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usblibusb

Read/write on a pen drive using libusb: libusb_bulk_transfer()


I am trying to perform read and write operations on a pen drive.

Details: Vendor ID: 8564 and Product ID: 1000. It is a Transcend JetFlash mass storage device.

I am keen to know that whether it is possible to achieve a read/write on a pen drive. If it is, then is it going to happen the way I have tried in the code provided below.

I have learnt the methods to get the device id, product id and endpoint addresses. This is what I have implemented.

Here the device is getting acknowledged and opened. And, even the interface claims it is successful.

But bulk transfer functions return -1.

What is the explanation?

#include <stdio.h>
#include <sys/types.h>
#include <string.h>
#include </usr/include/libusb-1.0/libusb.h>

#define BULK_EP_OUT     0x82
#define BULK_EP_IN      0x02

int main(void)
{
    int r = 0, e = 0;
    struct libusb_device_handle *handle = NULL;
    struct libusb_device **devs;
    struct libusb_device *dev;
    struct libusb_device_descriptor desc;
    char str1[256], str2[256];

    /* Init libusb */
    r = libusb_init(NULL);
    if (r < 0)
    {
        printf("\nfailed to initialise libusb\n");
        return 1;
    }

    handle = libusb_open_device_with_vid_pid(NULL, 0x8564, 0x1000);
    if(handle == NULL)
    {
        printf("\nError in device opening!");
    }
    else
        printf("\nDevice Opened");

    // Tell libusb to use the CONFIGNUM configuration of the device

    libusb_set_configuration(handle, 1);
    if(libusb_kernel_driver_active(handle, 0) == 1)
    {
        printf("\nKernel Driver Active");
        if(libusb_detach_kernel_driver(handle, 0) == 0)
            printf("\nKernel Driver Detached!");
    }

    e = libusb_claim_interface(handle, 0);
    if(e < 0)
    {
        printf("\nCannot Claim Interface");
    }
    else
        printf("\nClaimed Interface");

      /* Communicate */

    int bytes_read;
    int nbytes = 256;
    unsigned char *my_string, *my_string1;
    int transferred = 0;
    my_string = (unsigned char *) malloc (nbytes + 1);
    my_string1 = (unsigned char *) malloc (nbytes + 1);

    strcpy(my_string, "divesd");
    printf("\nTo be sent : %s", my_string);

    e = libusb_bulk_transfer(handle, BULK_EP_OUT, my_string, bytes_read, &transferred, 5000);
    printf("\nXfer returned with %d", e);
    printf("\nSent %d bytes with string: %s\n", transferred, my_string);

    libusb_bulk_transfer(handle, BULK_EP_IN, my_string1, 256, &transferred, 5000);
    printf("\nXfer returned with %d", e);     //It returns -1... This is an error, I guess.
    printf("\nReceived %d bytes with string: %s\n", transferred, my_string1);

    e = libusb_release_interface(handle, 0);
    libusb_close(handle);
    libusb_exit(NULL);
    return 0;
}

Solution

  • Try the code given below and it should work on LPC2148. I have tested this with an LPC2148 configured to receive an interrupt from USB after a write happens (from user-space) and the RTC starts running.

    Answering to your question whether it involves a kernel driver in read/write or not: As far as I have studied, you have to detach the kernel driver and claim the interface using libusb APIs. Though I am not sure whether it can be done without detaching it or not.

    #include <stdio.h>
    #include <stdlib.h>
    #include <sys/types.h>
    #include <string.h>
    #include </usr/local/include/libusb-1.0/libusb.h>
    
    #define BULK_EP_OUT     0x82
    #define BULK_EP_IN      0x08
    
    int interface_ref = 0;
    int alt_interface, interface_number;
    
    int print_configuration(struct libusb_device_handle *hDevice, struct libusb_config_descriptor *config)
    {
        char *data;
        int index;
    
        data = (char *)malloc(512);
        memset(data, 0, 512);
    
        index = config->iConfiguration;
    
        libusb_get_string_descriptor_ascii(hDevice, index, data, 512);
    
        printf("\nInterface Descriptors: ");
        printf("\n\tNumber of Interfaces: %d", config->bNumInterfaces);
        printf("\n\tLength: %d", config->bLength);
        printf("\n\tDesc_Type: %d", config->bDescriptorType);
        printf("\n\tConfig_index: %d", config->iConfiguration);
        printf("\n\tTotal length: %lu", config->wTotalLength);
        printf("\n\tConfiguration Value: %d", config->bConfigurationValue);
        printf("\n\tConfiguration Attributes: %d", config->bmAttributes);
        printf("\n\tMaxPower(mA): %d\n", config->MaxPower);
    
        free(data);
        data = NULL;
        return 0;
    }
    
    struct libusb_endpoint_descriptor* active_config(struct libusb_device *dev, struct libusb_device_handle *handle)
    {
        struct libusb_device_handle *hDevice_req;
        struct libusb_config_descriptor *config;
        struct libusb_endpoint_descriptor *endpoint;
        int altsetting_index, interface_index=0, ret_active;
        int i, ret_print;
    
        hDevice_req = handle;
    
        ret_active = libusb_get_active_config_descriptor(dev, &config);
        ret_print = print_configuration(hDevice_req, config);
    
        for (interface_index=0;interface_index<config->bNumInterfaces;interface_index++)
        {
            const struct libusb_interface *iface = &config->interface[interface_index];
            for (altsetting_index=0; altsetting_index<iface->num_altsetting; altsetting_index++)
            {
                const struct libusb_interface_descriptor *altsetting = &iface->altsetting[altsetting_index];
    
                int endpoint_index;
                for(endpoint_index=0; endpoint_index<altsetting->bNumEndpoints; endpoint_index++)
                {
                    const struct libusb_endpoint_desriptor *ep = &altsetting->endpoint[endpoint_index];
                    endpoint = ep;
                    alt_interface = altsetting->bAlternateSetting;
                    interface_number = altsetting->bInterfaceNumber;
                }
    
                printf("\nEndPoint Descriptors: ");
                printf("\n\tSize of EndPoint Descriptor: %d", endpoint->bLength);
                printf("\n\tType of Descriptor: %d", endpoint->bDescriptorType);
                printf("\n\tEndpoint Address: 0x0%x", endpoint->bEndpointAddress);
                printf("\n\tMaximum Packet Size: %x", endpoint->wMaxPacketSize);
                printf("\n\tAttributes applied to Endpoint: %d", endpoint->bmAttributes);
                printf("\n\tInterval for Polling for data Tranfer: %d\n", endpoint->bInterval);
            }
        }
        libusb_free_config_descriptor(NULL);
        return endpoint;
    }
    
    int main(void)
    {
        int r = 1;
        struct libusb_device **devs;
        struct libusb_device_handle *handle = NULL, *hDevice_expected = NULL;
        struct libusb_device *dev, *dev_expected;
    
        struct libusb_device_descriptor desc;
        struct libusb_endpoint_descriptor *epdesc;
        struct libusb_interface_descriptor *intdesc;
    
        ssize_t cnt;
        int e = 0, config2;
        int i = 0, index;
        char str1[64], str2[64];
        char found = 0;
    
        // Init libusb
        r = libusb_init(NULL);
        if(r < 0)
        {
            printf("\nFailed to initialise libusb\n");
            return 1;
        }
        else
            printf("\nInit successful!\n");
    
        // Get a list of USB devices
        cnt = libusb_get_device_list(NULL, &devs);
        if (cnt < 0)
        {
            printf("\nThere are no USB devices on the bus\n");
            return -1;
        }
        printf("\nDevice count: %d\n-------------------------------\n", cnt);
    
        while ((dev = devs[i++]) != NULL)
        {
            r = libusb_get_device_descriptor(dev, &desc);
            if (r < 0)
                {
                printf("Failed to get device descriptor\n");
                libusb_free_device_list(devs, 1);
                libusb_close(handle);
                break;
            }
    
            e = libusb_open(dev, &handle);
            if (e < 0)
            {
                printf("Error opening device\n");
                libusb_free_device_list(devs, 1);
                libusb_close(handle);
                break;
            }
    
            printf("\nDevice Descriptors: ");
            printf("\n\tVendor ID: %x", desc.idVendor);
            printf("\n\tProduct ID: %x", desc.idProduct);
            printf("\n\tSerial Number: %x", desc.iSerialNumber);
            printf("\n\tSize of Device Descriptor: %d", desc.bLength);
            printf("\n\tType of Descriptor: %d", desc.bDescriptorType);
            printf("\n\tUSB Specification Release Number: %d", desc.bcdUSB);
            printf("\n\tDevice Release Number: %d", desc.bcdDevice);
            printf("\n\tDevice Class: %d", desc.bDeviceClass);
            printf("\n\tDevice Sub-Class: %d", desc.bDeviceSubClass);
            printf("\n\tDevice Protocol: %d", desc.bDeviceProtocol);
            printf("\n\tMax. Packet Size: %d", desc.bMaxPacketSize0);
            printf("\n\tNumber of Configurations: %d\n", desc.bNumConfigurations);
    
            e = libusb_get_string_descriptor_ascii(handle, desc.iManufacturer, (unsigned char*) str1, sizeof(str1));
            if (e < 0)
            {
            libusb_free_device_list(devs, 1);
                libusb_close(handle);
                break;
            }
            printf("\nManufactured: %s", str1);
    
            e = libusb_get_string_descriptor_ascii(handle, desc.iProduct, (unsigned char*) str2, sizeof(str2));
            if(e < 0)
            {
            libusb_free_device_list(devs, 1);
                libusb_close(handle);
                break;
            }
            printf("\nProduct: %s", str2);
            printf("\n----------------------------------------");
    
            if(desc.idVendor == 0xffff && desc.idProduct == 0x4)
            {
               found = 1;
            break;
            }
        }//end of while
        if(found == 0)
        {
            printf("\nDevice NOT found\n");
            libusb_free_device_list(devs, 1);
            libusb_close(handle);
            return 1;
        }
        else
        {
            printf("\nDevice found");
            dev_expected = dev;
            hDevice_expected = handle;
        }
    
        e = libusb_get_configuration(handle, &config2);
        if(e!=0)
        {
            printf("\n***Error in libusb_get_configuration\n");
            libusb_free_device_list(devs, 1);
            libusb_close(handle);
            return -1;
        }
        printf("\nConfigured value: %d", config2);
    
        if(config2 != 1)
        {
            libusb_set_configuration(handle, 1);
            if(e!=0)
            {
                printf("Error in libusb_set_configuration\n");
                libusb_free_device_list(devs, 1);
                libusb_close(handle);
                return -1;
            }
            else
                printf("\nDevice is in configured state!");
        }
    
        libusb_free_device_list(devs, 1);
    
        if(libusb_kernel_driver_active(handle, 0) == 1)
        {
            printf("\nKernel Driver Active");
            if(libusb_detach_kernel_driver(handle, 0) == 0)
                printf("\nKernel Driver Detached!");
            else
            {
                printf("\nCouldn't detach kernel driver!\n");
                libusb_free_device_list(devs, 1);
                libusb_close(handle);
                return -1;
            }
        }
    
        e = libusb_claim_interface(handle, 0);
        if(e < 0)
        {
            printf("\nCannot Claim Interface");
            libusb_free_device_list(devs, 1);
            libusb_close(handle);
            return -1;
        }
        else
            printf("\nClaimed Interface\n");
    
        active_config(dev_expected, hDevice_expected);
    
        //   Communicate
    
        char *my_string, *my_string1;
        int transferred = 0;
        int received = 0;
        int length = 0;
    
        my_string = (char *)malloc(nbytes + 1);
        my_string1 = (char *)malloc(nbytes + 1);
    
        memset(my_string, '\0', 64);
        memset(my_string1, '\0', 64);
    
        strcpy(my_string, "Prasad Divesd");
        length = strlen(my_string);
    
        printf("\nTo be sent: %s", my_string);
    
        e = libusb_bulk_transfer(handle, BULK_EP_IN, my_string, length, &transferred, 0);
        if(e == 0 && transferred == length)
        {
            printf("\nWrite successful!");
            printf("\nSent %d bytes with string: %s\n", transferred, my_string);
        }
        else
            printf("\nError in write! e = %d and transferred = %d\n", e, transferred);
    
        sleep(3);
        i = 0;
    
        for(i = 0; i < length; i++)
        {
            e = libusb_bulk_transfer(handle, BULK_EP_OUT, my_string1, 64, &received, 0);  //64: Max Packet Length
            if(e == 0)
            {
                printf("\nReceived: ");
                printf("%c", my_string1[i]); //Will read a string from LPC2148
                sleep(1);
            }
            else
            {
                printf("\nError in read! e = %d and received = %d\n", e, received);
                return -1;
            }
        }
    
        e = libusb_release_interface(handle, 0);
    
        libusb_close(handle);
        libusb_exit(NULL);
    
        printf("\n");
        return 0;
    }