带有 PC 作为 USB 主机的 Android ADK，带有 libusb，批量传输错误

Question

我正在尝试让我的 PC 成为 Android 2.3.4 设备的 USB 主机，以便能够在不需要实际“附件”的情况下开发 API。为此，我需要将 PC 设置为 USB 主机和“设备”(在我的例子中是运行 2.3.4 的 Nexus One)。

我从 http://android.serverbox.ch/ 的 libusb 代码开始作为 PC 端的基础和 Android 端的 DemoKit 代码和 Android 文档。

两者似乎可以很好地协商连接，并且接口(interface)被“声明”，但在实际尝试批量传输时死掉了。在 OSX 上，错误是 -5 (LIBUSB_ERROR_NOT_FOUND)，在 Ubuntu Linux 上(作为 root)错误是 -1 (LIBUSB_ERROR_IO)。 (每个版本的最新版本都带有最新的 libusb 1.0.8)。

这是代码。欢迎对问题发表其他评论，尽管这主要是概念验证，所以我真的只是在寻找批量传输不起作用的原因:

#include <stdio.h>
#include <libusb.h>
#include <string.h>

#define ENDPOINT_BULK_IN 0x83
#define ENDPOINT_BULK_OUT 0x03 // Have tried 0x00, 0x01 and 0x02

#define VID 0x18D1
#define PID 0x4E11

#define ACCESSORY_PID 0x2D00
#define ACCESSORY_ADB_PID 0x2D01 // Can't get this to work, if ADB is active, can't get handle on device

/*
ON OSX
gcc adktest.c -I/usr/local/include -o adktest -lusb-1.0.0 -I/usr/local/include -I/usr/local/include/libusb-1.0
ON UBUNTU
gcc adktest.c -I/usr/include -o adktest -lusb-1.0 -I/usr/include -I/usr/include/libusb-1.0

Testing on Nexus One with Gingerbread 2.3.4
*/

static int transferTest();
static int init(void);
static int shutdown(void);
static void error(int code);
static void status(int code);
static int setupAccessory(
const char* manufacturer,
const char* modelName,
const char* description,
const char* version,
const char* uri,
const char* serialNumber);

//static
static struct libusb_device_handle* handle;

int main (int argc, char *argv[]){
if(init() < 0)
    return;

if(setupAccessory(
    "PCHost",
    "PCHost1",
    "Description",
    "1.0",
    "http://www.mycompany.com",
    "SerialNumber") < 0){
    fprintf(stdout, "Error setting up accessory\n");
    shutdown();
    return -1;
};
if(transferTest() < 0){
    fprintf(stdout, "Error in transferTest\n");
    shutdown();
    return -1;
}   
shutdown();
fprintf(stdout, "Finished\n");
return 0;
}

static int transferTest(){
  // TEST BULK IN/OUT
  const static int PACKET_BULK_LEN=64;
  const static int TIMEOUT=5000;
  int r,i;
  int transferred;
  char answer[PACKET_BULK_LEN];
  char question[PACKET_BULK_LEN];
  for (i=0;i<PACKET_BULK_LEN; i++) question[i]=i;

    // ***FAILS HERE***
    r = libusb_bulk_transfer(handle, ENDPOINT_BULK_OUT, question, PACKET_BULK_LEN,
                             &transferred,TIMEOUT);
    if (r < 0) {
        fprintf(stderr, "Bulk write error %d\n", r);
        error(r);
        return r;
    }
    fprintf(stdout, "Wrote %d bytes", r);

    r = libusb_bulk_transfer(handle, ENDPOINT_BULK_IN, answer,PACKET_BULK_LEN,
                             &transferred, TIMEOUT);
    if (r < 0) {
        fprintf(stderr, "Bulk read error %d\n", r);
        error(r);
        return r;
    }
    fprintf(stdout, "Read %d bytes", r);

    if (transferred < PACKET_BULK_LEN) {
        fprintf(stderr, "Bulk transfer short read (%d)\n", r);
        error(r);
        return -1;
    }
    printf("Bulk Transfer Loop Test Result:\n");
    //     for (i=0;i< PACKET_BULK_LEN;i++) printf("%i, %i,\n ",question[i],answer[i]);
    for(i = 0;i < PACKET_BULK_LEN; i++) {
        if(i%8 == 0)
            printf("\n");
        printf("%02x, %02x; ",question[i],answer[i]);
    }
    printf("\n\n");

    return 0;

}


static int init(){
libusb_init(NULL);
if((handle = libusb_open_device_with_vid_pid(NULL, VID, PID)) == NULL){
    fprintf(stdout, "Problem acquiring handle\n");
    return -1;
}
libusb_claim_interface(handle, 0);  

return 0;
}

static int shutdown(){
if(handle != NULL)
    libusb_release_interface (handle, 0);
libusb_exit(NULL);
return 0;
}

static int setupAccessory(
const char* manufacturer,
const char* modelName,
const char* description,
const char* version,
const char* uri,
const char* serialNumber){

unsigned char ioBuffer[2];
int devVersion;
int response;

response = libusb_control_transfer(
    handle, //handle
    0xC0, //bmRequestType
    51, //bRequest
    0, //wValue
    0, //wIndex
    ioBuffer, //data
    2, //wLength
    0 //timeout
);

if(response < 0){error(response);return-1;}

devVersion = ioBuffer[1] << 8 | ioBuffer[0];
fprintf(stdout,"Version Code Device: %d\n", devVersion);

usleep(1000);//sometimes hangs on the next transfer :(

response = libusb_control_transfer(handle,0x40,52,0,0,(char*)manufacturer,strlen(manufacturer),0);
if(response < 0){error(response);return -1;}
response = libusb_control_transfer(handle,0x40,52,0,1,(char*)modelName,strlen(modelName)+1,0);
if(response < 0){error(response);return -1;}
response = libusb_control_transfer(handle,0x40,52,0,2,(char*)description,strlen(description)+1,0);
if(response < 0){error(response);return -1;}
response = libusb_control_transfer(handle,0x40,52,0,3,(char*)version,strlen(version)+1,0);
if(response < 0){error(response);return -1;}
response = libusb_control_transfer(handle,0x40,52,0,4,(char*)uri,strlen(uri)+1,0);
if(response < 0){error(response);return -1;}
response = libusb_control_transfer(handle,0x40,52,0,5,(char*)serialNumber,strlen(serialNumber)+1,0);
if(response < 0){error(response);return -1;}

fprintf(stdout,"Accessory Identification sent\n", devVersion);

response = libusb_control_transfer(handle,0x40,53,0,0,NULL,0,0);
if(response < 0){error(response);return -1;}

fprintf(stdout,"Attempted to put device into accessory mode\n", devVersion);

if(handle != NULL)
    libusb_release_interface (handle, 0);

int tries = 4;
for(;;){
    tries--;
    if((handle = libusb_open_device_with_vid_pid(NULL, VID, ACCESSORY_PID)) == NULL){
        if(tries < 0){
            return -1;
        }
    }else{
        break;
    }
    sleep(1);
}

libusb_claim_interface(handle, 0);
fprintf(stdout, "Interface claimed, ready to transfer data\n");
return 0;
}

// error reporting function left out for brevity

这是 Android 应用程序:

package com.cengen.android.pchost;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.ParcelFileDescriptor;
import com.android.future.usb.UsbAccessory;
import com.android.future.usb.UsbManager;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends Activity implements Runnable
{
  private final Logger logger = LoggerFactory.getLogger("PCHost");

  private UsbManager usbManager;

  UsbAccessory accessory;
  ParcelFileDescriptor accessoryFileDescriptor;
  FileInputStream accessoryInput;
  FileOutputStream accessoryOutput;

  private final BroadcastReceiver usbBroadcastReceiver = new BroadcastReceiver()
  {
    public void onReceive(Context context, Intent intent)
    {
      String action = intent.getAction();
      if (UsbManager.ACTION_USB_ACCESSORY_ATTACHED.equals(action))
      {
        synchronized (this)
        {
          accessory = UsbManager.getAccessory(intent);
        }
      }
      else if (UsbManager.ACTION_USB_ACCESSORY_DETACHED.equals(action))
      {
        UsbAccessory accessory = UsbManager.getAccessory(intent);
        if (accessory != null)
        {
          // call your method that cleans up and closes communication with the accessory
        }
      }
    }
  };

  Handler messageHandler = new Handler()
  {
    @Override
    public void handleMessage(Message msg)
    {
      switch (msg.what)
      {
        case 1:
          logger.info("Got message type {}", msg.what);
//              SendFileMessage m = (SendFileMessage) msg.obj;
//              handleSendFile(m);
        break;
        case 2:
          logger.info("Got message type {}", msg.what);
//              SendFileMessage m = (SendFileMessage) msg.obj;
//              handleSendFile(m);
        break;
        case 3:
          logger.info("Got message type {}", msg.what);
//              SendFileMessage m = (SendFileMessage) msg.obj;
//              handleSendFile(m);
        break;
      }
    }
  };

  /**
   * Main USB reading loop, processing incoming data from accessory and parsing
   * it into messages via the defined format.
   */
  public void run()
  {
    int ret = 0;
    byte[] buffer = new byte[16384];
    int i;

    while (ret >= 0)
    {
      try
      {
        ret = accessoryInput.read(buffer);
        logger.debug("Read {} bytes.", ret);
      }
      catch (IOException e)
      {
        logger.debug("Exception in USB accessory input reading", e);
        break;
      }

      i = 0;
      while (i < ret)
      {
        int len = ret - i;

        switch (buffer[i])
        {
          case 0x1:
            if (len >= 3)
            {
              Message m = Message.obtain(messageHandler, 1);
//                      m.obj = new MessageTypeOne(buffer[i + 1], buffer[i + 2]);
              messageHandler.sendMessage(m);
            }
            i += 3;
            break;

          case 0x4:
            if (len >= 3)
            {
              Message m = Message.obtain(messageHandler, 1);
//                      m.obj = new MessageTypeTwo(buffer[i + 1], buffer[i + 2]);
              messageHandler.sendMessage(m);
            }
            i += 3;
            break;

          default:
            logger.debug("unknown msg: " + buffer[i]);
            i = len;
            break;
        }
      }

    }
  }

  @Override
  public void onCreate(Bundle savedInstanceState)
  {
    super.onCreate(savedInstanceState);

    usbManager = UsbManager.getInstance(this);

    IntentFilter filter = new IntentFilter(UsbManager.ACTION_USB_ACCESSORY_ATTACHED);
    filter.addAction(UsbManager.ACTION_USB_ACCESSORY_DETACHED);
    registerReceiver(usbBroadcastReceiver, filter);

    if (getLastNonConfigurationInstance() != null)
    {
      accessory = (UsbAccessory) getLastNonConfigurationInstance();
      openAccessory(accessory);
    }
    setContentView(R.layout.main);
  }

  @Override
  public Object onRetainNonConfigurationInstance()
  {
    return accessory != null ? accessory : super.onRetainNonConfigurationInstance();
  }

 @Override
 public void onResume()
 {
   super.onResume();

   Intent intent = getIntent();
   if (accessoryInput != null && accessoryOutput != null)
     return;

   // TODO: verify, docs don't do this simple thing, not sure why?
   UsbAccessory accessory = UsbManager.getAccessory(intent);
   if (accessory != null)
     openAccessory(accessory);
   else
     logger.error("Failed to resume accessory.");
 }

  @Override
  public void onPause()
  {
    super.onPause();
    closeAccessory();
  }

  @Override
  public void onDestroy()
  {
    unregisterReceiver(usbBroadcastReceiver);
    super.onDestroy();
  }

  private void openAccessory(UsbAccessory accessory)
  {
    accessoryFileDescriptor = usbManager.openAccessory(accessory);
    if (accessoryFileDescriptor != null)
    {
      this.accessory = accessory;
      FileDescriptor fd = accessoryFileDescriptor.getFileDescriptor();
      accessoryInput = new FileInputStream(fd);
      accessoryOutput = new FileOutputStream(fd);
      Thread thread = new Thread(null, this, "AndroidPCHost");
      thread.start();
      logger.debug("accessory opened");
      // TODO: enable USB operations in the app
    }
    else
    {
      logger.debug("accessory open fail");
    }
  }

  private void closeAccessory()
  {
    // TODO: disable USB operations in the app
    try
    {
      if (accessoryFileDescriptor != null)
        accessoryFileDescriptor.close();
    }
    catch (IOException e)
    {}
    finally
    {
      accessoryFileDescriptor = null;
      accessory = null;
    }
  }
}

和 list (根据文档，包括 Intent 过滤，以便它自动关联和自动永久化设备):

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.mycompany.android.pchost"
      android:versionCode="1"
      android:versionName="1.0">
  <uses-feature android:name="android.hardware.usb.accessory" />
  <uses-sdk android:minSdkVersion="10" />
  <application android:label="@string/app_name" android:icon="@drawable/icon">
    <uses-library android:name="com.android.future.usb.accessory" />
        <activity android:name="MainActivity"
                  android:label="@string/app_name"
                  android:launchMode="singleInstance">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
          <intent-filter>
              <action android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED" />
          </intent-filter>

          <meta-data android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"
              android:resource="@xml/accessory_filter" />

        </activity>
    </application>
</manifest> 

Answer 1

最初的问题是为了告诉它进入附件模式而与设备的原始连接永远不会关闭。如果您随后在原始设备仍处于打开状态时重新打开并声明接口(interface)，则 USB 子系统和/或 libusb 不会抛出错误。当您实际尝试写入端点或从端点写入时，您只会收到 IO 或 NOT FOUND 错误。

通过添加:

libusb_close(handle);

在从初始连接释放初始接口(interface)的 if 语句中，问题的 libusb 端得到解决。

在这个特定的软件组合中阻止数据传递的下一个问题是，Android 端在接受读取之前等待更大的字节段，这会导致超时(由于哪个原因尚未解决)端)，因此如果您设置缓冲区以匹配 libusb 端(64)，您将获得从 PC 写入 Android 设备的一组初始字节。之后软件仍然会中断，因为 PC/libusb 端然后尝试读取数据，但 Android 端没有写入任何数据，但这只是未完成的软件，不在问题范围内。