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      Introduction

      Introduction

        eCos support for USB Mass Storage Peripherals

        Currently, the eCos USB-Mass Storage Device (MSD) slave package

        provides support only for the SCSI transparent command set. The

        package flexibility allows future extension for other sub-class,

        .i.e. RBC, UFI etc..

        The package requires the actual storage media to use the eCos disk

        interface. Disk sector size is assumed 512 bytes.

        The USB-MSD package is not tied to any specific

        hardware. It requires the presence of USB hardware on the

        target and a suitable device driver to make endpoints

        available for this code to use. The configuration system

        cannot load the eCos package automatically for specific

        targets, in the way that a USB device driver or an ethernet

        driver can be loaded automatically. Instead, the package has

        to be added explicitly. When using the command line tools this

        will involve an operation like the following:

        $ ecosconfig add usbs_msd

        Typically, this will automatically cause the USB device driver

        to become active. The USB-Mass Storage Device driver runs as a

        thread, therefore requires the kernel package to be active. To

        start the MSD interface, user must call the usbs_msd_start()

        function. No other user intervention is required.

        The MSD driver will interact directly with the storage media.

        Care should be taken not to mount/use the filesystem present on

        the media while used as a mass storage. This could potentially

        damage the filesystem.

      Configuration

      Configuration

      Configuration USB Mass Storage Peripherals

        The USB Mass Storage Device interface uses the bulk transfer mode. It needs

        three endpoints for the communication with the host to be complete.

        The control endpoint (commonly EP0), the transmission and reception

        endpoints. The default CDL file contains configuration for

        the USB-Mass Storage Device 0. While it is uncommon to have several USB

        ports on a device, it is not impossible, hence user can update the package and

        create a second device .e.g. MSD1.

        Each endpoint shall be configured according to the underlying hardware.

        The endpoints configuration includes, the structure name, endpoint number

        and buffer size according to the USB chip specification.

        The control endpoint is selected with

        CYGDAT_IO_USB_SLAVE_MSD0_EP0.

        The default values is set to "usbs_at91_ep0". This is the control

        endpoint for the Atmel AT91 USB device driver.

         The TX and RX endpoints can be assigned statically or dynamically (assuming the USB

         device driver supports it). In case of static configuration, the bulk IN and bulk OUT

         endpoints are configured with CYGDAT_IO_USB_SLAVE_MSD0_TX_EP

         and CYGDAT_IO_USB_SLAVE_MSD0_RX_EP respectively.

        In addition, the  TX and RX enpoints number must be provided by the user.

        They are configured with  CYGNUM_IO_USB_SLAVE_MSD0_TX_EP_NUM

        and CYGNUM_IO_USB_SLAVE_MSD0_RX_EP_NUM

        In case of dynamic endpoints configuration, only the endpoint number is mandatory.

        The last endpoints configuration parameters are the entpoints buffer size. They are set with:

      CYGNUM_IO_USB_SLAVE_MSD0_EP0_MAX_PACKET_SIZE

      CYGNUM_IO_USB_SLAVE_MSD0_TX_EP_MAX_PACKET_SIZE

      CYGNUM_IO_USB_SLAVE_MSD0_RX_EP_MAX_PACKET_SIZE

        A mass storage device must stall one or both bulk endpoints in

        several situations. However, not all eCos USB device drivers seems

        to implement this functionality correctly. Hence, this option is

        disable by default. Testing shows that both Linux and Windows can

        handle mass storage device with stall disable as long as all data transfer phase

        are handled correctly. Enpoint stall can be enable with

        CYGSEM_IO_USB_SLAVE_MSD_STALL_ENABLE.

        The USB MSD device will make its vendor:product ID known to

        the host. This should be configured

        with CYGNUM_IO_USB_SLAVE_MSD0_VENDOR_ID and

        CYGNUM_IO_USB_SLAVE_MSD0_PRODUCT_ID NOTE:

        The default configurations are not valid for commercial products, but

        should work for testing.

        The USB enumeration also contains text strings to describe the

        device. The manufacturer string can be set with

        CYGDAT_IO_USB_SLAVE_MSD0_MFG_STR. The product name

        can be set with CYGDAT_IO_USB_SLAVE_MSD0_MFG_STR,

        finally, the serial number can be set

        with CYGDAT_IO_USB_SLAVE_MSD0_SERIAL_STR.

        To access the storage media, the USB MSD package requires the storage

        media to use the eCos disk interface. The disk sector size is assumed

        to be 512 bytes. Multiple logical units are supported by the package

        (2 by default).

        More logical units can be supported by changing the

        USBS_MSD_CBW_MAX_LUN definition according

        to the user needs. Two logical units can be either 2 partitions on the same

        disk or 2 partitions on 2 different physical disks.

        The first logical unit can be set with

        CYGDAT_IO_USB_SLAVE_MSD0_LUN0_NAME. The default value

        is assigned to "/dev/ramdisk0/1", the first partition of the ramdisk

         used by the test application.

      Host Configuration

      Host Configuration

      Host Configuration for USB Mass Storage like Peripherals

        With modern host operating system, no specific configuration of the

        host shall be required to bring up the eCos USB-Mass Storage Device.

       The USB-Mass Storage device will respond to a set of SCSI commands:

      INQUIRY

      READ_CAPACITY

      READ_10

      WRITE_10

      REQUEST_SENSE

      TEST_UNIT_READY

      and partially to the commands:

      SENSE_6

      VERIFY_10

      REVENT_ALLOW_MEDIUM_REMOVAL

      Example

      Example

      Example for USB Mass Storage like Peripherals

        The "ram disk" is a test application supplied to verify / debug the USB-Mass Storage

        package. The minimal functionality of this test case is to create a tiny "ram disk"

        device large of around 32 sectors of 512 bytes each. The disk devtab entry

        is "/dev/ramdisk0". A FAT12 filesystem is created on top of it

        as the first partition of the disk. The partition is therefore accessible from

        "/dev/ramdisk0/1". The default behavior of the application is to

        start the USB MSD thread. Once plugged into the host machine, an empty drive

        called eCos-3.0 shall appear in the host explorer.

        To test further, the FAT filesystem package can be included while compiling the test

        application. If included, before the MSD driver is started, the application will

        create 2 files (fee and foo) and 1 directory (bar) in the filesystem. Both files and

        directory shall appear in the host explorer.

        The test application was primarly tested with the AT91 architecture. The control

        endpoint is set to "usbs_at91_ep0" and the buffer size

        to 8 bytes.

        The TX endpoint is set to "usbs_at91_ep1" and the buffer size

        to 64 bytes (with Tx (USB IN) endpoint number set to 1).

        The RX endpoint is set to "usbs_at91_ep2" and the buffer size

        to 64 bytes (with Rx (USB OUT) endpoint number set to 2).