I download the offical USB keyboard program into this arm AT91SAM7SE512. when the device powered on,the os of WIN XP need a ACK at the SET_IDLE process, but the device don't send this ACK packet.WHY? After, windows cancel the device.

if I use external DC power supply, I relink the usb cable, the device can work normally.

Thank you ! 谢谢！

first link:
.....
32.0 CTL 00 09 01 00 00 00 00 00 SET CONFIG 22.1.0
32.0 CTL 21 0a 00 00 00 00 00 00 SET IDLE 23.1.0
32.0 USTS 00 00 01 c0 canceled 23.2.0
32.0 CTL 81 06 00 22 00 00 7d 00 GET DESCRIPTOR 24.1.0
32.0 USTS 0c 00 00 c0 buffer overrun 24.2.0
32.0 CTL 81 06 00 22 00 00 7d 00 GET DESCRIPTOR 25.1.0(2)
32.0 USTS 05 00 00 c0 no response 25.2.0
15.0 CTL 23 01 01 00 02 00 00 00 CLEAR FEATURE 27.1.0
15.0 CTL a3 00 00 00 02 00 04 00 GET STATUS 28.1.0
15.0 DI 01 01 02 00 .... 28.2.0
15.0 CTL 23 01 11 00 02 00 00 00 CLEAR FEATURE 29.1.0

link usb cable again:
......
32.0 CTL 00 09 01 00 00 00 00 00 SET CONFIG 37.1.0
32.0 CTL 21 0a 00 00 00 00 00 00 SET IDLE 38.1.0
32.0 CTL 81 06 00 22 00 00 7d 00 GET DESCRIPTOR 39.1.0
32.0 DI 05 01 09 06 a1 01 75 01 95 08 05 07 19 e0 29 e7 15 00 25 01 81 02 95 03 75 08 15 00 25 53 05 07 ......u.......). 39.2.0
32.2 DO 01 . 40.1.0