I do not know the solution for my problem. I need to emulate a USB keyboard. So far, nothing complex. BUT: It is supposed to be a USB 1.1 keyboard! I know that
UDCON = (1 << LSM)
should be used. But that alone does not make the trick. The USB Device (By the way: it is an Arduino Leonardo) is not found, anyway.
Post the code of what you have written and we could try and see where you are going wrong.
Read how to use this forum to find out how to do this correctly.
What is USB slow mode, that is not one of the official modes of the USB specification.
21.8 Speed Control
The speed selection (Full Speed or Low Speed) depends on the D+/D- pull-up. The LSM bit in UDCON register allows to select an internal pull up on D- (Low Speed mode) or D+ (Full Speed mode) data lines.
You won't get much help here with that attitude. Provide the necessary information or help yourself.
The "magic" is to switch to the Leonardo from USB 2.0 to 1.1.
Explain why this is necessary. The keyboard class usually works, if it doesn't for you, tell us what you're connecting to and why it doesn't work in default mode. Maybe you're wrong that the problem is in the USB speed mode?