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一、为何示波器上显示有两次chirp K而CATC却只抓到了一次chirp K信号
包1、2、3分别对应下图示波器抓到的1、2、3处的波形，3个包发送结束后主机再一次进行RESET，与device进行发送chirp K握手。
然而在示波器上显示两次chirp K信号，但是在CATC上却只抓到了B处的chirp K信号，
原因是在CATC只录取high speed信号的情况下，CATC以sof帧作为判断high speed条件，而在示波器上显示的第一次chirp K之前，
主机还没有向device发送sof从而CAT无法判断A处chirp K信号是否属于high speed信号，从而选择不记录第一个chirp K。
二、为何有两次chirp K信号
第一次chirp K信号是在suspend之后的，此时属于硬件枚举阶段，主机想要了解device的速度因而进行的reset，
而第二次的chirp K可由上图看到是在get device descriptor的3个包之后的，这个是根据不同的主机的行为，USB2.0规范并没有要求这里的复位动作，
复位是一个谨慎的动作，有的主机为了确保复位结束后设备处在一个已知的状态。C - how can i reset the USB Bus under linux? - Stack Overflow
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Daily--about 5 to 10 times--my USB camera disappears from the system. It's been happening from day 1 because the manufacturer driver is not compatible with Linux. lsusb and dmesg show it correctly at first, but after a longer period of time sometimes it disappears. The best solution to fix it is to reset the USB interface for that camera to get it back. I did it a few times manually using the C source code and it worked, but when I am doing it in a Bash loop it seems it's failing over and over. Any idea?
How can I make both programs work, so that I get my
/dev/video0 or 1 or 2 always available?
Step 1: Resetting the USB bus under Linux using this code:
/* few times it's resetting but when I use it in a Bash loop it's not doing it */
#include &stdio.h&
#include &usb.h&
int main(int argc, char *argv[]) {
struct usb_bus *
usb_init();
usb_find_busses();
usb_find_devices();
busses = usb_get_busses();
struct usb_bus *
for (bus = bus = bus-&next) {
struct usb_device *
usb_dev_handle *
for (dev = bus-& dev = dev-&next) {
char buf[1024];
junk = usb_open ( dev );
usb_get_string_simple(junk,2,buf,1023);
switch(argc) {
if ( junk == NULL ) {
printf("Can't open %p (%s)\n", dev, buf );
} else if (strcmp(buf,"HD Pro Webcam C920")==0) {
val = usb_reset(junk);
printf( "reset %p %d (%s)\n", dev, val, buf );
if ( junk == NULL ){
printf("Can't open %p (%s)\n", dev, buf );
val = usb_reset(junk);
printf( "reset %p %d (%s)\n", dev, val, buf );
usb_close(junk);
Step 2: Running as scanner - to make sure video0 or 1 or 2 is available, if not available resetting the USB bus
#!/bin/bash
for i in 0 1 2
tmp="/dev/video$i"
if [ -e $tmp ]
echo "/dev/video$i"
echo "NO - camera found - restarting the USB $i"
echo ROOT_PASSWORD_TO_EXECUTE | sudo -S /var/tmp/c-restartusb/restartusb
echo "Camera - logic ended, expecting the camera is available now"
Step 3: Still it's not available?
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
NO - camera found - restart the USB 2
NO - camera found - restart the USB 0
NO - camera found - restart the USB 1
8,44933148280
Don't sure your reset usb code right...
Can you find the usb device ?
If you can, try below:
BTW, This code is from . should be work if you can find the usb node:
/* usbreset -- send a USB port reset to a USB device */
#include &stdio.h&
#include &unistd.h&
#include &fcntl.h&
#include &errno.h&
#include &sys/ioctl.h&
#include &linux/usbdevice_fs.h&
int main(int argc, char **argv)
const char *
if (argc != 2) {
fprintf(stderr, "Usage: usbreset device-filename\n");
filename = argv[1];
fd = open(filename, O_WRONLY);
if (fd & 0) {
perror("Error opening output file");
printf("Resetting USB device %s\n", filename);
rc = ioctl(fd, USBDEVFS_RESET, 0);
if (rc & 0) {
perror("Error in ioctl");
printf("Reset successful\n");
close(fd);
If you can't, you maybe want to rescan to find the usb device like this:
echo 1 & /sys/dev/block/8:16/device/rescan
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Stack Overflow works best with JavaScript enabled当前位置:&&技术问答>
对于linux下的usb蓝牙适配器驱动hci_usb.c中的一些宏(如HCI_RESET)是什么意思？
&&&&来源:&互联网& 发布时间：
&&&&本文导语:&
以下这些宏是什么意思，有何用途？
#define HCI_IGNORE
#define HCI_RESET
#define HCI_DIGIANSWER
#define HCI_SNIFFER
#define HCI_BROKEN_ISOC
#define HCI_BCM9
应该和该driver对各个BT厂...
以下这些宏是什么意思，有何用途？
#define HCI_IGNORE
#define HCI_RESET
#define HCI_DIGIANSWER
#define HCI_SNIFFER
#define HCI_BROKEN_ISOC
#define HCI_BCM9
应该和该driver对各个BT厂家的usb dongle 所需要的特殊操作有关.
因为只要是BT的usb dongle,该driver就会支持(只要满足该id table),但是各个厂家的设备之间差别比较大,所以有些特殊操作而已.
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求翻译：usb mass storage reset delay 20sec是什么意思？
usb mass storage reset delay 20sec
问题补充：
USB大容量存储复位延迟20秒
usb大容量存储复位延迟20秒
usb大容量存储器重新设置延迟20sec
usb 大容量存储重置延迟 20 秒
usb 大量存储重置耽搁时间的 20sec
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