Hi Mehdi,

SEND_REQUESTED_DESCRIPTOR must be called
after SetUp packet detection and validation, and
before Control-IN interrupt.
Until SEND_REQUESTED_DESCRIPTOR fills the Control-IN buffer with the first part of the device descriptor, Control-IN interrupt doesn't occur.
Call it in the mainloop.

Modify your code as follows
- Make two flags, FLAG_USB_TRANSMIT and FLAG_CTRL_IN
- Clear these flags in initialization

In the ISR,
- Set both flags after the validation in CONTROL_OUT_INTERRUPT
- Set FLAG_CTRL_IN in CONTROL_IN_INTERRUPT
- Delete "CALL SEND_REQUESTED_DESCRIPTOR" in CONTROL_IN_INTERRUPT. It is moved to the mainloop.

In the mainloop,
- If both of FLAG_USB_TRANSMIT and FLAG_CTRL_IN are set, call SEND_REQUESTED_DESCRIPTOR
- Clear FLAG_CTRL_IN after calling SEND_REQUESTED_DESCRIPTOR

In SEND_REQUESTED_DESCRIPTOR routine,
- Clear FLAG_USB_TRANSMIT when the last packet is written to the Control-IN buffer.

Tsuneo