Media Transfer Protocol

The Media Transfer Protocol (MTP) allows you to transfer files to and from your Windows 10 IoT Core device through USB. It allows access to the device's internal storage and the SD card, if present.

The feature is part of the IoT Core Kits, which can be downloaded and installed from the Windows 10 IoT Core Packages.

How to install the MTP feature on a device running Windows 10 IoT Core

Provisioning the device with required packages

1. Launch PowerShell or SSH and access your device running Windows 10 IoT Core.
2. From PowerShell or SSH, do the following:
   1. Create a temporary folder on the target machine (e.g. C:\MTPTemp).
   2. Based on your device's architecture, copy the following packages from your PC (C:\Program Files (x86)\Windows Kits\10\MSPackages\Retail\<arch>\fre) to C:\MTPTemp:
      • Microsoft-OneCoreUAP-Mtp-UserService-Package.cab
      • Microsoft-OneCoreUAP-Mtp-UserService-Package_Lang_en-US.cab
      • Microsoft-WindowsStorSvc-API-Schema-Extension-Package.cab
      • Microsoft-WindowsStorSvc-API-Schema-Extension-Package_Lang_en-US.cab
   3. Run these commands from C:\MTPTemp to install the packages to your IoT device's system image:
      • ApplyUpdate.exe -stage Microsoft-OneCoreUAP-Mtp-UserService-Package.cab
      • ApplyUpdate.exe -stage Microsoft-OneCoreUAP-Mtp-UserService-Package_Lang_en-US.cab
      • ApplyUpdate.exe -stage Microsoft-WindowsStorSvc-API-Schema-Extension-Package.cab
      • ApplyUpdate.exe -stage Microsoft-WindowsStorSvc-API-Schema-Extension-Package_Lang_en-US.cab
      • ApplyUpdate.exe -commit
3. The device will boot to the Update OS, install the MTP feature, and reboot to the MainOS.

Enabling the MTP USB interface

Once the device comes back to the MainOS, the USBFN configuration still needs to be updated to include MTP. In order to do that, you will need to add MTP to the interfaces enumerated by USBFN. The USB registry settings article explains the details of USB's configuration.

While you can modify the default USBFN configuration available under the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN\Configurations\Default key, it is recommended to define your own, as they will not get overwritten by system updates.

Creating a new USBFN configuration with the MTP interface

Follow these steps to add a new configuration with MTP:

1. Add a new key under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN\Configurations. Example: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN\Configurations\MyConfiguration.
2. Under the new key, create a REG_MULTI_SZ value InterfaceList equal to MTP.
3. Under the same key, create a REG_BINARY value MSOSCompatIdDescriptor equal to 2800000000010400010000000000000000014D545000000000000000000000000000000000000000.
4. Under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN add a new REG_SZ value CurrentConfiguration equal to the name of the newly created key. In this case, it would be MyConfiguration.
5. [Optional] Under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN add a new REG_DWORD value IncludeDefaultCfg equal to 1. This will make the USB driver enumerate the default interfaces along with MTP.

Adding the MTP interface to an existing configuration

Follow these steps to add MTP to an existing USBFN configuration:

1. Find the current configuration by checking the CurrentConfiguration value under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN. If the value is present, then the current configuration can be found under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN\Configurations\[CurrentConfiguration]. Otherwise it is under HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\USBFN\Configurations\Default.
2. Under the current configuration key, add \0MTP to the value of InterfaceList. The \0 part is used as the type of InterfaceList is REG_MULTI_SZ and it requires this separator between values.
3. Modify the MSOSCompatIdDescriptor value to include the MTP's descriptor. In order to create a valid descriptor containing all interfaces currently under the InterfaceList value, please follow the instructions documentation available at the bottom of this page. OS_Desc_CompatID.doc gives an explanation of the descriptor's format and an example of including multiple interfaces in the descriptor. MTP's compatible and subcompatible IDs are also available on the same page and are used in one of the examples.

How to include MTP in Your Custom FFU

1. Add IOT_MTP feature ID to the OEM Input file. This is an equivalent of following the steps from the "Provisioning the device with required packages" section.
2. Make sure to apply the same registry changes as mentioned in the "Creating a new USBFN configuration with the MTP interface" section. Follow these instructions to learn how to apply registry changes to an FFU.
3. Create the image\FFU. Read this article for instructions.

How to set up the MTP SD card filter

By default MTP will enumerate all of the contents of an SD card, if it is present on the device. It is possible, however, to limit this enumeration to a specific subfolder. In order to do so, you must add a registry value MTPSDFolderFilter under the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\MTP. The value is of type REG_SZ and should contain a relative path to the folder you would like MTP to enumerate. The folder will get automatically created if it does not already exist.

Sample paths:

• \FirstLevelDirectory;
• FirstLevelDirectory;
• \FirstLevelDirectory\SecondLevelDirectory;
• Never\Before\Created\Directory.

See this link for details about customizing your image with specific registry entries.