MSC: Mass Storage Class

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

Content
	User API
	User API reference of the Mass Storage Class.
	Configuration
	Configuration of the USB Host MSC Class in µVision.

Description

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:

• MSC: Mass Storage Class for an overview of the MSC class.
• USB Host Mass Storage for an example project that uses the MSC class.

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.

Implementation

Steps to create an USB Host application with MSC support:

• In the Manage Run-Time Environment window select USB:Host:MSC for support of the MSC class and File System:CORE, File System:Drive:USB for using the File System Component with support for USB mass storage devices. For the File System:Drive:USB you have to set the number to the number of devices you need to support simultaneously.
• Configure the number of USB MSC devices connected in the file USBH_Config_MSC.h.
• Use the functions of the related file (USBH_MSC.c) to access the data storage.

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;
 *         case USBH_MSC_ERROR_FORMAT:
 *           fformat (drive_name, "/FAT32");
 *           fopen (...);
 *           break;
 *         case USBH_MSC_ERROR:
 *           // 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"
#endif
 
 
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:
      break;
    case fsNoFileSystem:
      return USBH_MSC_ERROR_FORMAT;
    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_ERROR;
  }
 
  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));
}