USB Component  Version 6.17.0
MDK Middleware for USB Device and Host Communication
MSC: Mass Storage Class

USB Host functions to support Mass Storage Class (MSC) USB Devices. More...


 User API
 User API reference of the Mass Storage Class.
 Configuration of the USB Host MSC Class in ┬ÁVision.


USB Host functions to support Mass Storage Class (MSC) USB Devices.

The Mass Storage Class (MSC) in the USB Host Component provides physical access to a data storage device. The USB MSC drive in the File System Component gives file I/O access to that data storage.

Software Stack
The following picture shows how the software stack is built-up for MSC device support:

Refer to:

Software Structure
The application starts the USB Host by calling USBH_Initialize. The USB Host Core will wait until an USB MSC device is attached to the system. As soon as this happens it will enumerate the device and it will be ready to be used by the application.

The data functions USBH_MSC_Read and USBH_MSC_Write can be either called by the user thread directly or called indirectly when the user thread is using file system routines like fread/fwrite which use the USB MSC Device as media for data storage.



Steps to create an USB Host application with MSC support:

User Code Template USBH_MSC.c

* MDK Middleware - Component ::USB:Host:MSC
* Copyright (c) 2004-2020 Arm Limited (or its affiliates). All rights reserved.
* Name: USBH_MSC.c
* Purpose: Functions to access USB storage device via USB Host
* Rev.: V6.4.3
* USBH_MSC.c is a code template for the application specific functionality of
* the USB Host MSC class. It implements the access to a USB storage device and
* allows file I/O via the File System component.
* USBH_MSC.h is the related header file.
* First to enable USB Host Controller (if not already enabled) call:
* USBH_Initialize (ctrl_num);
* To access files on a USB storage device use below code sample:
* int32_t media_status, media_status_previous = USBH_MSC_ERROR_DRIVE;
* for (;;) {
* media_status = USBH_MSC_DriveGetMediaStatus (drive_name);
* if ((media_status == USBH_MSC_OK) &&
* (media_status_previous != USBH_MSC_OK)) {
* switch (USBH_MSC_DriveMount (drive_name)) {
* case USBH_MSC_OK:
* fopen (...);
* break;
* fformat (drive_name, "/FAT32");
* fopen (...);
* break;
* // Mount error
* break;
* }
* }
* media_status_previous = media_status;
* osWait (1000); // polling interval for media status (1 second)
* }
* Now file I/O can be performed using fopen, fread, fwrite, fclose and other
* functions of the File System component
* When drive is not to be used any more call:
* USBH_MSC_DriveUnmount (drive_name);
* When USB Host Controller is not to be used any more call:
* USBH_Uninitialize (ctrl_num);
#include <stdint.h>
#include "RTE_Components.h" // Component selection
#include "USBH_MSC.h" // Access storage via USB Host
#if (!defined (RTE_FileSystem_Drive_USB_0) && !defined (RTE_FileSystem_Drive_USB_1))
#error "Project does not contain USB storage device support"
int32_t USBH_MSC_DriveGetMediaStatus (const char *drive_name) {
usbStatus ustatus;
uint8_t drive_num;
drive_num = (uint8_t)(drive_name[1] - '0'); // get drive number from drive name
ustatus = USBH_MSC_GetStatus (drive_num);
if (ustatus != usbOK) return USBH_MSC_ERROR_DRIVE;
return USBH_MSC_OK;
int32_t USBH_MSC_DriveMount (const char *drive_name) {
fsStatus fstatus;
fstatus = finit (drive_name);
if (fstatus != fsOK) return USBH_MSC_ERROR;
fstatus = fmount (drive_name);
switch (fstatus) {
case fsOK:
case fsNoFileSystem:
case fsError:
case fsUnsupported:
case fsAccessDenied:
case fsInvalidParameter:
case fsInvalidDrive:
case fsInvalidPath:
case fsUninitializedDrive:
case fsDriverError:
case fsMediaError:
case fsNoMedia:
case fsNoFreeSpace:
case fsFileNotFound:
case fsDirNotEmpty:
case fsTooManyOpenFiles:
case fsAlreadyExists:
case fsNotDirectory:
return USBH_MSC_OK;
int32_t USBH_MSC_DriveUnmount (const char *drive_name) {
fsStatus fstatus;
fstatus = funmount (drive_name);
if (fstatus != fsOK) return USBH_MSC_ERROR;
fstatus = funinit (drive_name);
if (fstatus != fsOK) return USBH_MSC_ERROR;
return USBH_MSC_OK;
uint64_t USBH_MSC_DriveGetCapacity (const char *drive_name) {
usbStatus ustatus;
uint32_t block_count;
uint32_t block_size;
uint8_t drive_num;
drive_num = (uint8_t)(drive_name[1] - '0'); // get drive number from drive name
ustatus = USBH_MSC_GetStatus (drive_num);
if (ustatus != usbOK) return 0;
ustatus = USBH_MSC_ReadCapacity (drive_num, &block_count, &block_size);
if (ustatus != usbOK) return 0;
return (((uint64_t)block_count) * ((uint64_t)block_size));