如何在Qt中实现发送数据到USB设备的功能?
时间: 2024-10-10 16:07:22 浏览: 28
在Qt中向USB设备发送数据通常涉及到两个步骤:首先,你需要准备数据,然后通过libusb库调用USB控制请求(Control Request)或使用bulk OUT endpoint进行同步或异步数据传输。
以下是发送数据的基本步骤,假设你已经有一个初始化好的`UsbDevice`实例`device`:
1. **准备数据**:
```cpp
QByteArray sendData("Hello, USB!");
```
2. **选择传输方法**:
- **Control Request**:对于特定命令或小数据量的发送,可以使用`libusb_control_transfer`,例如:
```cpp
struct libusb_ctrl_request request = {0};
request.bmRequestType = LibusbRequestType::LIBUSB_REQUEST_TYPE_CLASS | LibusbRequestRecipient::LIBUSB_RECIPIENT_INTERFACE | LibusbRequestType::LIBUSB_REQUEST_TYPE_OUTPUT;
request.bRequest = USB_WRITE_COMMAND; // 替换为实际的请求码
request.wValue = 0x01; // 写入值
request.wIndex = 0; // 接口编号
request.wLength = sendData.size(); // 数据长度
if (libusb_control_transfer(device->devHandle, &request, sendData.data(), sendData.size(), 0, timeoutMS, &actualWriteLen)) {
if (actualWriteLen != sendData.size()) {
qWarning("Failed to send data with control request: %d bytes sent, expected %d", actualWriteLen, sendData.size());
}
} else {
qWarning("Failed to execute control transfer");
}
```
- **Bulk OUT endpoint**:对于大块数据,可以使用bulk OUT端点,比如:
```cpp
libusb_fill_bulk_transfer(&transfer, device->devHandle, USB_BULK_OUT_EP, sendData.data(), sendData.size(), NULL, 0, 5000);
if (libusb_submit_transfer(&transfer)) {
qint64 result = libusb_get_transfer_status(&transfer);
while (result == LibusbTransferStatus::LIBUSB_TRANSFER_BUSY) {
result = libusb_get_transfer_status(&transfer);
msleep(100); // 等待一段时间
}
if (result == LibusbTransferStatus::LIBUSB_TRANSFER_COMPLETED) {
qint64 bytesWritten = transfer.actual_length;
if (bytesWritten != sendData.size()) {
qWarning("Failed to write all data to bulk OUT endpoint");
}
} else {
qWarning("Error sending data with bulk OUT endpoint");
}
} else {
qWarning("Failed to submit bulk OUT transfer");
}
```
3. **错误处理**:记得检查返回的错误代码,以便在发生问题时进行适当的处理。
注意,USB设备和驱动可能对某些请求有限制,所以在实际应用中,你需要查阅相关文档了解特定设备的接口和需求。
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