nRF5340 - custom USB SerialNumber

[Gabriele]

Hi,
running the USB hid sample project and sending from host terminal
$ journalctl -k -n 10
I get
[ 2231.751311] usb 1-1.3: SerialNumber: D0766E074450A9F0

I want to change the exposed SerialNumber to "2022070001"
How to do that ?
Looking around somewhere I've found a reference to NRF_FICR->DEVICEADDR[1:0].
Unfortunately, attempting to read this variable gets the compiler complaining NRF_FICR_Type has no member named DEVICEADDR.

What's the solution ?

[Kenneth]

Have you tried to use CONFIG_USB_DEVICE_SN:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.9.0/kconfig/CONFIG_USB_DEVICE_SN.html

Kenneth

[Gabriele]

Yes I did.

If I do not use CONFIG_USB_DEVICE_SN then I get
[ 2231.751311] usb 1-1.3: SerialNumber: D0766E074450A9F0

If I use CONFIG_USB_DEVICE_SN="2022070001" then I get
[ 2231.751311] usb 1-1.3: SerialNumber: 074450A9F0

The displayed string is the same, only it is truncated to the lenght of CONFIG_USB_DEVICE_SN

[Kenneth]

Looks like this only allocate a placeholder for the serial number string yes.

I don't see a way around this without modifying usb_descriptor.c in some way, you can either manipulate directly usb_fix_ascii_sn_string_descriptor(), but it may also look like the implementation of usb_update_sn_string_descriptor() is weak, which should mean that if you write a new usb_update_sn_string_descriptor() somewhere in your project that is included by include files at top of usb_descriptor.c/h, then it will fetch the serial number from there (instead of the default weak implementation you can find of usb_update_sn_string_descriptor() in usb_descriptor.c)

I can find that for instance the \connectivity_bridge\src\main.c does this by:

/* Overriding weak function to set iSerialNumber at runtime. */
uint8_t *usb_update_sn_string_descriptor(void)
{
    snprintk(usb_serial_str, sizeof(usb_serial_str), USB_SERIALNUMBER_TEMPLATE,
                (uint32_t)(NRF_FICR->DEVICEADDR[1] & 0x0000FFFF)|0x0000C000,
                (uint32_t)NRF_FICR->DEVICEADDR[0]);

    return usb_serial_str;
}

Best regards,
Kenneth

[Gabriele]

The compiler complains NRF_FICR_Type has no member named DEVICEADDR.
My target device is nRF5340.

[Kenneth]

Don't use usb_update_sn_string_descriptor() as-is, it was just as en example on how you can write your own usb_update_sn_string_descriptor() to set the usb_serial_str you want to use. Please remove code related to "FICR" from the usb_update_sn_string_descriptor(), it is not used in your case.

Kenneth

[Gabriele]

Ok. How to force usb_descriptor.c to use my override function without modifying usb_descriptor.c ? What's the trick ?