How to change the usb serial number

I am using "C:\Keil\ARM\Boards\Keil\MCB1700\RL\USB\Device\Memory", seems need to change "usb_lib.c"?

Thanks.

String descriptor structure on RAM

On RL-USB library, USBD_StringDescriptor structure, defined on usb_lib.c, gives the all string descriptors on the device, including the serial number string. As the default, this structure is assigned to ROM by "const" modifier. Deleting "const" modifier, this structure is placed on RAM, so that it can be modified at run time.

1) Copy C:\Keil\ARM\RV31\INC\usb_lib.c to your project folder, and rename it.
2) Change usb_lib.c reference in usb_config.c at the bottom of this file.

usb_config.c

#ifndef  __NO_USB_LIB_C
#include <usb_lib.c>    // <--- change to "renamed_usb_lib.c"
#endif

Now that you may customize renamed usb_lib.c as you like.

3) Near the bottom of usb_lib.c, USBD_StringDescriptor is defined.
Delete "const" from this definition.

usb_lib.c

__weak \ 
const struct {      // <--- delete "const" of this line
  struct {
    U8  len;
    U8  type;
    U16 langid;
  } desc_langid;
  USBD_STR_DEF(STRDESC_MAN);
  USBD_STR_DEF(STRDESC_PROD);
#if  (USBD_STRDESC_SER_ENABLE)
  USBD_STR_DEF(STRDESC_SER);
#endif
...
...
} USBD_StringDescriptor

4) At the start-up initialization in main(), before "usbd_connect(__TRUE);" is called,
the string descriptor for serial number is replaced to those read out from EEPROM.

USBD_StringDescriptor.descSTRDESC_SER.len (U8 variable) - length of custom string + 2
USBD_StringDescriptor.descSTRDESC_SER.str[] (U16 array) - body of custom string in UNICODE

Ah, you have to assign dummy string of enough length to USBD_STRDESC_SER

usb_config.c

#define USBD_STRDESC_SER            L"0001A0000000"  // <---  assign dummy string of enough length

USB_ReqGetDescriptor() routine may be overridden, but it isn't safe without original source code of this routine.

Tsuneo

Great! Thanks Tsuneo! Will try it now.

An interesting thing here is this part:

__weak \   <==== weak linkage, so another file can contain a symbol of same name to replace this.
const struct {
  struct {
    U8  len;
    U8  type;
    U16 langid;
  } desc_langid;

So in case this file contains lots of other things that a user do not want to change, then another source file should be able to redeclare USBD_StringDescriptor.

Aha, I know how how "__week" works.
But in this case, USBD_StringDescriptor definition uses bunch of #define macros and conditional compilation, which are defined in usb_lib.c and usb_config.c. To extract USBD_StringDescriptor definition, we have to make these macros referable. It's so troublesome. In this reason, above method is easier and safer, just to delete "const" modifier.

Tsuneo