我终于想到了从串行USB设备读取数据的想法。所以我想我会分享它：
首先，连接所有 USB 设备（如果多个）并获取合适的接口并搜索要通信的端点。初始化 USB 设备时，请确保考虑您真正想要与之通信的 USB 设备。您可以通过考虑产品 ID 和供应商 ID 来做到这一点。
执行上述操作的代码..
private boolean searchEndPoint() {
usbInterface = null;//class level variables, declare these.
endpointOut = null;
endpointIn = null;
Log.d("USB","Searching device and endpoints...");
if (device == null) {
usbDevices = usbManager.getDeviceList();
Iterator<UsbDevice> deviceIterator = usbDevices.values().iterator();
while (deviceIterator.hasNext()) {
UsbDevice tempDevice = deviceIterator.next();
/**Search device for targetVendorID(class level variables[vendorId = SOME_NUMBER and productId=SOME_NUMBER] which u can find) and targetProductID.*/
if (tempDevice .getVendorId() == vendorId) {
if (tempDevice .getProductId() == productId) {
device = tempDevice ;
}
}
}
}
if (device == null){
Log.d("USB","The device with specified VendorId and ProductId not found");
return false;
}
else
Log.d("USB","device found");
/**Search for UsbInterface with Endpoint of USB_ENDPOINT_XFER_BULK,
*and direction USB_DIR_OUT and USB_DIR_IN
*/
try{
for (int i = 0; i < device.getInterfaceCount(); i++) {
UsbInterface usbif = device.getInterface(i);
UsbEndpoint tOut = null;
UsbEndpoint tIn = null;
int tEndpointCnt = usbif.getEndpointCount();
if (tEndpointCnt >= 2) {
for (int j = 0; j < tEndpointCnt; j++) {
if (usbif.getEndpoint(j).getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
if (usbif.getEndpoint(j).getDirection() == UsbConstants.USB_DIR_OUT) {
tOut = usbif.getEndpoint(j);
} else if (usbif.getEndpoint(j).getDirection() == UsbConstants.USB_DIR_IN) {
tIn = usbif.getEndpoint(j);
}
}
}
if (tOut != null && tIn != null) {
/** This interface have both USB_DIR_OUT
* And USB_DIR_IN of USB_ENDPOINT_XFER_BULK
*/
usbInterface = usbif;
endpointOut = tOut;
endpointIn = tIn;
}
}
}
if (usbInterface == null) {
Log.d("USB","No suitable interface found!");
return false;
} else {
Log.d("USB","Suitable interface found!");
return true;
}
}catch(Exception ex){
ex.printStackTrace();
return false;
}
}
现在您已经拥有了可以进行通信的设备、USB 接口和端点。现在是时候在 Android 设备和 USB 设备之间建立连接了。
以下是相关代码（并检查连接是否已建立并正在通信）：
private boolean checkUsbCOMM() {
/**Value for setting request, on the USB connection.*/
final int RQSID_SET_CONTROL_LINE_STATE = 0x22;
boolean success = false;
Log.d("USB","Checking USB Device for communication: ");
try{
Boolean permitToRead = SUSBS_usbManager.hasPermission(SUSBS_device);
if (permitToRead) {
//class level variable(connection, usbManager : declare it)
connection = usbManager.openDevice(device);
if (connection != null) {
connection.claimInterface(usbInterface, true);
int usbResult;
usbResult = connection.controlTransfer(0x21, //requestType
RQSID_SET_CONTROL_LINE_STATE, //SET_CONTROL_LINE_STATE(request)
0, //value
0, //index
null, //buffer
0, //length
500); //timeout = 500ms
Log.i("USB","controlTransfer(SET_CONTROL_LINE_STATE)[must be 0 or greater than 0]: "+usbResult);
if(usbResult >= 0)
success = true;
else
success = false;
}
}
else {
/**If permission is not there then ask for permission*/
usbManager.requestPermission(device, mPermissionIntent);
Log.d("USB","Requesting Permission to access USB Device: ");
}
return success;
}catch(Exception ex){
ex.printStackTrace();
return false;
}
}
瞧，USB 设备现在可以进行通信了。那么让我们使用单独的线程来阅读：
if(device!=null){
Thread readerThread = new Thread(){
public void run(){
int usbResult = -1000;
int totalBytes = 0;
StringBuffer sb = new StringBuffer();
String usbReadResult=null;
byte[] bytesIn ;
try {
while(true){
/**Reading data until there is no more data to receive from USB device.*/
bytesIn = new byte[endpointIn.getMaxPacketSize()];
usbResult = connection.bulkTransfer(endpointIn,
bytesIn, bytesIn.length, 500);
/**The data read during each bulk transfer is logged*/
Log.i("USB","data-length/read: "+usbResult);
/**The USB result is negative when there is failure in reading or
* when there is no more data to be read[That is :
* The USB device stops transmitting data]*/
if(usbResult < 0){
Log.d("USB","Breaking out from while, usb result is -1");
break;
}
/**Total bytes read from the USB device*/
totalBytes = totalBytes+usbResult;
Log.i("USB","TotalBytes read: "+totalBytes);
for(byte b: bytesIn){
if(b == 0 )
break;
else{
sb.append((char) b);
}
}
}
/**Converting byte data into characters*/
usbReadResult = new String(sb);
Log.d("USB","The result: "+usbReadResult);
//usbResult holds the data read.
} catch (Exception ex) {
ex.printStackTrace();
}
}
};
/**Starting thread to read data from USB.*/
SUSBS_readerThread.start();
SUSBS_readerThread.join();
}
为了获得许可，请确保添加PendingIntent以及将权限添加到您的清单中。
Android 清单：<uses-feature android:name="android.hardware.usb.host" />
待定意图：
private PendingIntent mPermissionIntent;
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
mPermissionIntent = PendingIntent.getBroadcast(MainActivity.this,
0, new Intent(ACTION_USB_PERMISSION), 0);
/**Setting up the Broadcast receiver to request a permission to allow the APP to access the USB device*/
IntentFilter filterPermission = new IntentFilter(ACTION_USB_PERMISSION);
registerReceiver(mUsbReceiver, filterPermission);
