# Failure to enumerate USB

**URL:** <https://forum.legato.io/t/failure-to-enumerate-usb/6943>\
**Category:** Legato Linux distribution (Yocto project)\
**Created:** [August 23, 2025, 11:03pm UTC](https://forum.legato.io/t/failure-to-enumerate-usb/6943 "2025-08-23T23:03:45Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jack.heaffey](https://avatars.discourse-cdn.com/v4/letter/j/ad7895/32.png) [@jack.heaffey](https://forum.legato.io/u/jack.heaffey)\
**Post date:** [August 23, 2025, 11:03pm UTC](https://forum.legato.io/t/failure-to-enumerate-usb/6943/1 "2025-08-23T23:03:45Z")

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Hi,

I develop a device where a WP76xx cell module is a USB CDC device and a separate processor is the USB host.

There are times when the USB host must disable the USB connection and restart the connection frequently, roughly every 10 seconds or so. When restarting the USB connection every 10 seconds, after a few hours the WP76xx module stops responding to USB requests from the host and the USB enumeration process fails, even after several attempts, until the WP76xx module is restarted.

I wonder if this is due to a bug in the gadget USB driver. I’m currently using firmware R16.1 and I cannot migrate to R17 because it doesn’t support WP7610 modules.

I do build a custom yocto image and so can patch the kernel if needed.

My ideal response to this post would be “ah yes, that issue was resolved in R17 by commit xxxxxx”, which I could then backport to the R16.1 kernel.

Does the above issue ring any bells? If not, is there a way to reset the gadget USB controller, eg unloading the gadget serial driver and reloading it?

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**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:** [August 24, 2025, 1:43am UTC](https://forum.legato.io/t/failure-to-enumerate-usb/6943/2 "2025-08-24T01:43:54Z")

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Are you able to route the usb port to linux pc and see if you can reproduce the issue?

Or you can connect the mango board to your host mcu and see if there is any problem.

This can understand if this is hardware issue.

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<div class="post-metadata">

**Author:** ![jack.heaffey](https://avatars.discourse-cdn.com/v4/letter/j/ad7895/32.png) [@jack.heaffey](https://forum.legato.io/u/jack.heaffey)\
**Post date:** [August 26, 2025, 9:31am UTC](https://forum.legato.io/t/failure-to-enumerate-usb/6943/3 "2025-08-26T09:31:26Z")

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Sadly I cannot route the USB port to a Linux PC or mango board.

I have observed this issue on two devices, so it’s not specific to one device.

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<div class="post-metadata">

**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:** [August 26, 2025, 9:45am UTC](https://forum.legato.io/t/failure-to-enumerate-usb/6943/4 "2025-08-26T09:45:01Z")

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i mean to connect the mangoh USB to host processor, not routing the USB of your device to mangoh board.