# Customised USB OTG composite - usb serial

**URL:** <https://forum.legato.io/t/customised-usb-otg-composite-usb-serial/2407>\
**Category:** Uncategorized\
**Created:** [April 4, 2017, 7:07pm UTC](https://forum.legato.io/t/customised-usb-otg-composite-usb-serial/2407 "2017-04-04T19:07:08Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![johnofleek](https://avatars.discourse-cdn.com/v4/letter/j/e9bcb4/32.png) [@johnofleek](https://forum.legato.io/u/johnofleek)\
**Post date:** [April 4, 2017, 7:07pm UTC](https://forum.legato.io/t/customised-usb-otg-composite-usb-serial/2407/1 "2017-04-04T19:07:08Z")

</div>

Hi

I have a project which needs a USB serial port.

I used method [http://legato.io/legato-docs/latest/howToCustomizeUSB.html](http://legato.io/legato-docs/latest/howToCustomizeUSB.html) → “Customize Endpoints” section

to create a file /etc/legato/usbmode with contents:

> ecm  
> acm  
> serial

This creates

 ![](https://us1.discourse-cdn.com/flex019/uploads/legato1/original/1X/f3b6e12ddfecf26a78416befd6a3ce0d11e4fd13.png)

Which is great.

The problem is that when the WP85 OTG is plugged into a windows machine - I get error 10 in device manager.  
If the WP85 has a standard USB configuration it works fine with the same windows machine  
I’m guessing that the SW driver only works with the standard WP85 configuration?  
Any ideas how to get a driver to work with the new WP85 configuration?

Thanks in advance

John

---

<div class="post-metadata">

**Author:** ![daav](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/daav/32/64_2.png) [@daav](https://forum.legato.io/u/daav)\
**Post date:** [April 6, 2017, 6:02am UTC](https://forum.legato.io/t/customised-usb-otg-composite-usb-serial/2407/2 "2017-04-06T06:02:24Z")

</div>

Hi @johnofleek

Unfortunately, it appears that the Windows driver is only compatible with the compositions you can setup with AT!USBCOMP command.  
Other customizations are fine for a Linux host, but not for a Windows one (will ensure that this limitation is mentioned in the documentation).

---

<div class="post-metadata">

**Author:** ![johnofleek](https://avatars.discourse-cdn.com/v4/letter/j/e9bcb4/32.png) [@johnofleek](https://forum.legato.io/u/johnofleek)\
**Post date:** [April 6, 2017, 9:40am UTC](https://forum.legato.io/t/customised-usb-otg-composite-usb-serial/2407/3 "2017-04-06T09:40:55Z")

</div>

Hi David

Many thanks for the clarification - it’s a shame that serial isn’t available in the standard composition options.  
To aid my memory in the future for the WP85 Legato 16.10.1 the following is the standard response to

at!entercnd="A710  
AT!USBCOMP=?

> AT!USBCOMP=,,  
> - configuration index to which the composition applies, should be 1

> - 1:Generic

> - DIAG - 0x00000001,  
> NMEA - 0x00000004,  
> MODEM - 0x00000008,  
> AT - 0x00000010,  
> OSA - 0x00000020,  
> RAWDATA - 0x00000040,  
> RMNET0 - 0x00000100,  
> RMNET1 - 0x00000400,  
> MBIM - 0x00001000,  
> RNDIS - 0x00004000,  
> AUDIO - 0x00010000,  
> ECM - 0x00080000,  
> e.g.  
> 10D - diag, nmea, modem, rmnet interfaces enabled  
> 1009 - diag, modem, mbim interfaces enabled

> OK

> Config Index: 1  
> Config Type: 1 (Generic)  
> Interface bitmask: 0008015D (diag,nmea,modem,at,rawdata,rmnet0,ecm)

And

AT!USBCOMP?

> Config Index: 1  
> Config Type: 1 (Generic)  
> Interface bitmask: 0008015D (diag,nmea,modem,at,rawdata,rmnet0,ecm)