Unable to receive data with libusb - c

Question

I want to send and receive data from device to pc and vice versa. I am sending the string, but not able to receive it fully. Example: Sent string is Hello, and the output is:
Received:H
Error in read! e = -4 and received = 5
#include <string.h>
#include<stdio.h>
#include <stdlib.h>
#include <libusb-1.0/libusb.h>
#define BULK_EP_OUT 0x01
#define BULK_EP_IN 0x81
/*find these values using lsusb -v*/
uint16_t VENDOR = 0x0483;
uint16_t PRODUCT = 0x5740;
int main(void)
{
int ret = 1; //int type result
struct libusb_device **usb_dev;
struct libusb_device_descriptor desc;
struct libusb_device_handle *handle = NULL;
struct device_handle_expected;
//struct libusb_device_handle device_expected_handle = NULL;
struct libusb_device *dev, *dev_expected;
char *my_string, *my_string1;
int e = 0, config;
char found = 0;
int transferred = 0;
int received = 0;
int length = 0;
int i=0;
int count;
/*struct libusb_device *dev;
struct libusb_device **devs;
struct dev_expected;*/
// Initialize libusb
ret = libusb_init(NULL);
if(ret < 0)
{
printf("\nFailed to initialise libusb\n");
return 1;
}
else
printf("\nInit successful!\n");
// Get a list of USB devices
count = libusb_get_device_list(NULL, &usb_dev);
if (count < 0)
{
printf("\nThere are no USB devices on the bus\n");
return -1;
}
printf("\nToally we have %d devices\n", count);
while ((dev = usb_dev[i++]) != NULL)
{
ret = libusb_get_device_descriptor(dev, &desc);
if (ret < 0)
{
printf("Failed to get device descriptor\n");
libusb_free_device_list(dev, 1);
break;
}
e = libusb_open(dev, &handle);
if (e < 0)
{
printf("Error opening device\n");
libusb_free_device_list(dev, 1);
libusb_close(handle);
break;
}
if(desc.idVendor == 0x0483 && desc.idProduct == 0x5740)
{
found = 1;
break;
}
}//end of while
if(found == 0)
{
printf("\nDevice NOT found\n");
libusb_free_device_list(usb_dev, 1);
libusb_close(handle);
return 1;
}
else
{
printf("\nDevice found");
// dev_expected = dev;
//device_handle_expected = handle;
}
e = libusb_get_configuration(handle, &config);
if(e!=0)
{
printf("\n***Error in libusb_get_configuration\n");
libusb_free_device_list(usb_dev, 1);
libusb_close(handle);
return -1;
}
printf("\nConfigured value: %d", config);
if(config != 1)
{
libusb_set_configuration(handle, 1);
if(e!=0)
{
printf("Error in libusb_set_configuration\n");
libusb_free_device_list(usb_dev, 1);
libusb_close(handle);
return -1;
}
else
printf("\nDevice is in configured state!");
}
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(usb_dev, 1);
libusb_close(handle);
return -1;
}
}
e = libusb_claim_interface(handle, 0);
if(e < 0)
{
printf("\nCannot Claim Interface");
libusb_free_device_list(usb_dev, 1);
libusb_close(handle);
return -1;
}
else
printf("\nClaimed Interface\n");
int nbytes = 64;
my_string = (char *) malloc(nbytes + 1);
my_string1 = (char *) malloc(nbytes + 1);
memset(my_string, '\0', 64);//The C library function void (an unsigned char) to the first n characters of the string pointed to, by the argument str.
memset(my_string1, '\0', 64);
strcpy(my_string, "Hello");
length = strlen(my_string);
printf("\nTo be sent: %s", my_string);
e = libusb_bulk_transfer(handle, BULK_EP_OUT, 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_IN, my_string1,length, &received, 0); //64: Max Packet Length
if(e == 0 && received == length)
{
printf("\nReceived:");
printf("%c", my_string1[i]);
sleep(5);
}
else
{
printf("\nError in read! e = %d and received = %d bytes\n", e, received);
return -1;
}
}
libusb_release_interface(handle, 0);
libusb_free_device_list(usb_dev, 1);
libusb_close(handle);
libusb_exit(NULL);
printf("\n");
return 0;
}

Answer 1

Pretty certain the bulk in transfer will transfer the entire buffer at once(up to 64--or 512 if you're doing high speed--bytes), not a byte at a time.
You're iterating over the size of the expected buffer and doing a bulk in for each byte, and only printing out the first byte.
Get rid of the for loop on the read and change your printf() to be printf("%s\n",my_string1);