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samples: subsys: usb: mtp: add new sample
Add a sample application that demonstrates how to use the new USB MTP device class. This shows how to set up the device tree to expose storage partitions to a host over USB using MTP. Files/Dirs can be accessed from host without host supportfor the underlying filesystem like littlefs. Signed-off-by: Mohamed ElShahawi <[email protected]>
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‎samples/subsys/usb/mtp/CMakeLists.txt

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# SPDX-License-Identifier: Apache-2.0
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cmake_minimum_required(VERSION 3.20.0)
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find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
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project(mtp)
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include(${ZEPHYR_BASE}/samples/subsys/usb/common/common.cmake)
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FILE(GLOB app_sources src/*.c)
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target_sources(app PRIVATE ${app_sources})

‎samples/subsys/usb/mtp/Kconfig

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# Copyright (c) 2023 Nordic Semiconductor ASA
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# SPDX-License-Identifier: Apache-2.0
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# Source common USB sample options used to initialize new experimental USB
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# device stack. The scope of these options is limited to USB samples in project
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# tree, you cannot use them in your own application.
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source "samples/subsys/usb/common/Kconfig.sample_usbd"
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source "Kconfig.zephyr"

‎samples/subsys/usb/mtp/README.rst

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.. zephyr:code-sample:: usb-mtp
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:name: USB MTP
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:relevant-api: usbd_api _usb_device_core_api file_system_api
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Expose the selected storage partition(s) as USB Media device using Media Transfer Protocol driver.
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Overview
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********
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This sample app demonstrates the use of USB Media Transfer Protocol (MTP)
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driver provided by the Zephyr project. It allows the device to be mounted
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as a media device on the host system, enabling file transfers between the
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host and device.
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This sample can be found under :zephyr_file:`samples/subsys/usb/mtp` in the
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Zephyr project tree.
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Requirements
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************
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- USB device driver support.
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- Storage media with Littlefs/FAT filesystem support.
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- Partitions must be mounted before connecting the board to Host.
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Building and Running
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********************
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This sample can be built for multiple boards which can support at least one storage parition,
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in this example we will build it for the stm32f769i_disco board:
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.. zephyr-app-commands::
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:zephyr-app: samples/subsys/usb/mtp
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:board: stm32f769i_disco
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:goals: flash
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:compact:
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Running
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=======
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Plug the board into a host device, for example, a PC running Linux.
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The board will be detected as shown by the Linux dmesg command:
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.. code-block:: console
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usb 9-1: new full-speed USB device number 112 using uhci_hcd
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usb 9-1: New USB device found, idVendor=8086, idProduct=f8a1
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usb 9-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
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usb 9-1: Product: Zephyr MTP
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usb 9-1: Manufacturer: ZEPHYR
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usb 9-1: SerialNumber: 0123456789AB
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Once connected, the device should appear as a media device on your host system.
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You can then:
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- Browse the device storage
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- Transfer files to/from the device
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- Create/delete directories
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The storage contents will persist across device reboots as long as the
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filesystem is properly unmounted before disconnecting or resetting the device.
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.. note::
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Not All MTP Features are implemented, for example you can't move/copy
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files from within the device, it must be done via Host.
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Troubleshooting
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===============
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If the device is not recognized properly:
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1. Ensure the storage medium is properly initialized
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2. Check that the filesystem is mounted correctly
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3. Verify USB configuration is correct for your board
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4. Enable DEBUG logs on USB MTP driver to get more information
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For debugging purposes, you can enable USB debug logs by setting the following
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in your project's configuration:
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.. code-block:: none
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CONFIG_USBD_LOG_LEVEL_DBG=y
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CONFIG_USBD_MTP_LOG_LEVEL_DBG=y

‎samples/subsys/usb/mtp/boards/rpi_pico.overlay

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/*
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* Copyright (c) 2024 Kelly Lord
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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&flash0 {
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partitions {
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compatible = "fixed-partitions";
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#address-cells = <1>;
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#size-cells = <1>;
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storage_partition: partition@100000 {
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label = "storage";
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reg = <0x100000 DT_SIZE_M(1)>;
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};
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};
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};
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/ {
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fstab {
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compatible = "zephyr,fstab";
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lfs1: lfs1 {
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compatible = "zephyr,fstab,littlefs";
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read-size = <32>;
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prog-size = <32>;
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cache-size = <256>;
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lookahead-size = <64>;
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block-cycles = <512>;
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partition = <&storage_partition>;
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mount-point = "/lfs1";
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automount;
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mtp-enabled;
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};
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};
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};

‎samples/subsys/usb/mtp/boards/stm32f769i_disco.overlay

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/*
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* Copyright (c) 2025 Mohamed ElShahawi ([email protected])
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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/delete-node/ &storage_partition;
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&mx25l51245g {
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partitions {
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compatible = "fixed-partitions";
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#address-cells = <1>;
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#size-cells = <1>;
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storage_partition: partition@1a0000 {
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label = "storage";
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reg = <0x001a0000 DT_SIZE_M(40)>;
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};
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storage_partition2: partition@2ba0000 {
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label = "storage2";
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reg = <0x2ba0000 DT_SIZE_M(20)>;
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};
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};
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};
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/ {
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fstab {
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compatible = "zephyr,fstab";
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lfs1: lfs1 {
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compatible = "zephyr,fstab,littlefs";
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read-size = <32>;
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prog-size = <32>;
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cache-size = <256>;
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lookahead-size = <64>;
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block-cycles = <512>;
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partition = <&storage_partition>;
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mount-point = "/lfs1";
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automount;
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mtp-enabled;
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};
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lfs2: lfs2 {
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compatible = "zephyr,fstab,littlefs";
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read-size = <32>;
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prog-size = <32>;
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cache-size = <256>;
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lookahead-size = <64>;
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block-cycles = <512>;
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partition = <&storage_partition2>;
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mount-point = "/lfs2";
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automount;
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mtp-enabled;
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};
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};
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};

‎samples/subsys/usb/mtp/prj.conf

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CONFIG_USB_DEVICE_STACK_NEXT=y
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CONFIG_USBD_MTP_CLASS=y
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CONFIG_SAMPLE_USBD_PRODUCT="USBD MTP sample"
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CONFIG_SAMPLE_USBD_PID=0x0009
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CONFIG_LOG=y
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CONFIG_USBD_LOG_LEVEL_WRN=y
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CONFIG_UDC_DRIVER_LOG_LEVEL_WRN=y
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CONFIG_USBD_MTP_LOG_LEVEL_ERR=y
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CONFIG_USB_DEVICE_INITIALIZE_AT_BOOT=n
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CONFIG_FLASH=y
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CONFIG_FLASH_MAP=y
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CONFIG_FILE_SYSTEM=y
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CONFIG_FILE_SYSTEM_LITTLEFS=y
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CONFIG_USBD_THREAD_STACK_SIZE=3192

‎samples/subsys/usb/mtp/sample.yaml

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sample:
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name: USB MTP device class sample
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tests:
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sample.usb_device_next.mtp:
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depends_on: usbd
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tags: usb
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harness: console
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harness_config:
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type: one_line
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regex:
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- "USB device support enabled"

‎samples/subsys/usb/mtp/src/main.c

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/*
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* Copyright (c) 2019 Intel Corporation
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* Copyright (c) 2025 Mohamed ElShahawi ([email protected])
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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/**
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* @file
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* @brief Sample app for USB MTP class
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*
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* Sample app for USB MTP class driver. By default MTP class driver will expose
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* all storage partitions which has the flag `mtp-enabled`
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*/
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#include <sample_usbd.h>
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#include <zephyr/kernel.h>
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#include <zephyr/usb/usb_device.h>
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#include <zephyr/usb/usbd.h>
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#include <zephyr/logging/log.h>
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LOG_MODULE_REGISTER(usb_mtp_sample, LOG_LEVEL_INF);
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static void sample_msg_cb(struct usbd_context *const ctx, const struct usbd_msg *msg)
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{
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LOG_INF("USBD message: %s", usbd_msg_type_string(msg->type));
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if (usbd_can_detect_vbus(ctx)) {
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if (msg->type == USBD_MSG_VBUS_READY) {
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if (usbd_enable(ctx)) {
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LOG_ERR("Failed to enable device support");
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}
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}
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if (msg->type == USBD_MSG_VBUS_REMOVED) {
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if (usbd_disable(ctx)) {
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LOG_ERR("Failed to disable device support");
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}
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}
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}
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}
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int main(void)
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{
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struct usbd_context *sample_usbd;
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sample_usbd = sample_usbd_init_device(sample_msg_cb);
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if (sample_usbd == NULL) {
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LOG_ERR("Failed to initialize USB device");
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return -1;
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}
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if (usbd_enable(sample_usbd)) {
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LOG_ERR("Failed to enable device support");
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return -1;
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}
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LOG_INF("USB device support enabled\n");
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return 0;
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}

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