Product ID Problem

[Henning]

Hi there,

In linux i get a product ID of "fd13" :

lsusb: Bus 001 Device 006: ID 04b4:fd13

Which is in dezimal "64787".
The return value of "Usb_Device.getDescriptor().getIdVendor()" is defined as
"public short getIdProduct()"

So the return value is  "-749" It seems short is to short..

Is there another way to get the correct value? Utils.logbus(bus) does it print correct - but there is no way to get it.

Some hints?

Thanx,

Hs

[andi]

Java only knows signed values and will expand short to int. So if the first bit is the this will give a negative number when expanded to int. Just mask the short with & 0xffff if you want to get the unsigned value. Execute the following example to see what I mean:

short vendorId = (short) 0xfd13; // without the short cast the value 0xfd13 would already expand to int and give a compile error
System.out.println("signed short: " + vendorId);
int vendorIdInt = vendorId;
System.out.println("signed int: " + vendorIdInt);
System.out.println("signed int (hex): " + Integer.toHexString(vendorId));
System.out.println("unsigned short: " + (vendorId & 0xffff));
System.out.println("unsigned int: " + (vendorIdInt & 0xffff));
vendorIdInt = vendorId & 0xffff; // mask to unsigned int
System.out.println("unsigned int: " + vendorIdInt);
System.out.println("unsigned int (hex): " + Integer.toHexString(vendorIdInt));

signed short: -749
signed int: -749
signed int (hex): fffffd13
unsigned short: 64787
unsigned int: 64787
unsigned int: 64787
unsigned int (hex): fd13

Also have a look at the second paragraph in this post https://sourceforge.net/forum/message.php?msg_id=4255720