Compiles and runs... but no data?

usbscale.c

@@ -6,15 +6,91 @@
 
 #define DEBUG 1
 
-static void print_devs(libusb_device **devs)
+static libusb_device* find_scale(libusb_device**);
+
+int main(void)
 {
+	libusb_device **devs;
+	int r;
+	ssize_t cnt;
+	libusb_device* dev;
+	libusb_device_handle* handle;
+
+	r = libusb_init(NULL);
+	if (r < 0)
+		return r;
+
+	/*
+	 * Get a list of USB devices
+	 */
+	cnt = libusb_get_device_list(NULL, &devs);
+	if (cnt < 0)
+		return (int) cnt;
+
+	/*
+	 * Look for a scale amongst the USB devices
+	 */
+	dev = find_scale(devs);
 	
+	/*
+	 * Open a handle to this found scale
+	 */
+	libusb_open(dev, &handle);
+#ifdef __linux__
+	libusb_detach_kernel_driver(handle, 0);
+#endif
+	libusb_claim_interface(handle, 0);
+
+	/*
+	 * Try to transfer data about status
+	 *
+	 * http://www.beyondlogic.org/usbnutshell/usb6.shtml 
+	 */
+	unsigned char blah[8];
+	libusb_control_transfer(
+		handle,
+		LIBUSB_ENDPOINT_IN | LIBUSB_REQUEST_TYPE_CLASS |
+		    LIBUSB_RECIPIENT_INTERFACE,
+		//bmRequestType => direction: in, type: class,
+		        //    recipient: interface
+		0x01,   //bRequest => HID get report
+		0x0300, //wValue => feature report
+		0x00,   //windex => interface 0
+		blah,
+		8,    //wLength
+		1000 //timeout => 1 sec
+		);
+	int i;
+	for(i = 0; i < 8; i++) {
+		printf("%x\n", blah[i]);
+	}
+	
+
+	/*
+	 * Free the device handle, device list and other cleanup
+	 * tasks
+	 */
+#ifdef __linux__
+	libusb_attach_kernel_driver(handle, 0);
+#endif
+	libusb_close(handle);
+	libusb_free_device_list(devs, 1);
+	libusb_exit(NULL);
+	return 0;
+}
+
+static libusb_device* find_scale(libusb_device **devs)
+{
 	if(DEBUG)
-		libusb_set_debug(null, 3);
+		libusb_set_debug(NULL, 3);
 
-	libusb_device *dev;
 	int i = 0;
+	libusb_device* dev;
 
+	/*
+	 * Loop through each usb device, and for each device, loop through the
+	 * scales list to see if it's one of our listed scales
+	 */
 	while ((dev = devs[i++]) != NULL) {
 		struct libusb_device_descriptor desc;
 		int r = libusb_get_device_descriptor(dev, &desc);
@@ -26,49 +102,39 @@ static void print_devs(libusb_device **devs)
         for (i = 0; i < scalesc; i++) {
             if(desc.idVendor  == scales[i][0] && 
                desc.idProduct == scales[i][1]) {
-				if(DEBUG) {
+				/*
-					printf("Found scale %04x:%04x (bus %d, device %d)\n",
+				 * Debugging data about found scale
-                    desc.idVendor, desc.idProduct,
+				 */
-                    libusb_get_bus_number(dev), libusb_get_device_address(dev));
+#ifdef DEBUG
+
+				printf("Found scale %04x:%04x (bus %d, device %d)\n",
+						desc.idVendor,
+						desc.idProduct,
+						libusb_get_bus_number(dev),
+						libusb_get_device_address(dev));
 
 					printf("It has descriptors:\n\tmanufc: %d\n\tprodct: %d\n\tserial: %d\n",
 							desc.iManufacturer,
 							desc.iProduct,
 							desc.iSerialNumber);
-				}
-                unsigned char string[256];
 
-                libusb_device_handle* hand;
+					/*
+					 * A char buffer to pull string descriptors in from the device
+					 */
+					unsigned char string[256];
+					libusb_device_handle* hand;
+					libusb_open(dev, &hand);
 
-                libusb_open(dev, &hand);
+					r = libusb_get_string_descriptor_ascii(hand, desc.iManufacturer,
-
+							string, 256);
-                r = libusb_get_string_descriptor_ascii(hand, desc.iManufacturer,
+					printf("Manufacturer: %s\n", string);
-                        string, 256);
+					libusb_close(hand);
-                printf("Manufacturer: %s\n", string);
+#endif
+					return dev;
+					
                 break;
             }
         }
 	}
 }
 
-int main(void)
-{
-	libusb_device **devs;
-	int r;
-	ssize_t cnt;
-
-	r = libusb_init(NULL);
-	if (r < 0)
-		return r;
-
-	cnt = libusb_get_device_list(NULL, &devs);
-	if (cnt < 0)
-		return (int) cnt;
-
-	print_devs(devs);
-	libusb_free_device_list(devs, 1);
-
-	libusb_exit(NULL);
-	return 0;
-}
-