wouldn't it make more sense to call it like this:

[pascal]
Buf[0] := $52; // With or without doesn't matter, got it from wiili.org
Buf[1] := $11; // Port
Buf[2] := $F0; // all leds on and rumbler off?

if not FHidDevice.SetOutputReport(Buf, 3) then //<- 3 bytes?
Log('Not set player led');
[/pascal]

edited to $F0 instead of $0F