/null
+++ b/software/communication/data_link_test.go
@@ -0,0 +1,33 @@
+package communication
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestUnslip(t *testing.T) {
+	input := []byte{
+		0xFF, 0x12, SLIP_END,
+	}
+
+	bytes := make(chan byte)
+	frames := make(chan []byte)
+
+	go func() {
+		for _, v := range input {
+			bytes <- v
+		}
+	}()
+
+	go func() {
+		for {
+			frames <- unslip(bytes)
+		}
+	}()
+
+	frame := <-frames
+	expected := []byte{0xFF, 0x12}
+	if !reflect.DeepEqual(frame, expected) {
+		t.Fatalf("Frame '%v' does not match expected '%v'\n", frame, expected)
+	}
+}
diff --git a/software/communication/interface.go b/software/communication/interface.go
index d124a48..df089f2 100644
--- a/software/communication/interface.go
+++ b/software/communication/interface.go
@@ -1,11 +1,12 @@
 package communication
 
 import (
-	"fmt"
+	"log"
 )
 
 type SerialInterface struct {
 	phy physical
+	dl  dataLink
 }
 
 func NewSerialInterface() (SerialInterface, error) {
@@ -17,16 +18,19 @@ func NewSerialInterface() (SerialInterface, error) {
 		return iface, err
 	}
 
+	iface.dl = newDataLink()
+
 	return iface, nil
 }
 
 func (i *SerialInterface) Start() {
 	i.phy.start()
+	i.dl.start(i.phy.rx)
 }
 
 func (i *SerialInterface) Cat() {
 	for {
-		data := <-i.phy.rx
-		fmt.Printf("%s", string(data))
+		data := <-i.dl.rx
+		log.Printf("RX: '%v'\n", data)
 	}
 }