USB intterupt

[francescatodiego2]

Posted on May 31, 2005 at 11:27

USB intterupt

[francescatodiego2]

Posted on May 17, 2011 at 12:07

I am starting new project with USB interafce.

Fisrst step I have check all with ST sample and all work OK

Second step I have write mi own code and after first test I have some questions:

I start my application next I connect USB cable to PC.

I also store the UISTA value for the first interrupt only:

unsigned char flag = 0x00 ;

unsigned char tmp = 0xFF ;

USBIsr()

{

if (flag==0) {tmp = UISTA ; flag =1 }

....

}

Every 500ms I copy to SBUF the tmp value and I send to PC via serial port. (serial connection tested)

The read value is 0x00 !! Why the vector interrupt start if UISTA = 0 ?

thanks for help