USB HID does not use framing packets; instead the packetization inherent in the USBprotocol itself is used. The ability for the device to NAK Out transfers (until they can bereceived) provides the required flow control; the built-in CRC of each USB packetprovides the required error detection.13.4.3.1 Clock configurationThe KLx3 ROM supports the crystal-less USB feature. If the USB peripheral is enabled,then the ROM enables the 48-MHz HIRC. The ROM also enables the USB clockrecovery feature (by setting USB_CLK_RECOVER_CTRL[CLOCK_RECOVER_EN]to 1 and USB_CLK_RECOVER_IRC_EN[IRC_EN] to 1).13.4.3.2 Device descriptorThe Kinetis ROM configures the default USB VID/PID/Strings as below:Default VID/PID:• VID = 0x15A2• PID = 0x0073Default Strings:• Manufacturer [1] = "Freescale Semiconductor Inc."• Product [2] = "Kinetis Bootloader"You can customize the USB VID/PID/Strings with the Bootloader Configuration Area(BCA) of the flash. See Table 13-3. For example, the USB VID and PID can becustomized by writing the new VID to the usbVid(BCA + 0x14) field and the new PID tothe usbPid(BCA + 0x16) field of the BCA in flash. To change the USB strings, you needto prepare a structure (like the one shown below) in the flash, and then write the addressof the g_languages structure to the usbStringsPointer(BCA + 0x18) field of the BCA.g_languages = { USB_STR_0,sizeof(USB_STR_0),(uint_16)0x0409,(const uint_8 **)g_string_descriptors,g_string_desc_size};the USB_STR_0, g_string_descriptors and g_string_desc_size are defined as below.USB_STR_0[4] = {0x02,0x03,0x09,0x04};g_string_descriptors[4] ={ USB_STR_0,USB_STR_1,USB_STR_2,Peripherals SupportedKL27 Sub-Family Reference Manual , Rev. 5, 01/2016214 Freescale Semiconductor, Inc.
