安卓免驱实现CH340、341串口通信APP开发实例

CH340/CH341 USB转串口安卓免驱应用开发

开发环境准备 安装Android Studio最新版本 添加USB转串口库依赖：在build.gradle中添加implementation 'com.github.licheedev:Android-SerialPort-API:2.1.1' 确保设备支持OTG功能并在AndroidManifest.xml中添加USB权限声明：

<uses-feature android:name="android.hardware.usb.host"/>
<uses-permission android:name="android.permission.USB_PERMISSION"/>

USB设备检测与权限处理

创建USB设备过滤器res/xml/device_filter.xml：

<resources>
    <usb-device vendor-id="6790" product-id="29987"/> <!-- CH340 -->
    <usb-device vendor-id="6790" product-id="21795"/> <!-- CH341 -->
</resources>

在Activity中注册USB设备插拔广播：

IntentFilter filter = new IntentFilter();
filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
registerReceiver(mUsbReceiver, filter);

处理USB权限请求：

private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(intent.getAction())) {
            UsbDevice device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
            if(device != null && isSupportedDevice(device)){
                requestUsbPermission(device);
            }
        }
    }
};

串口通信初始化

获取USB设备并打开串口：

UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
UsbSerialPort port = UsbSerialProber.getDefaultProber().probeDevice(usbDevice);
if(port != null){
    UsbSerialDriver driver = port.getDriver();
    if(driver instanceof Ch340SerialDriver){
        // CH34x specific initialization
        port.open(usbManager.openDevice(usbDevice));
        port.setParameters(115200, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE);
    }
}

数据收发实现

创建数据接收线程：

class SerialReadThread extends Thread {
    public void run() {
        byte[] buffer = new byte[1024];
        while(!isInterrupted()){
            int len = port.read(buffer, 1000);
            if(len > 0){
                final String data = new String(buffer, 0, len);
                runOnUiThread(() -> receiveData(data));
            }
        }
    }
}

实现数据发送方法：

public void sendData(String data) {
    try {
        byte[] bytes = data.getBytes();
        port.write(bytes, 1000);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

错误处理与资源释放

实现异常处理机制：

try {
    port.setDTR(true);
    port.setRTS(true);
} catch (IOException e) {
    showError("设备控制失败：" + e.getMessage());
}

正确释放资源：

@Override
protected void onDestroy() {
    super.onDestroy();
    if(port != null){
        try {
            port.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    unregisterReceiver(mUsbReceiver);
}

波特率配置优化

CH34x系列支持的波特率范围：

private static final int[] BAUD_RATES = {
    50, 75, 100, 110, 134, 150, 200, 300, 600,
    1200, 1800, 2400, 4800, 9600, 19200, 38400,
    57600, 115200, 230400, 460800, 921600
};

public void setBaudRate(int baudRate) throws IOException {
    if(Arrays.binarySearch(BAUD_RATES, baudRate) < 0){
        throw new IllegalArgumentException("不支持的波特率");
    }
    port.setParameters(baudRate, dataBits, stopBits, parity);
}

流控制实现

硬件流控制配置：

public void setFlowControl(int flowControl) {
    try {
        switch(flowControl){
            case FLOW_CONTROL_OFF:
                port.setRTS(false);
                port.setDTR(false);
                break;
            case FLOW_CONTROL_RTS_CTS:
                port.setRTS(true);
                port.setDTR(false);
                break;
            case FLOW_CONTROL_DSR_DTR:
                port.setRTS(false);
                port.setDTR(true);
                break;
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

性能优化技巧

使用缓冲区提高收发效率：

ByteArrayOutputStream receiveBuffer = new ByteArrayOutputStream();
private static final int BUFFER_SIZE = 4096;

void readData() throws IOException {
    byte[] tempBuffer = new byte[BUFFER_SIZE];
    int len;
    while((len = port.read(tempBuffer, 0)) > 0){
        receiveBuffer.write(tempBuffer, 0, len);
        processCompletePackets();
    }
}

完整示例项目结构

典型项目结构：

app/
├── libs/
├── src/
│   ├── main/
│   │   ├── java/com/example/serialapp/
│   │   │   ├── SerialService.java
│   │   │   ├── MainActivity.java
│   │   │   └── utils/
│   │   │       ├── SerialUtils.java
│   │   │       └── ProtocolParser.java
│   │   ├── res/
│   │   │   ├── xml/
│   │   │   │   └── device_filter.xml
│   │   │   └── layout/
│   │   │       └── activity_main.xml
│   │   └── AndroidManifest.xml
└── build.gradle

常见问题解决方案

CH34x设备不识别问题： 检查设备VID/PID是否匹配：CH340通常为VID_1A86/PID_7523 确保已安装正确的USB驱动，部分设备需要手动加载驱动

数据收发不完整问题： 增加超时设置和缓冲区管理 校验数据包的起始和结束标记 实现数据分包和组包逻辑

兼容性问题处理：

public static boolean isCh34xDevice(UsbDevice device) {
    return (device.getVendorId() == 0x1A86 && 
           (device.getProductId() == 0x7523 || 
            device.getProductId() == 0x5523));
}