# USB link to the board **URL:** \ **Category:** Legato Linux distribution (Yocto project)\ **Created:** [July 5, 2021, 1:09pm UTC](https://forum.legato.io/t/usb-link-to-the-board/5872 "2021-07-05T13:09:10Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![zuuuuk](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@zuuuuk](https://forum.legato.io/u/zuuuuk)\ **Post date:** [July 5, 2021, 1:09pm UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/1 "2021-07-05T13:09:10Z")
Hello. I use wp7502 + legato 20.04 how to understand that USB is connected? i want to see the USB cable is plugged in or unplugged. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [July 5, 2021, 3:42pm UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/2 "2021-07-05T15:42:14Z")
how about this? ```auto root@swi-mdm9x28-wp:/sys/bus/platform/drivers# cat /sys/devices/78d9000.usb/power_supply/usb/online 1 root@swi-mdm9x28-wp:/sys/bus/platform/drivers# cat /sys/devices/78d9000.usb/power_supply/usb/online 0 ``` ---
**Author:** ![zuuuuk](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@zuuuuk](https://forum.legato.io/u/zuuuuk)\ **Post date:** [July 6, 2021, 6:40am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/3 "2021-07-06T06:40:18Z")
When i connect through USB. root@swi-mdm9x15:~# ls /sys/devices/ -ls 0 drwxr-xr-x 3 root root 0 Jul 6 06:38 breakpoint 0 drwxr-xr-x 6 root root 0 Jan 1 1970 i2c-0 0 drwxr-xr-x 3 root root 0 Jul 6 06:38 msm\_def\_fab 0 drwxr-xr-x 3 root root 0 Jul 6 06:38 msm\_sys\_fab 0 drwxr-xr-x 136 root root 0 Jul 6 06:08 platform 0 drwxr-xr-x 3 root root 0 Jul 6 06:38 slimbus 0 drwxr-xr-x 3 root root 0 Jul 6 06:38 software 0 drwxr-xr-x 7 root root 0 Jul 1 10:23 system 0 drwxr-xr-x 3 root root 0 Jul 6 06:38 tracepoint 0 drwxr-xr-x 22 root root 0 Jul 6 06:08 virtual root@swi-mdm9x15:~# i not see usb. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [July 6, 2021, 6:48am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/5 "2021-07-06T06:48:55Z")
I am using wp76 … Can you have a search like find / -name “power\_supply” ---
**Author:** ![zuuuuk](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@zuuuuk](https://forum.legato.io/u/zuuuuk)\ **Post date:** [July 6, 2021, 7:21am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/6 "2021-07-06T07:21:48Z")
root@swi-mdm9x15:~# find / -name “power\_supply” /sys/devices/platform/msm\_otg/power\_supply /sys/class/power\_supply root@swi-mdm9x15:~# ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [July 6, 2021, 7:26am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/7 "2021-07-06T07:26:29Z")
does it work for this path? /sys/devices/platform/msm\_otg/power\_supply ---
**Author:** ![zuuuuk](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@zuuuuk](https://forum.legato.io/u/zuuuuk)\ **Post date:** [July 6, 2021, 7:31am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/8 "2021-07-06T07:31:01Z")
how to understand that USB is connected? root@swi-mdm9x15:/sys/devices/platform/msm\_otg/power\_supply/usb# ls -al drwxr-xr-x 3 root root 0 Jan 1 1970 . drwxr-xr-x 3 root root 0 Jan 1 1970 … -r–r–r-- 1 root root 4096 Jan 1 1970 current\_max lrwxrwxrwx 1 root root 0 Jan 1 1970 device → …/…/…/msm\_otg -r–r–r-- 1 root root 4096 Jan 1 1970 online drwxr-xr-x 2 root root 0 Jan 1 1970 power -r–r–r-- 1 root root 4096 Jan 1 1970 present -r–r–r-- 1 root root 4096 Jan 1 1970 scope lrwxrwxrwx 1 root root 0 Jan 1 1970 subsystem → …/…/…/…/…/class/power\_supply -r–r–r-- 1 root root 4096 Jan 1 1970 type -rw-r–r-- 1 root root 4096 Jan 1 1970 uevent ---
**Author:** ![zuuuuk](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@zuuuuk](https://forum.legato.io/u/zuuuuk)\ **Post date:** [July 6, 2021, 8:06am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/9 "2021-07-06T08:06:54Z")
alwase “0” root@swi-mdm9x15:/sys/devices/platform/msm\_otg/power\_supply/usb# cat online 0 1. even if I connect via usb i see “0” 2. even if i connect via GSM. whith out usb. i see “0” ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [July 6, 2021, 9:54am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/10 "2021-07-06T09:54:12Z")
I have just made a test with WP8548. // if USB is connected, /dev/usb\_link will be shown in “cat /sys/power/wake\_lock” root@fx30:~# cat /sys/power/wake\_lock /dev/usb\_link legato\_wakeup\_App\_wakeup\_app // if USB disconnect, /dev/usb\_link will not be shown in “cat /sys/power/wake\_lock” root@fx30:~# cat /sys/power/wake\_lock legato\_wakeup\_App\_wakeup\_app ```auto root@fx30:~# cm info Device: WP8548 IMEI: 359377060004735 IMEISV: 2F FSN: LL537500110203 Firmware Version: SWI9X15Y_07.13.07.00 92cfd2c jenkins 2018/08/22 19:18:52 Bootloader Version: SWI9X15Y_07.13.07.00 92cfd2c jenk[801.199297] qup_i2c qup_i2c.0: QUP: I2C status flags :0x1363c8, irq:187 ins 2018/08/22 19:18:39 [801.211750] qup_i2c qup_i2c.0: I2C slave addr:0x3a not connected MCU Version: 002.004 PRI Part Number (PN): 9904889 PRI Revision: 01.11 Carrier PRI Name: ATT Carrier PRI Revision: 001.036_000 SKU: 1102621 Last Reset Cause: Unknown Resets Count: Expected: 0 Unexpected: 0 root@fx30:~# ``` ---
**Author:** ![zuuuuk](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@zuuuuk](https://forum.legato.io/u/zuuuuk)\ **Post date:** [July 6, 2021, 10:20am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/11 "2021-07-06T10:20:40Z")
Ok. path /sys/power/wake\_lock it work ---
**Author:** ![zuuuuk](https://avatars.discourse-cdn.com/v4/letter/z/e5b9ba/32.png) [@zuuuuk](https://forum.legato.io/u/zuuuuk)\ **Post date:** [July 6, 2021, 10:42am UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/12 "2021-07-06T10:42:11Z")
Small question. On one of my devices, I read the log **root@swi-mdm9x15:/sys/power# cat wake\_unlock** /dev/usb\_link qcsi qmuxd\_port\_wl\_0 qmuxd\_port\_wl\_1 qmuxd\_port\_wl\_2 qmuxd\_port\_wl\_3 qmuxd\_port\_wl\_4 qmuxd\_port\_wl\_5 qmuxd\_port\_wl\_6 qmuxd\_port\_wl\_7 Why so much **qmuxd\_port\_wl\_X**? for some reason in this file the path **/dev/usb\_link**? Is there something wrong? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\ **Post date:** [July 6, 2021, 12:50pm UTC](https://forum.legato.io/t/usb-link-to-the-board/5872/13 "2021-07-06T12:50:05Z")
I don’t see this on my wp8548, how to reproduce? Btw, you should use “cat wake\_lock”