libusb-1.0 - Where does the data go after a successful libusb_bulk_transfer() call?

问题

I ran the following code sample obtained from a tutorial here: http://www.dreamincode.net/forums/topic/148707-introduction-to-using-libusb-10/

I ran it against a tablet running Android 4 attached via USB to a MacBook Pro running Mac OS X Mountain Lion.
The output contained "Writing Successful!" so I assume libusb_bulk_transfer() worked correctly. My question is where did the 4 bytes of data got transferred to? Can I save it to a file on the Android tablet?

Thanks for your help!

#include <iostream>
#include <libusb.h>

using namespace std;

int main() {
    libusb_device **devs; //pointer to pointer of device, used to retrieve a list of devices
    libusb_device_handle *dev_handle; //a device handle
    libusb_context *ctx = NULL; //a libusb session
    int r; //for return values
    ssize_t cnt; //holding number of devices in list
    r = libusb_init(&ctx); //initialize the library for the session we just declared
    if(r < 0) {
        cout<<"Init Error "<<r<<endl; //there was an error
        return 1;
    }
    libusb_set_debug(ctx, 3); //set verbosity level to 3, as suggested in the documentation

    cnt = libusb_get_device_list(ctx, &devs); //get the list of devices
    if(cnt < 0) {
        cout<<"Get Device Error"<<endl; //there was an error
        return 1;
    }
    cout<<cnt<<" Devices in list."<<endl;

    dev_handle = libusb_open_device_with_vid_pid(ctx, 5118, 7424); //these are vendorID and productID I found for my usb device
    if(dev_handle == NULL)
        cout<<"Cannot open device"<<endl;
    else
        cout<<"Device Opened"<<endl;
    libusb_free_device_list(devs, 1); //free the list, unref the devices in it

    unsigned char *data = new unsigned char[4]; //data to write
    data[0]='a';data[1]='b';data[2]='c';data[3]='d'; //some dummy values

    int actual; //used to find out how many bytes were written
    if(libusb_kernel_driver_active(dev_handle, 0) == 1) { //find out if kernel driver is attached
        cout<<"Kernel Driver Active"<<endl;
        if(libusb_detach_kernel_driver(dev_handle, 0) == 0) //detach it
            cout<<"Kernel Driver Detached!"<<endl;
    }
    r = libusb_claim_interface(dev_handle, 0); //claim interface 0 (the first) of device (mine had jsut 1)
    if(r < 0) {
        cout<<"Cannot Claim Interface"<<endl;
        return 1;
    }
    cout<<"Claimed Interface"<<endl;

    cout<<"Data->"<<data<<"<-"<<endl; //just to see the data we want to write : abcd
    cout<<"Writing Data..."<<endl;
    r = libusb_bulk_transfer(dev_handle, (2 | LIBUSB_ENDPOINT_OUT), data, 4, &actual, 0); //my device's out endpoint was 2, found with trial- the device had 2 endpoints: 2 and 129
    if(r == 0 && actual == 4) //we wrote the 4 bytes successfully
        cout<<"Writing Successful!"<<endl;
    else
        cout<<"Write Error"<<endl;

    r = libusb_release_interface(dev_handle, 0); //release the claimed interface
    if(r!=0) {
        cout<<"Cannot Release Interface"<<endl;
        return 1;
    }
    cout<<"Released Interface"<<endl;

    libusb_close(dev_handle); //close the device we opened
    libusb_exit(ctx); //needs to be called to end the

    delete[] data; //delete the allocated memory for data
    return 0;
}

回答1:

The libusb_bulk_transfer() function writes the data at the specified endpoint. Its an address, access it, print it, or you can copy it, do some case conversion and dump it to an outgoing endpoint. And, then perform a read through libusb_bulk_transfer()

来源：https://stackoverflow.com/questions/13734008/libusb-1-0-where-does-the-data-go-after-a-successful-libusb-bulk-transfer-ca

标签

usb

libusb-1.0