libusb driver question: can't write to endpoint

So I sat down to start seeing if I could write the aforementioned driver for
the Logitech Harmony remote using libusb. After reading the docs, I whipped
out the following test code (ok, its mostly a copy and paste of the docs,
but that's OK) which binds to the interface and attempts to do an interrupt
transfer to the endpoint.

But I get: "error submitting URB: Bad address". I've attached the (very
ugly) code below, but I don't think it's a coding error as much as a not
understanding error.

Looking at lsusb, the device has one Configuration with bConfigurationValue
1, and one Interface with bInterfaceNumber 0.

Under this interface, it has two endpoints, 0x81, "EP 1 IN", and 0x02, "EP 1
OUT", which I believe, from looking at USB Snoopy dumps, are IN ==>
device-to-host, and OUT ==> host-to-device. But I've tried my code using
both endpoints, and get the same error each time.

The USBSnoopy log shows from windows shows a very simple setup:
SELECT_CONFIGURATION, CLASS_INTERFACE, GET_DESCRIPTOR_FROM_INTERFACE, and
then a ton of BULK_OR_INTERRUPT_TRANSFERs. lsusb shows that the devices or
of transfer type Interrupt.

Since all the software does is write a blob to the remote (which, after
looking, turns out to just be XML), this all seems straight forward. It
doesn't seem like I have to do any special setup...

The USBSnoopy logs show it writing 64 bytes at a time, so that's what I
write in my code.

-- 
Phil Dibowitz                             [email protected]
Open Source software and tech docs        Insanity Palace of Metallica
http://www.phildev.net/                   http://www.ipom.com/

"Never write it in C if you can do it in 'awk';
 Never do it in 'awk' if 'sed' can handle it;
 Never use 'sed' when 'tr' can do the job;
 Never invoke 'tr' when 'cat' is sufficient;
 Avoid using 'cat' whenever possible" -- Taylor's Laws of Programming

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#include <stdio.h>
#include <errno.h>
#include <stdio.h>
#include <usb.h>

#define LH_VENDOR_ID 0x046d
#define LH_PRODUCT_ID 0xc110
#define DATAFILE "/tmp/Connectivity.EZHex"
#define SIZE 64
#define IN_EP 0x81
#define OUT_EP 0x02

void write_data(usb_dev_handle *udev);

int main(int argc, char *argv[])
{
	struct usb_bus *busses, *bus;
	int retval = 0;
    
	usb_init();
	usb_find_busses();
	usb_find_devices();
    
	busses = usb_get_busses();

	/* loop through busses... */
	for (bus = busses; bus; bus = bus->next) {
		struct usb_device *dev;

		/* loop through devices on bus ...*/
		for (dev = bus->devices; dev; dev = dev->next) {
			usb_dev_handle *udev;
			if (dev->descriptor.idVendor == LH_VENDOR_ID
			    && dev->descriptor.idProduct == LH_PRODUCT_ID) {
				printf("Found remote\n");
				udev = usb_open(dev);
				if (!udev) {
					printf("Failed to open device\n");
					exit(1);
				}
				printf("Opened device\n");
				/*
 				 * Choose the first configuration (1)
 				 */
				if (usb_set_configuration(udev,1) < 0) {
					printf("Failed to set conf: %s\n",
						usb_strerror());
					exit(1);
				}
				printf("Set conf\n");
				/*
 				 * Choose the first interface (0)
 				 */
				retval = usb_claim_interface(udev,1);
				if (retval == -EBUSY) {
					printf("Interface busy\n");
					exit(1);
				}
				printf("Claimed device\n");
				write_data(udev);
				usb_release_interface(udev,0);
				printf("released device\n");
				usb_close(udev);
				printf("closed device\n");
				exit(0);
			} else {
				printf("Found another device\n");
				continue;
			}
		}
	}
	exit(1);
}

void write_data(usb_dev_handle* udev)
{
	printf("writing data...\n");
	char buf[SIZE];
	int bytes = 0;
	FILE *fh;
	fh = fopen(DATAFILE, "r");
	int i = 0;
	while (bytes = read((int)fh, buf, SIZE)) {
		printf("writing %d bytes (%d)\n",SIZE,++i);
		if (usb_interrupt_write(udev, OUT_EP, buf, bytes, 2) < 0) {
			printf("Write failed: %s\n", usb_strerror());
			return;
		}
	}
	fclose(fh);
}

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