feat: split out transports module, add tinygo uart transport (#4)

* feat: split out transports module, add tinygo uart transport

* transports/mcu: corrections needed to run correctly on bare-metal microcontrollers (#7)

---------

Co-authored-by: Ron Evans <ron@hybridgroup.com>

Author: HipsterBrown

README.md

@@ -570,6 +570,71 @@ func main() {
 }
 ```
 
+### TinyGo Support through MCU UART Transport
+
+```go
+//go:build baremetal
+
+package main
+
+import (
+	"machine"
+
+	"context"
+	"time"
+
+	"github.com/hipsterbrown/feetech-servo/feetech"
+)
+
+func main() {
+	if err := machine.UART0.Configure(machine.UARTConfig{
+		BaudRate: 1000000,
+		TX:       machine.UART_TX_PIN,
+		RX:       machine.UART_RX_PIN,
+	}); err != nil {
+		failure("Failed to configure UART:" + err.Error())
+	}
+
+	println("Starting servo example...")
+	ctx := context.Background()
+
+	// Create a new servo bus
+	bus, err := feetech.NewBus(feetech.BusConfig{
+		Port:     "0",
+		BaudRate: 1000000,
+		Protocol: feetech.ProtocolSTS,
+	})
+	if err != nil {
+		failure("Failed to create bus:" + err.Error())
+	}
+	defer bus.Close()
+
+	// Create a servo instance (defaults to STS3215)
+	servo := feetech.NewServo(bus, 1, nil)
+
+	// Detect model
+	if err := servo.DetectModel(ctx); err != nil {
+		failure("Failed to detect model:" + err.Error())
+	}
+	println("Connected to:", servo.Model().Name)
+
+	// Enable torque and move to center position
+	servo.Enable(ctx)
+	servo.SetPosition(ctx, 2048) // Center position for 12-bit servo
+
+	// Read current position
+	pos, _ := servo.Position(ctx)
+	println("Current position:", pos)
+}
+
+func failure(msg string) {
+	for {
+		println(msg)
+		time.Sleep(5 * time.Second)
+	}
+}
+```
+
 ### Testing with MockTransport
 
 ```go

_examples/mock_transport/example.go

@@ -6,11 +6,12 @@ import (
 	"log"
 
 	"github.com/hipsterbrown/feetech-servo/feetech"
+	"github.com/hipsterbrown/feetech-servo/transports"
 )
 
 func main() {
 	// For testing without hardware
-	mock := &feetech.MockTransport{
+	mock := &transports.MockTransport{
 		// Pre-load a ping response
 		ReadData: []byte{0xFF, 0xFF, 0x01, 0x02, 0x00, 0xFC},
 	}

feetech/bus.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"sync"
 	"time"
+
+	"github.com/hipsterbrown/feetech-servo/transports"
 )
 
 // Bus manages communication with servos on a Feetech bus.
@@ -63,7 +65,7 @@ func NewBus(cfg BusConfig) (*Bus, error) {
 			return nil, errors.New("either Transport or Port must be specified")
 		}
 		var err error
-		transport, err = OpenSerial(SerialConfig{
+		transport, err = transports.OpenSerial(transports.SerialConfig{
 			Port:     cfg.Port,
 			BaudRate: cfg.BaudRate,
 			Timeout:  cfg.Timeout,

feetech/bus_test.go

@@ -5,11 +5,13 @@ import (
 	"context"
 	"testing"
 	"time"
+
+	"github.com/hipsterbrown/feetech-servo/transports"
 )
 
 func TestBus_Ping(t *testing.T) {
 	// Set up mock with ping response + model number read response
-	mock := &MockTransport{}
+	mock := &transports.MockTransport{}
 	readIdx := 0
 	responses := [][]byte{
 		{0xFF, 0xFF, 0x01, 0x02, 0x00, 0xFC},             // Ping response
@@ -55,7 +57,7 @@ func TestBus_Ping(t *testing.T) {
 
 func TestBus_ReadRegister(t *testing.T) {
 	// Mock response for reading 2 bytes
-	mock := &MockTransport{
+	mock := &transports.MockTransport{
 		ReadData: []byte{0xFF, 0xFF, 0x01, 0x04, 0x00, 0x00, 0x08, 0xF2}, // Position 2048
 	}
 
@@ -82,7 +84,7 @@ func TestBus_ReadRegister(t *testing.T) {
 }
 
 func TestBus_WriteRegister(t *testing.T) {
-	mock := &MockTransport{
+	mock := &transports.MockTransport{
 		ReadData: []byte{0xFF, 0xFF, 0x01, 0x02, 0x00, 0xFC}, // Ack response
 	}
 
@@ -109,7 +111,7 @@ func TestBus_WriteRegister(t *testing.T) {
 }
 
 func TestBus_SyncWrite(t *testing.T) {
-	mock := &MockTransport{}
+	mock := &transports.MockTransport{}
 
 	bus, _ := NewBus(BusConfig{
 		Transport: mock,
@@ -139,7 +141,7 @@ func TestBus_SyncWrite(t *testing.T) {
 
 func TestBus_SyncRead(t *testing.T) {
 	// Mock two servo responses
-	mock := &MockTransport{
+	mock := &transports.MockTransport{
 		ReadData: []byte{
 			0xFF, 0xFF, 0x01, 0x04, 0x00, 0x00, 0x08, 0xF2, // ID 1, position 2048
 			0xFF, 0xFF, 0x02, 0x04, 0x00, 0x00, 0x04, 0xF5, // ID 2, position 1024
@@ -176,7 +178,7 @@ func TestBus_SyncRead(t *testing.T) {
 }
 
 func TestBus_SyncRead_SCSUnsupported(t *testing.T) {
-	mock := &MockTransport{}
+	mock := &transports.MockTransport{}
 
 	bus, _ := NewBus(BusConfig{
 		Transport: mock,
@@ -192,7 +194,7 @@ func TestBus_SyncRead_SCSUnsupported(t *testing.T) {
 }
 
 func TestBus_InvalidID(t *testing.T) {
-	mock := &MockTransport{}
+	mock := &transports.MockTransport{}
 	bus, _ := NewBus(BusConfig{Transport: mock})
 	defer bus.Close()
 
@@ -211,7 +213,7 @@ func TestBus_InvalidID(t *testing.T) {
 }
 
 func TestBus_Close(t *testing.T) {
-	mock := &MockTransport{}
+	mock := &transports.MockTransport{}
 	bus, _ := NewBus(BusConfig{Transport: mock})
 
 	err := bus.Close()
@@ -230,7 +232,7 @@ func TestBus_Close(t *testing.T) {
 }
 
 func TestBus_ClosedOperations(t *testing.T) {
-	mock := &MockTransport{}
+	mock := &transports.MockTransport{}
 	bus, _ := NewBus(BusConfig{Transport: mock})
 	bus.Close()
 
@@ -243,7 +245,7 @@ func TestBus_ClosedOperations(t *testing.T) {
 }
 
 func TestServo_Position(t *testing.T) {
-	mock := &MockTransport{
+	mock := &transports.MockTransport{
 		ReadData: []byte{0xFF, 0xFF, 0x01, 0x04, 0x00, 0x00, 0x08, 0xF2},
 	}
 
@@ -267,7 +269,7 @@ func TestServo_Position(t *testing.T) {
 }
 
 func TestServo_SetPosition(t *testing.T) {
-	mock := &MockTransport{
+	mock := &transports.MockTransport{
 		ReadData: []byte{0xFF, 0xFF, 0x01, 0x02, 0x00, 0xFC},
 	}
 
@@ -294,7 +296,7 @@ func TestServo_SetPosition(t *testing.T) {
 }
 
 func TestServo_TorqueEnable(t *testing.T) {
-	mock := &MockTransport{
+	mock := &transports.MockTransport{
 		ReadData: []byte{0xFF, 0xFF, 0x01, 0x02, 0x00, 0xFC},
 	}
 
@@ -323,7 +325,7 @@ func TestServo_TorqueEnable(t *testing.T) {
 
 func TestBus_ContextCancellation(t *testing.T) {
 	// Simulate slow transport
-	mock := &MockTransport{
+	mock := &transports.MockTransport{
 		ReadFunc: func(p []byte) (int, error) {
 			time.Sleep(500 * time.Millisecond)
 			return 0, nil

feetech/transport.go

@@ -1,12 +1,8 @@
 package feetech
 
 import (
-	"errors"
-	"fmt"
 	"io"
 	"time"
-
-	"go.bug.st/serial"
 )
 
 // Transport is the interface for low-level communication with the servo bus.
@@ -20,145 +16,3 @@ type Transport interface {
 	// Flush discards any buffered input data.
 	Flush() error
 }
-
-// SerialTransport implements Transport using a hardware serial port.
-type SerialTransport struct {
-	port     serial.Port
-	portName string
-	timeout  time.Duration
-}
-
-// SerialConfig holds configuration for opening a serial port.
-type SerialConfig struct {
-	Port     string
-	BaudRate int
-	Timeout  time.Duration
-}
-
-// OpenSerial opens a serial port with the given configuration.
-func OpenSerial(cfg SerialConfig) (*SerialTransport, error) {
-	if cfg.Port == "" {
-		return nil, errors.New("serial port path is required")
-	}
-
-	if cfg.BaudRate == 0 {
-		cfg.BaudRate = 1000000
-	}
-
-	if cfg.Timeout == 0 {
-		cfg.Timeout = time.Second
-	}
-
-	mode := &serial.Mode{
-		BaudRate: cfg.BaudRate,
-		DataBits: 8,
-		Parity:   serial.NoParity,
-		StopBits: serial.OneStopBit,
-	}
-
-	port, err := serial.Open(cfg.Port, mode)
-	if err != nil {
-		return nil, fmt.Errorf("failed to open serial port: %w", err)
-	}
-
-	if err := port.SetReadTimeout(cfg.Timeout); err != nil {
-		port.Close()
-		return nil, fmt.Errorf("failed to set read timeout: %w", err)
-	}
-
-	return &SerialTransport{
-		port:     port,
-		portName: cfg.Port,
-		timeout:  cfg.Timeout,
-	}, nil
-}
-
-func (t *SerialTransport) Read(p []byte) (int, error) {
-	return t.port.Read(p)
-}
-
-func (t *SerialTransport) Write(p []byte) (int, error) {
-	return t.port.Write(p)
-}
-
-func (t *SerialTransport) Close() error {
-	return t.port.Close()
-}
-
-func (t *SerialTransport) SetReadTimeout(timeout time.Duration) error {
-	t.timeout = timeout
-	return t.port.SetReadTimeout(timeout)
-}
-
-func (t *SerialTransport) Flush() error {
-	// Read and discard any buffered data
-	buf := make([]byte, 4096)
-	t.port.SetReadTimeout(10 * time.Millisecond)
-	for {
-		n, err := t.port.Read(buf)
-		if n == 0 || err != nil {
-			break
-		}
-	}
-	// Restore original timeout
-	t.port.SetReadTimeout(t.timeout)
-	return nil
-}
-
-// PortName returns the serial port name.
-func (t *SerialTransport) PortName() string {
-	return t.portName
-}
-
-// MockTransport implements Transport for testing.
-type MockTransport struct {
-	ReadData    []byte
-	ReadErr     error
-	WriteData   []byte
-	WriteErr    error
-	Closed      bool
-	ReadTimeout time.Duration
-	Flushed     bool
-
-	// ReadFunc allows custom read behavior for complex tests
-	ReadFunc func(p []byte) (int, error)
-}
-
-func (m *MockTransport) Read(p []byte) (int, error) {
-	if m.ReadFunc != nil {
-		return m.ReadFunc(p)
-	}
-	if m.ReadErr != nil {
-		return 0, m.ReadErr
-	}
-	n := copy(p, m.ReadData)
-	m.ReadData = m.ReadData[n:]
-	if n == 0 {
-		return 0, io.EOF
-	}
-	return n, nil
-}
-
-func (m *MockTransport) Write(p []byte) (int, error) {
-	if m.WriteErr != nil {
-		return 0, m.WriteErr
-	}
-	m.WriteData = append(m.WriteData, p...)
-	return len(p), nil
-}
-
-func (m *MockTransport) Close() error {
-	m.Closed = true
-	return nil
-}
-
-func (m *MockTransport) SetReadTimeout(timeout time.Duration) error {
-	m.ReadTimeout = timeout
-	return nil
-}
-
-func (m *MockTransport) Flush() error {
-	m.Flushed = true
-	// Don't clear ReadData - tests need to preserve mock response data
-	return nil
-}