Added another comminucation interface implementation.

Use ACM CDC (or another proprietary) USB serial device for communication.

Currently VID / PID of a Raspberry Pi Pico SDK CDC UART are hardcoded - see https://github.com/raspberrypi/usb-pid

RaspberryPi/apple2driver/a2io/cdcio.go

@@ -0,0 +1,147 @@
+// Copyright Terence J. Boldt (c)2020-2022
+// Use of this source code is governed by an MIT
+// license that can be found in the LICENSE file.
+
+// This file is used for communicating with the Apple II data bus via the
+// GPIO ports on the Raspberry Pi
+
+package a2io
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"time"
+
+	"go.bug.st/serial"
+	"go.bug.st/serial/enumerator"
+)
+
+var port serial.Port
+
+// CDCio is a live implementation of A2Io interface
+type CDCio struct {
+}
+
+// Init initializes the CDC driver on the Raspberry Pi
+func (a2 CDCio) Init() {
+	name := ""
+	for {
+		portInfos, err := enumerator.GetDetailedPortsList()
+		if err != nil {
+			panic(err)
+		}
+		for _, portInfo := range portInfos {
+			if portInfo.IsUSB && portInfo.VID == "2E8A" && portInfo.PID == "000A" {
+				name = portInfo.Name
+				fmt.Printf("Found CDC port %s\n", name)
+				break
+			}
+		}
+		if name != "" {
+			break
+		}
+		time.Sleep(time.Millisecond)
+	}
+
+	for {
+		var err error
+		port, err = serial.Open(name, &serial.Mode{})
+		if err == nil {
+			break;
+		}
+		var portErr *serial.PortError
+		if !errors.As(err, &portErr) || portErr.Code() != serial.PortNotFound {
+			panic(err)
+		}
+		time.Sleep(time.Millisecond)
+	}
+
+	err := port.SetReadTimeout(time.Second)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// ReadByte reads a byte from the Apple II via Raspberry Pi's CDC driver
+func (a2 CDCio) ReadByte() (byte, error) {
+	var data [1]byte
+	n, err := port.Read(data[:]);
+	if err != nil {
+		return 0, err
+	}
+	if n == 0 {
+		return 0, errors.New("timed out reading byte")
+	}
+	return data[0], nil
+}
+
+// WriteByte writes a byte to the Apple II via Raspberry Pi's CDC driver
+func (a2 CDCio) WriteByte(data byte) error {
+	_, err := port.Write([]byte{data});
+	return err
+}
+
+// ReadString reads a string from the Apple II via Raspberry Pi's CDC driver
+func (a2 CDCio) ReadString() (string, error) {
+	var inBytes bytes.Buffer
+	for {
+		inByte, err := a2.ReadByte()
+		if err != nil {
+			return "", err
+		}
+		if inByte == 0 {
+			break
+		}
+		inBytes.WriteByte(inByte)
+	}
+	return inBytes.String(), nil
+}
+
+// WriteString writes a string to the Apple II via Raspberry Pi's CDC driver
+func (a2 CDCio) WriteString(outString string) error {
+	for _, character := range outString {
+		err := a2.WriteByte(byte(character) | 128)
+		if err != nil {
+			fmt.Printf("Failed to write string\n")
+			return err
+		}
+	}
+	a2.WriteByte(0)
+	return nil
+}
+
+// WriteBlock writes 512 bytes to the Apple II via Raspberry Pi's CDC driver
+func (a2 CDCio) WriteBlock(buffer []byte) error {
+	_, err := port.Write(buffer);
+	return err
+}
+
+// ReadBlock reads 512 bytes from the Apple II via Raspberry Pi's CDC driver
+func (a2 CDCio) ReadBlock(buffer []byte) error {
+	var err error
+	for i := 0; i < 512; i++ {
+		buffer[i], err = a2.ReadByte()
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// WriteBuffer writes a buffer of bytes to the Apple II via Raspberry Pi's CDC driver
+func (a2 CDCio) WriteBuffer(buffer []byte) error {
+	_, err := port.Write(buffer);
+	return err
+}
+
+// SendCharacter is a pass-through to vt100 implementation
+func (a2 CDCio) SendCharacter(character byte) {
+	sendCharacter(a2, character)
+}
+
+// ReadCharacter is a pass-through to vt100 implementation
+func (a2 CDCio) ReadCharacter() (string, error) {
+	return readCharacter(a2)
+}

RaspberryPi/apple2driver/driver.go

@@ -9,12 +9,15 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"os"
 	"path/filepath"
 	"time"
 
+	"go.bug.st/serial"
+
 	"github.com/tjboldt/Apple2-IO-RPi/RaspberryPi/apple2driver/a2io"
 	"github.com/tjboldt/Apple2-IO-RPi/RaspberryPi/apple2driver/handlers"
 	"github.com/tjboldt/Apple2-IO-RPi/RaspberryPi/apple2driver/info"
@@ -32,11 +35,16 @@ const menuCommand = 8
 const shellCommand = 9
 
 func main() {
-	drive1, drive2 := getDriveFiles()
+	drive1, drive2, cdc := getFlags()
 
 	fmt.Printf("Starting Apple II RPi v%s...\n", info.Version)
 
-	comm := a2io.A2Gpio{}
+	var comm a2io.A2Io
+	if cdc {
+		comm = a2io.CDCio{}
+	} else {
+		comm = a2io.A2Gpio{}
+	}
 
 	handlers.SetCommunication(comm)
 	comm.Init()
@@ -68,6 +76,13 @@ func main() {
 			case shellCommand:
 				handlers.ShellCommand()
 			}
+			// the A2Io interface should be extended in one way or another
+			// to encapsulate this, e.g. by a ReadByte variant / parameter 
+		} else if cdc {
+			var portErr *serial.PortError
+			if errors.As(err, &portErr) && portErr.Code() == serial.PortClosed {
+				comm.Init()
+			}
 			// temporary workaround for busy wait loop heating up the RPi
 		} else if time.Since(lastCommandTime) > time.Millisecond*100 {
 			time.Sleep(time.Millisecond * 100)
@@ -75,9 +90,10 @@ func main() {
 	}
 }
 
-func getDriveFiles() (*os.File, *os.File) {
+func getFlags() (*os.File, *os.File, bool) {
 	var drive1Name string
 	var drive2Name string
+	var cdc bool
 
 	execName, _ := os.Executable()
 	path := filepath.Dir(execName)
@@ -87,6 +103,7 @@ func getDriveFiles() (*os.File, *os.File) {
 
 	flag.StringVar(&drive1Name, "d1", "", "A ProDOS format drive image for drive 1")
 	flag.StringVar(&drive2Name, "d2", defaultFileName, "A ProDOS format drive image for drive 2 and will be used for drive 1 if drive 1 empty")
+	flag.BoolVar(&cdc, "cdc", false, "Use ACM CDC serial device")
 	flag.Parse()
 
 	var drive1 *os.File
@@ -125,5 +142,5 @@ func getDriveFiles() (*os.File, *os.File) {
 		os.Exit(1)
 	}
 
-	return drive1, drive2
+	return drive1, drive2, cdc
 }

RaspberryPi/apple2driver/go.mod

@@ -3,7 +3,8 @@ module github.com/tjboldt/Apple2-IO-RPi/RaspberryPi/apple2driver
 go 1.16
 
 require (
-	github.com/creack/pty v1.1.17
+	github.com/creack/pty v1.1.18
 	github.com/stianeikeland/go-rpio/v4 v4.6.0
 	github.com/tjboldt/ProDOS-Utilities v0.3.0
+	go.bug.st/serial v1.3.5
 )