# \[WP76xx\]\[HW\] Switch USB host or USB function **URL:** \ **Category:** Legato Linux distribution (Yocto project)\ **Created:** [December 3, 2019, 6:52am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887 "2019-12-03T06:52:17Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![HIROKI11976](https://avatars.discourse-cdn.com/v4/letter/h/a9adbd/32.png) [@HIROKI11976](https://forum.legato.io/u/HIROKI11976)\ **Post date:** [December 3, 2019, 6:52am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/1 "2019-12-03T06:52:17Z")
[WP76xx\_switch\_USBHost\_function.xlsx](https://forum.legato.io/uploads/short-url/obogiv3KgutrROuPvyltF34pfNy.xlsx) (39.9 KB) Back Ground: We would like to switch the function that WP76xx was operated as USB host or USB function. In order to support it, we make the attached block diagram. - How to switch: control GPIO22 and GPIO23, and supply to power SW IC to supply Micro USB IF - How to recognize function: Check the logic via USB\_ID or GPIO25 Question: Please check the attached file as “WP76xx\_switch\_USBHost\_function.xlsx”. Can this block diagram support to switch either USB Host or USB Function? Best Regards, ---
**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:** [December 3, 2019, 8:08am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/2 "2019-12-03T08:08:24Z")
for hardware topic, please directly contact Sierra FAE. ---
**Author:** ![JordanZhao](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jordanzhao/32/789_2.png) [@JordanZhao](https://forum.legato.io/u/JordanZhao)\ **Post date:** [December 5, 2019, 4:09am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/3 "2019-12-05T04:09:24Z")
Are we talking about USB OTG? ---
**Author:** ![HIROKI11976](https://avatars.discourse-cdn.com/v4/letter/h/a9adbd/32.png) [@HIROKI11976](https://forum.legato.io/u/HIROKI11976)\ **Post date:** [December 9, 2019, 1:29am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/4 "2019-12-09T01:29:08Z")
Hi, Jordan > > Are we talking about USB OTG? No, I talked the following behavior that; - USB Host: WP76xx supply voltage to external USB device - USB function: No supply voltage, only receiving data via USB ---
**Author:** ![JordanZhao](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jordanzhao/32/789_2.png) [@JordanZhao](https://forum.legato.io/u/JordanZhao)\ **Post date:** [December 9, 2019, 7:45am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/5 "2019-12-09T07:45:52Z")
OK, I see. Then it needs a help from the HW team. ---
**Author:** ![tgoto](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/tgoto/32/823_2.png) [@tgoto](https://forum.legato.io/u/tgoto)\ **Post date:** [December 10, 2019, 6:01am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/6 "2019-12-10T06:01:29Z")
Hi Hiroki, Please make SFDC ticket for this. ---
**Author:** ![HIROKI11976](https://avatars.discourse-cdn.com/v4/letter/h/a9adbd/32.png) [@HIROKI11976](https://forum.legato.io/u/HIROKI11976)\ **Post date:** [December 23, 2019, 6:22am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/7 "2019-12-23T06:22:59Z")
Hi, Sierra Team As we talked with customer, they consider to switch USB function or Host as I said. In that case, they consider that is judged USB function or USB Host by trigger the logic of USB\_ID. - USB\_ID: “H” or Open —\> WP760x=USB Host (Supply USB\_VBUS to external USB device) - USB\_ID: “L” —\> WP760x=USB function (Receive USB\_VBUS from external USB device) Question: Do you have the way how to monitor the logic of USB\_ID either “H” or “L” in legato App or Linux command? (Sorry I could not find [legato.io](http://legato.io).) ---
**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:** [December 23, 2019, 7:42am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/8 "2019-12-23T07:42:22Z")
do you know what device will be plugged to the USB? If yes, you can check “cat /sys/kernel/debug/usb/devices” for the device name. ---
**Author:** ![HIROKI11976](https://avatars.discourse-cdn.com/v4/letter/h/a9adbd/32.png) [@HIROKI11976](https://forum.legato.io/u/HIROKI11976)\ **Post date:** [December 23, 2019, 9:33am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/9 "2019-12-23T09:33:42Z")
> > do you know what device will be plugged to the USB? No, I could not confirm device name. I consider the following sequence to switch USB host/function. [1] Monitor USB\_ID “H” or “L”, instead of GPIO (Because our system is insufficient GPIO IF.) [2] If USB\_ID=“H”, WP76xx set to be worked as USB function [3] If USB\_ID=“L”, WP76xx set to be worked as USB Host In order to fulfill [1], I would like to know whether USB\_ID can be monitored either “H” logic or “L” logic under legato or yocto framework. ---
**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:** [December 23, 2019, 9:57am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/10 "2019-12-23T09:57:28Z")
how about checking the kernel log? I saw that in case of USB host, when client connected, you should see this message in dmesg: “New USB device found”. ---
**Author:** ![HIROKI11976](https://avatars.discourse-cdn.com/v4/letter/h/a9adbd/32.png) [@HIROKI11976](https://forum.legato.io/u/HIROKI11976)\ **Post date:** [December 23, 2019, 11:36pm UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/11 "2019-12-23T23:36:53Z")
> > how about checking the kernel log? Thanks for your advise, but it could not be applied in our system. Because I consider that WP76xx will be switch either USB Host or USB Function before external USB device is jack-in. So I consider the way to switch USB Host/Function, and I assume that switching USB can be monitored USB\_ID logic. That’s why, I asked it. ---
**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:** [December 24, 2019, 1:15am UTC](https://forum.legato.io/t/wp76xx-hw-switch-usb-host-or-usb-function/4887/12 "2019-12-24T01:15:31Z")
Please contact Sierra FAE as this is more likely to be hardware stuff.