U.S. patent application number 14/475595 was filed with the patent office on 2015-01-01 for interface for extending functionality of memory cards.
The applicant listed for this patent is Google Inc.. Invention is credited to Yaron Segalov, Itay Sherman.
Application Number | 20150006797 14/475595 |
Document ID | / |
Family ID | 39686838 |
Filed Date | 2015-01-01 |
United States Patent
Application |
20150006797 |
Kind Code |
A1 |
Sherman; Itay ; et
al. |
January 1, 2015 |
INTERFACE FOR EXTENDING FUNCTIONALITY OF MEMORY CARDS
Abstract
An enhanced flash memory card, including a memory including a
file management system for storing files within directories, the
files and directories being identified by respective file names and
directory names, and a controller that interfaces with a host
device and that reports to the host device names of files and
directories stored in the memory, although no files and directories
having the reported names actually exist in the memory.
Inventors: |
Sherman; Itay; (Hod
Hasharon, IL) ; Segalov; Yaron; (Tel Aviv,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Google Inc. |
Mountain View |
CA |
US |
|
|
Family ID: |
39686838 |
Appl. No.: |
14/475595 |
Filed: |
September 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13164773 |
Jun 21, 2011 |
8832161 |
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14475595 |
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11725691 |
Mar 20, 2007 |
7966355 |
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13164773 |
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60901368 |
Feb 13, 2007 |
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Current U.S.
Class: |
711/103 |
Current CPC
Class: |
G06F 3/0643 20130101;
G06F 3/0646 20130101; G06F 2003/0692 20130101; G06F 3/0679
20130101; G06F 3/0664 20130101; Y02D 30/70 20200801; G06F 3/0623
20130101; G06F 16/166 20190101; G06F 3/0667 20130101; G06F 3/0605
20130101; G06F 16/1847 20190101; G06F 3/0659 20130101; Y02D 70/122
20180101 |
Class at
Publication: |
711/103 |
International
Class: |
G06F 3/06 20060101
G06F003/06; G06F 17/30 20060101 G06F017/30 |
Claims
1-22. (canceled)
23. An enhanced flash memory card, comprising: a memory comprising
a file management system for storing files within directories, the
files and directories being identified by respective file names and
directory names; and a controller that interfaces with a host
device and that reports to the host device a name of a directory
stored in said memory, the reported directory name corresponding to
a service provided by the enhanced flash memory card to the host
device, although no directory having that reported name actually
exists in said memory.
24. The enhanced flash memory card of claim 23, wherein said
controller reports to the host device a file name stored in said
memory, the reported file name corresponding to a control for an
application that executes on the enhanced flash memory card,
although no file having that reported name actually exists in said
memory.
25. The enhanced flash memory card of claim 24, wherein said
controller is operative to activate a control, in response to
receiving a command from the host device to open a specific file,
although no file having the name of the specific file actually
exists in said memory.
26. The enhanced flash memory card of claim 23 further comprising a
radio, wherein said controller reports to the host device a
directory named "Radio", although no directory having such name
actually exists in said memory, and wherein said controller is
operative to activate said radio, in response to receiving a
command from the host device to select the "Radio" directory.
27. The enhanced flash memory card of claim 26, wherein said
controller reports to the host device that the directory named
"Radio" contains a file named "Search Forward", although no file
having such name actually exists in said memory, and wherein said
controller is operative to instruct said radio to skip to a next
radio channel, in response to receiving a command from the host
device to open the "Search Forward" file.
28. The enhanced flash memory card of claim 26, wherein said
controller reports to the host device that the directory named
"Radio" contains a file named "Volume Up", although no file having
such name actually exists in said memory, and wherein said
controller is operative to instruct said radio to increase its
volume, in response to receiving a command from the host device to
open the "Volume Up" file.
29. The enhanced flash memory card of claim 23, further comprising
a communication modem, and wherein a directory name reported by
said controller to the host device corresponds to a name of a
remote server accessible by said communication modem, although no
directory having that reported name actually exists in said
memory.
30. The enhanced flash memory card of claim 29, wherein a file name
reported by said controller to the host device corresponds to a
file or a stream that is stored on the remote server, although no
file having that reported name actually exists in said memory.
31. The enhanced flash memory card of claim 30, wherein said
controller is operative to access a file or stream stored on a
remote server and download it to said memory, in response to
receiving a command from the host device to open a specific file,
although no file having the name of the specific file actually
exists in said memory.
32. The enhanced flash memory card of claim 30, wherein said
controller is operative to upload a file to a remote server, in
response to receiving a command from the host device to write to a
designated location in said memory.
33. The enhanced flash memory card of claim 23, wherein said
controller reports to the host device a directory named "ATComm",
although no directory having such name actually exists in said
memory, and wherein said controller is operative to issue an AT
command to said communication modem, in response to receiving a
command from the host device to write the text of the AT command to
a file in the "ATComm" directory.
Description
PRIORITY REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional
Application No. 60/901,353, entitled INTERFACE FOR EXTENDING
FUNCTIONALITY OF MEMORY CARDS, filed on Feb. 13, 2007 by inventor
Itay Sherman.
FIELD OF THE INVENTION
[0002] The present invention relates to flash memory cards.
BACKGROUND OF THE INVENTION
[0003] Most CE and mobile computing devices today support addition
of flash memory storage cards in the forms of SD, MiniSD, MicroSD
and MMC, to expand memory capabilities of the devices. Access to
such expansion memory cards is generally based on a file system and
a standard access protocol that conforms to the SD or MMC
specifications.
SUMMARY OF THE DESCRIPTION
[0004] The present invention is used to extend the functionality of
SD cards, beyond the local storage functionality that is currently
provided. Using the present invention, SD cards can provide wired
or wireless communication channels to access remote content
servers, and can stream content from, upload content to and
download content from these servers.
[0005] Using the present invention, SD cards can also include
applications that are controlled and displayed by the host device,
and implemented on the CD card.
[0006] The SD cards of the present invention are compatible with
existing SD physical and logical interfaces, and operate
transparently with host devices that include SD slots.
[0007] There is thus provided in accordance with an embodiment of
the present invention an enhanced flash memory card, including a
flash memory card, including a wireless modem for downloading
remote directory listings, and media files and streams over the
Internet, and a memory partitioned into physical data storage
clusters, and a driver for the flash memory card (i) for managing a
file allocation table (FAT) that stores information about physical
and virtual data storage clusters, the FAT including stub files for
remote directory listings and remote media files and streams,
wherein the stub files link to virtual data clusters, (ii) for
managing a download conversion map from virtual cluster numbers to
pointers of remote media files and streams, and (iii) for storing
downloaded directory listings and media files and streams in the
physical data storage clusters.
[0008] There is additionally provided in accordance with an
embodiment of the present invention a method for remote file access
using flash memory, including issuing a read request from a host
device to a flash memory file system, the flash memory being
represented as a plurality of physical and virtual data storage
clusters, wherein the read request is addressed to a virtual data
cluster, reading a stub file from a physical data cluster of the
flash memory that corresponds to the virtual data cluster,
identifying a URL that corresponds to the virtual data cluster,
receiving remote file data from the URL, and storing the remote
file data in physical data clusters of the flash memory.
[0009] There is further provided in accordance with an embodiment
of the present invention a method for file upload using flash
memory, including issuing a write request from a host device to a
flash memory file system, the flash memory being represented as a
plurality of physical and virtual data storage clusters, wherein
the write request is to a directory represented as a stub file in
the virtual storage, re-directing the write request to a physical
cluster that holds an outgoing directory, writing the file content
to a file created in the outgoing directory, sending the created
file from the outgoing directory to a designated remote server, and
removing the file from the physical storage and from being listed
in the outgoing directory listing, after completion of the
sending.
[0010] There is yet further provided in accordance with an
embodiment of the present invention a method for file management,
including implementing a file system that includes (i) visible
physical sectors, (ii) hidden physical sectors, and (iii) virtual
sectors, wherein visible physical sectors are mapped to the file
system, hidden physical sectors are not mapped to the file system,
and virtual sectors are not resident in a physical memory, mapping
a virtual sector to a hidden sector in response to a read or a
write command to the virtual sector, prior to performing the read
or write command, and performing at least one auxiliary action in
response to the read or a write command to the virtual sector.
[0011] There is moreover provided in accordance with an embodiment
of the present invention an enhanced flash memory card, including a
flash memory card, including a memory, and a wireless modem for
downloading remote directory listings, and media files and steams
over the Internet, and a driver for the flash memory card for
managing a system of files and directories in the memory, and for
invoking an auxiliary action directed to the wireless modem,
wherein the auxiliary action is associated with a designated
directory.
[0012] There is additionally provided in accordance with an
embodiment of the present invention an enhanced flash memory card,
including a flash memory card, including a memory, and a media
player, and a driver for the flash memory card for managing a
system of files and directories in the memory, and for invoking an
auxiliary action directed to said media player, wherein the
auxiliary action is associated with a designated directory.
[0013] There is further provided in accordance with an embodiment
of the present invention a method for embedding a wireless modem in
a flash memory card, including managing a system of files and
directories in a flash card memory storage; generating an AT modem
command in response to receiving a write command to a file within a
designated directory, comprising copying text specified in the file
write command for inclusion in the associated AT command, and
issuing the AT modem command for a wireless modem embedded within
the flash card.
[0014] There is yet further provided in accordance with an
embodiment of the present invention a method for embedding a media
player in a flash memory card, including managing a system of files
and directories in a flash card memory storage, generating a media
player command in response to receiving a command to open a file
within a designated directory, wherein the media player command
corresponds to the name of the file, and issuing the media player
modem command to a media player embedded within the flash card.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention will be more fully understood and
appreciated from the following detailed description, taken in
conjunction with the drawings in which:
[0016] FIG. 1 is a simplified diagram of a prior art SD card
interface;
[0017] FIG. 2 is a simplified diagram of an SD card interface that
provides extended functionality, in accordance with the present
invention;
[0018] FIG. 3 is a simplified illustration of an arrangement of
clusters in an SD card file system, in accordance with an
embodiment of the present invention;
[0019] FIG. 4 is a simplified flowchart of a method for downloading
a file from a remote server to an SD card, in accordance with an
embodiment of the present invention;
[0020] FIG. 5A is a snapshot of a user interface and a file system
for a simplified example use case of file downloading, at a stage
where a user is browsing a remote directory, in accordance with an
embodiment of the present invention;
[0021] FIG. 5B is a snapshot of a user interface and a file system
for a simplified example use case of file downloading, at a stage
where a user is issuing a request to download a file from a remote
server, in accordance with an embodiment of the present
invention;
[0022] FIG. 5C is a snapshot of a user interface and a file system
for a simplified example use case of file downloading, at a stage
where a file from a remote server is being downloaded, in
accordance with an embodiment of the present invention;
[0023] FIG. 5D is a snapshot of a user interface and a file system
for a simplified example use case of file downloading, at a stage
where download of a file from a remote server is complete, in
accordance with an embodiment of the present invention;
[0024] FIG. 6 is a simplified flowchart of a method for generating
a stub file, in accordance with an embodiment of the present
invention;
[0025] FIG. 7 is a simplified flowchart of a method for playing a
streamed file from an SD card, in accordance with an embodiment of
the present invention;
[0026] FIG. 8 is an illustration of file streaming using a circular
cluster cycle in the FAT, in accordance with an embodiment of the
present invention;
[0027] FIG. 9 is a simplified flowchart of a method for uploading a
file from an SD card to a remote server, in accordance with an
embodiment of the present invention;
[0028] FIG. 10A is a snapshot of a user interface and a file system
for a simplified example use case of file uploading, at a stage
where a user is selecting a file to upload to a remote server, in
accordance with an embodiment of the present invention; and
[0029] FIG. 10B is a snapshot of a user interface and a file system
for a simplified example use case of file uploading, at a stage
where a file is being uploaded to a remote server, in accordance
with an embodiment of the present invention.
DETAILED DESCRIPTION
[0030] The present invention concerns an improved SD memory card
that provides extended functionality, including (i) wired or
wireless communication channels for accessing remote content
servers, and (ii) applications that are controlled and displayed by
an SD host device, but are implemented on the SD card. Using the
improved SD memory card of the present invention, a device such as
an MP3 or MP4 player, can stream music or video from remote content
servers, download files from these servers, and upload files to
these servers.
[0031] Reference is now made to FIG. 1, which is a simplified
diagram of a prior art SD card interface. Shown in FIG. 1 is a host
device 100 having an SD slot, and a conventional SD card 110 that
can be inserted in the SD slot. A channel 120 enables data
communication between host device 100 and SD card 110. Channel 120
also enables SD card 110 to receive electrical power from host
device 100.
[0032] Host device 100 includes a CPU 130 that is
software-controlled to process an SD instruction stack. Host device
100 also includes an SD driver 140.
[0033] SD card 120 includes an SD slave controller 150, for
accessing a file system that is stored on flash memory 160.
[0034] Reference is now made to FIG. 2, which is a simplified
diagram of an SD card interface that provides extended
functionality, in accordance with the present invention. Shown in
FIG. 2 is the same host device 100 as in FIG. 1, and an enhanced SD
card 210. Enhanced SD card 210 uses the same interface as standard
SD card 110, and thus operates seamlessly with host device 100.
Host device also includes an application 290 that performs the
extended functionality enabled by enhanced SD card 210. Details of
operation of application 290 are described hereinbelow with
reference to FIG. 4.
[0035] Enhanced SD card 210 includes an SD slave controller 250 and
flash memory 260. Slave controller 250 interfaces with host device
100 as a standard SD card, and provides information for a virtual
file system. Improved SD card 210 includes a CPU 270 controlled by
embedded software, and a communication modem 280 that interfaces
with other devices and networks. Communication modem 280 may be
inter alia a cellular modem, a WLAN modem, a WPAN modem, and a
wireless modem.
[0036] The file and directory structure reported by slave
controller 250 to host device 100 does not necessarily reflect
files and directories that are stored an SD card 210. Directory
names may represent names of remote servers accessible via
communication modem 280, and they may represent names of services
the SD card 210 provides. The operation of opening a directory by
the host, signals CPU 270 to access a specific server or activate a
specific service.
[0037] In accordance with the present invention, file names may
represent names of files or streams that are stored remotely on a
selected server. Opening a specific files triggers SD card 210 to
access the remote file or stream and download it to the card.
Immediate access to the file by the host is provided via a dummy
copy of the file that may include a place holder message such as
"file is currently being downloaded, download will be complete
within xx seconds". The place holder message may be provided in the
form of an audio file, such as an MP3 or WMA file, or an image
file, such as a JPEG of GIF file, depending on the type of file
that was requested.
[0038] Writing a file to a designated location on SD card 210
operates to upload the file to the selected remote server.
[0039] In accordance with the present invention, file names may
also be used to designate controls for applications that are
executed on SD card 210. Opening of a file designates activation of
a corresponding control.
[0040] For one usage scenario, SD card 210 may have a directory
named "Radio". Selection of this directory activates a radio on the
card. In turn, the Radio directory includes a list of files with
names "Search Forward", "Search Backward", "Volume Up" and "Volume
Down". Opening the "Search Forward" file, for example, activates an
instruction to the radio to skip to the next channel.
[0041] For another usage scenario, host device 100 writes to a file
in a directory named "ATComm". In response, an AT command, which
includes content written to the file, is issued to communication
modem 280. Thus, if the host writes "ATZ" to the file, which is a
reset command, the command is transmitted to communication modem
280. The modem reply, which is typically "OK", is written to a
second file in the ATComm directory, available for host device 100
to read.
[0042] For devices that support more advanced data formats such as
HTML pages or Java applications, SD card 210 provides a graphical
user interface via an HTML file or Java application file that is
stored on the card. The host device opens and executes such file,
e.g., main.html, which in turn provides a graphical representation
for accessing remote files or for controlling an application on SD
card 210. File content and HTML links are changed dynamically
corresponding to changes in information or changes in status.
[0043] With the graphical user interface, control over SD card 210
is still performed by selecting, opening and writing to files, but
the interface is graphical, as coded in the HTML file or Java
application.
Implementation Details
[0044] As described hereinabove, directory names on SD card 210 may
represent names of remote servers, and file names on SD card 210
may correspond to names of remote files and streams. Reference is
now made to FIG. 3, which is a simplified illustration of an
arrangement of clusters in an SD card file system, in accordance
with an embodiment of the present invention. Shown in FIG. 3 is a
flash memory in SSD card is represented as including 60 clusters,
numbered consecutively from 1 to 60, although clusters 31-60 are
virtual, non-physical clusters, as described in detail in what
follows.
[0045] The physical memory on SD card 210 is generally partitioned
into 512 byte sectors, and four sectors are combined to form a 2 KB
cluster, although it will be appreciated by those skilled in the
art that other partitions are within the scope of the present
invention. In FIG. 3 the physical memory includes clusters 1-30.
Information regarding available clusters on the SD card 210 is
maintained in a file allocation table (FAT). For each cluster, two
bytes are stored in the FAT, as follows.
0, if cluster is empty Next cluster in file, if cluster is not the
last cluster in a file 0xFFF8, if cluster is the last cluster in a
file 0xFFF7, if cluster is a bad cluster
[0046] Clusters 1-6 of FIG. 3 correspond to an MP3 file that is
stored as a cluster chain. The first cluster in the chain is
cluster 1, and the chain continues through clusters 2, 3, 4, 5 and
6, with cluster 6 being the last cluster in the file, designated as
an EOF (end-of-file) cluster. The arrows drawn in these clusters
represent pointers that advance through the chain of clusters.
Clusters 7-9 of FIG. 3 correspond to an MP3 file that is currently
being downloaded. As such, cluster 9 is not necessarily an EOF
cluster since additional downloaded data may require additional
clusters for storage. Similarly, clusters 26-28 correspond to a
second MP3 file that is currently being downloaded. Clusters 23 and
24 correspond to an MP4 file that is currently being downloaded.
Clusters 10-22 and 25, 29 and 30 are free clusters. The
cross-hatching in the clusters of FIG. 3 corresponds to the type of
cluster, as indicated in the FAT legend.
[0047] Information about files is stored in a directory, designated
"ROOT DIRECTORY" in FIG. 3, having 32 byte directory entries
generally including the following information.
File name with 8+3 characters Type--regular file, directory File
size Date & time First cluster of file File names longer than
8+3 characters are obtained by including additional entries for the
same file with special attributes. The directory itself is stored
in the file system as a regular file.
[0048] In the implementation of the present invention illustrated
in FIG. 3, the SD file system is extended by declaring the volume
to be of a size larger than the amount of available physical flash
memory. Host device 100 is not aware of the discrepancy since it
never needs to write to the excess volume.
[0049] The extended volume includes physical clusters, which are
mapped to real flash memory locations, and virtual clusters, which
have addresses beyond the available flash memory. Cluster 1-30 in
FIG. 3 are physical clusters, and clusters 31-60 are virtual
clusters. Upon initialization, the virtual clusters may be marked
as bad clusters in the FAT, thereby ensuing that host device 100
does not try to write to these clusters. More generally, when host
device is powered up, the flash memory is reset by erasing all file
entries in the root directory and clearing the FAT. Physical
clusters are marked as being free clusters, and virtual clusters
may be marked as being bad clusters.
[0050] Virtual clusters are converted to stub locations when they
are read. Stub locations include a directory list stub and a media
stub, such as an MP3 stub. A directory list stub includes a file
with a place holder message such as "file is currently being
downloaded, download will be complete within xx seconds", as
described hereinabove. A virtual cluster is mapped to an
appropriate stub location in the flash memory in such a way that
distinct virtual clusters correspond to distinct stub files.
[0051] Clusters 31 and 37 in FIG. 3 are directory list stubs.
Clusters 44-46, clusters 50-52 and clusters 59-60 are media stubs.
Media stubs are cluster chains that end at an EOF cluster. Clusters
44-46 and clusters 50-52 correspond to an MP3 stub, and cluster
59-60 corresponds to an MP4 stub. Clusters 32-36, 38-43, 47-49 and
53-58 are marked as bad clusters. It is noted that MP3 stubs are
generally identical, since they generally contain the same place
holder message. More generally, media stubs for a specific media
type, such as MP3 stubs, JPG stubs or MP4 stubs, are identical.
[0052] The number of virtual clusters that are defined equals N*M,
where N is the maximum number of concurrent stubs required, and M
is the maximum number of clusters for stub data. Typically, one
cluster is used for a directory list stub, and 50 clusters,
corresponding to 100 KB, are used for a media stub. For simplicity,
FIG. 3 is drawn with N=5 and M=6. In practice, reasonable values
for N and M are 256 and 64, respectfully, and accordingly the
number of virtual clusters is 2 14. As such, the virtual clusters
require 32 KB for their FAT entries.
[0053] A portion of the flash memory, designated in FIG. 3 as "STUB
STORAGE AREA", that contains M clusters is used to stub file data
and is not mapped to the file system. Only SD controller 250 can
access this storage area of the flash memory. The M clusters in the
stub storage area are hidden clusters; specifically, they are
physical clusters in the flash memory but they are not mapped
directly on the FAT. When virtual clusters are read, the virtual
cluster locations are converted to hidden cluster locations.
[0054] Stub files have valid directory entries, which point to
virtual clusters as the first file cluster. All subsequent clusters
in the stub files are also virtual clusters. Referring to FIG. 3,
clusters 44-46, clusters 50-52 and clusters 59-60 are cluster
chains for stub files. Each stub file points to a different virtual
cluster, although they may contain the same stub data.
Consequently, SD controller 250 knows which file to download based
upon the virtual sector number requested by host device 100.
Specifically, the hidden sector number to read from the stub
storage area is V (mod 4M), where V is the virtual sector offset
inside the virtual sector area. The term 4M arises from the 4
sectors per cluster. More generally, if there are K sectors per
cluster, then the hidden sector number to read is V (mod K*M).
[0055] When a remote file or stream is downloaded, it is stored on
SD card 210 in a FAT cluster chain, just as a local file is stored.
However, the directory entry for the file does not point to the
first cluster in the chain. A download map from virtual cluster
number to {file name, file type, pointer to file on remote server,
first real cluster} is used to maintain a list of all current stub
files, including files in stub mode and files in downloading mode.
Links that can be clicked on by a user have entries in the download
map, along with a stub file directory entry with a file type of the
form DIRECTORY, MP3, MP3_STREAM, or such other media type. When a
file is finished being downloaded, it is removed from the download
map.
[0056] Shown in FIG. 3 is a download map with entries for two
directories and two MP3 files, corresponding to the stubs in the
root directory. The MP3 files being downloaded are currently stored
in clusters 7-9 and clusters 23 and 24.
[0057] Reference is now made to FIG. 4, which is a simplified
flowchart of a method for downloading a file from a remote server
to an SD card, in accordance with an embodiment of the present
invention. To accompany FIG. 4, reference is also made to FIGS.
5A-5D, which are snapshots of a user interface and a file system
for a simple example use case, during various stages of file
download during operation of the method of FIG. 4. Each of FIGS.
5A-5D are divided into three portions. The leftmost portion
illustrates a user interface, the middle portion illustrates
directory entries and the download map, and the rightmost portion
illustrates the FAT. Thus, whereas FIG. 4 describes the steps being
performed, the accompanying FIGS. 5A-5D illustrate states of the
user interface and the file system during various ones of the
steps. The legends for the cross-hatching on the FATs in FIGS.
5A-5D are the same as the legend provided in FIG. 3. It will be
appreciated by those skilled in the art that the file system
illustrated in FIGS. 5A-SD is simplified, in order to emphasize the
workings of an embodiment of the present invention.
[0058] Referring to FIG. 4, in general at step 405, application 290
analyzes a downloaded directory file for new stub files to create.
The directory content is recursively searched by application 290.
For each file discovered a directory listing stub or media stub is
created, corresponding to the file type.
[0059] FIG. 5A corresponds to an initial stage wherein a user is
browsing a downloaded remote directory listing, as shown in the
leftmost portion of FIG. 5A. At this stage, the root directory has
entries for two stub directories; namely, a "jazz" stub directory
at virtual cluster 31, and a "rock" stub directory at virtual
cluster 37. The root directory also has entries for two local
files; namely, a movie stored at clusters 1-6, and a pop song
stored at clusters 7-9. The download map has URL entries for two
remote directories; namely, a "jazz" directory at virtual cluster
31 has URL http://music.com/jazz, and a "rock" directory at virtual
cluster 37 has URL http://music.com/rock.
[0060] Reference is now made to FIG. 6, which is a simplified
flowchart of a method for generating a stub file in step 405 of
FIG. 4, in accordance with the present invention. At step 610,
application 290 searches the virtual clusters in the FAT, such as
clusters 31-60 in FIG. 5A, for the first free row; namely, the
first row with dusters marked as bad clusters. At step 620 the
first applicable cluster in the row found at step 610 is set as the
first cluster of the stub file, according to the type of stub file.
Specifically, for the example FAT shown in FIG. 3, the applicable
cluster for directory list stubs is the first cluster in the row,
for MP3 stubs is the second cluster in the row; and for MP4 stubs
is the fifth cluster in the row. Such an arrangement ensures that
the different types of stubs correspond to different hidden cluster
in the sub storage area.
[0061] At step 630, application 290 allocates additional virtual
clusters, as required for storing the stub file, and the additional
virtual clusters are chained to the first virtual cluster. Such
virtual cluster chains are shown in FIG. 5B as clusters 44-46 and
clusters 50-52. Finally, at step 640, application 290 modifies the
directory entry for the stub file, so that the first cluster of the
stub file points to the first cluster from step 620, and so that
the size of the stub file matches the actual length of the stub
file.
[0062] At step 410, host device 100 refreshes and identifies the
newly-downloaded directory listing. At step 415 a determination is
made whether a file is to be downloaded. If so, processing advances
to step 425. Otherwise, processing ends.
[0063] As shown in FIG. 5A, the user clicks on the "jazz"
directory. Momentarily, a place holder message "downloading file
list please wait" appears on the user interface. The place holder
message is stored in the stub storage area, as shown in FIG. 3, in
the hidden cluster corresponding to cluster 31. In the meantime,
host device 100 downloads the remote file list for the "jazz"
directory, and displays the list shown at the top of the leftmost
portion of FIG. 5B. The list contains two files; namely, a "benny
goodman" MP3 file, and a "louis armstrong" MP3 file.
[0064] At this stage, the root directory includes a local directory
for the "jazz" directory at data cluster 13. A "jazz" directory is
generated, and includes entries for two stub MP3 files; namely, a
stub MP3 file at virtual cluster 44, and a stub MP3 file at virtual
cluster 50. The download map includes URLs for the remote "benny
goodman" and "louis armstrong" files. The user clicks on "benny
goodman" to initiate download of that file.
[0065] Referring back to FIG. 4, in general at step 420 host device
100 issues a file read request to the SD file system. The request
is transmitted to SD driver 140. SD driver determines from the FAT,
which appropriate cluster to read, and finds the cluster value,
which corresponds to a virtual cluster. Host device 100 is unaware
that the cluster value corresponds to a non-physical cluster, and
interprets the value as a legitimate cluster value.
[0066] At step 425, SD driver 140 transmits the read request to SD
controller 250. SD driver converts the virtual cluster value to a
virtual sector value, using a conversion of the form K*V+constant,
and issues a read request to the virtual sector. As above, the
parameter K is the number of sectors per cluster.
[0067] At step 430, SD controller 250 receives the read request. In
response, SD controller 250 sends a command to SD application 290
including the virtual sector value, and returns the corresponding
hidden sector value to host device 100, using the formula hidden
sector=virtual_sector (mod(K*M).
[0068] At step 435, application 290 receives the event from SD
controller 250, and converts the sector value to a URL, or to
another such pointer to a file on a remote server, using the
download map. Application 290 then issues an HTTP GET command, or
such other download command, to retrieve the remote file. This
operation is performed only once, when the first sector of the file
is read.
[0069] At step 440, SD driver 140 retrieves the stub data. Host
device 100 is unaware that this data belongs to a stub file. The
length matches the file length in the directory listing, to ensure
consistency. The data is displayed to the user, and includes a
message such as "file is currently being downloaded, download will
be complete within xx seconds". Generally, the message is refreshed
by host device 100. In circumstances where host device 100 does not
refresh, the SD card forces a refresh every 2-3 seconds by a
refresh operation, or by a disconnect/connect operation using the
SD protocol.
[0070] Referring to FIG. 5B, in this embodiment the place holder
message "Please wait, file is downloading" from the stub file is
played to the user. It will be appreciated by those skilled in the
art the place holder messages may be displayed to a user as a still
image or video clip, or played as an audio file, or both. In one
embodiment, the place holder message is the same media type as the
file that is corresponds to; i.e., audio messages are played when
audio files are being downloaded, and video messages are played
when video files are being downloaded.
[0071] Referring to FIG. 5C, the file being downloaded is stored in
physical clusters 15, 16, 17, etc. This is reflected in the entry
for the "benny goodman" file in the download map, where cluster 15
is designated.
[0072] Referring back to FIG. 4, in general at step 445 application
290 receives the real file content and stores it in the flash
memory. The file is downloaded via communication modem 280. As it
arrives, application 290 updates the download map for the file with
the amount of data received, and updates the first cluster in the
cluster chain for the file in the flash memory. Each cluster of the
downloaded file is stored in a free cluster in the flash memory,
which is then marked as full. Thus it will be appreciated by those
skilled in the art that as the file is downloaded a regular file is
generated in the FAT, but without a directory item for the file.
Instead, the first sector of the file is stored in the download
map.
[0073] At step 450 host device 100 refreshes the file list. At step
455 a determination is made whether or not the download for the
file is complete. If not, processing returns to step 445 where
application 290 continues to download the file. Otherwise, if the
download is complete then, at step 460, application 290 marks the
last cluster of the downloaded file with an EOF.
[0074] At step 465, application 290 points the first cluster of the
file to the downloaded data cluster chain. Application 290 replaces
the directory entry for the file from the virtual cluster value to
the physical first cluster of the newly downloaded file. As such,
the file entry now points to a legitimate file. The file size is
also changed, so as to correspond to the received file length. The
file is then removed from the download map.
[0075] Referring to FIG. 5D, when host device 100 refreshes, the
user interface displays the new file, and the user listens to the
real Benny Goodman song. The downloaded file is now stored in
clusters 15-21, and cluster 21 is marked with an EOF. The
downloaded file now appears as a local file in the "jazz"
directory, and its entry is removed from the download map.
[0076] Reference is now made to FIG. 7, which is a simplified
flowchart of a method for playing a streamed file from an SD card,
in accordance with an embodiment of the present invention. At step
710, host device 100 accesses a media stub. At step 710 the stream
data associated with the media stub begins downloading, and is
dynamically stored in physical file clusters as it arrives, such as
file clusters 7-9 in FIG. 3. Application 290 waits until sufficient
data arrives to play a few seconds' worth of the media. Then, at
step 730, application 290 links the downloaded file to the FAT. The
file size is reported as being extremely long. At step 740,
application 290 continues to write new clusters of data, as the
stream if downloaded for several more seconds. At step 750, the FAT
cluster link becomes circular, and application 290 loops back to
the first stored cluster for the file.
[0077] In this regard, reference is now made to FIG. 8, which is an
illustration of file streaming using a circular cluster cycle in
the FAT, in accordance with an embodiment of the present invention.
The cross-hatched clusters in FIG. 8 correspond to the FAT legend
provided in FIG. 3.
[0078] Referring back to FIG. 7, at step 760 a determination is
made whether or not the user has stopped listening to the stream.
Such a determination may be made by application 290, by identifying
a lack of access by host device 100 to the file clusters. If the
user has not stopped listening to the stream, then processing
returns to step 740 as more data is streamed. Otherwise, if the
user has stopped listening to the stream then, at step 770,
application 290 updates the FAT to point to a stub in the virtual
memory, and frees up all clusters that have been designated for the
streamed file.
[0079] In addition to downloading of remote files to SD card 210,
application 290 may also upload files from SD card 210 to a remote
server, and store them in a designated directory. Application 290
may create a directory named "uploads" under the root directory,
when the file system of SD card 210 is initialized. The "uploads"
directory is generated as a directory list stub in the virtual
storage area, and includes a single data cluster. The "uploads"
directory is initially set as an empty directory.
[0080] Reference is now made to FIG. 9, which is a simplified
flowchart of a method for uploading a file from an SD card to a
remote server, in accordance with an embodiment of the present
invention. To accompany FIG. 9, reference is also made to FIGS. 10A
and 10B, which are snapshots of a user interface and a file system
for a simple example use case, during various stages of file upload
during operation of the method of FIG. 9. FIG. 10A is divided into
three portions. The leftmost portion illustrates a user interface,
the middle portion illustrates directory entries and the upload
map, and the rightmost portion illustrates the FAT. FIG. 10B is
divided into two portions. The left portion illustrates directory
entries and the upload map, and the right portion illustrates the
FAT. Thus, whereas FIG. 9 describes the steps being performed, the
accompanying FIGS. 10A and 10B illustrate states of the user
interface and the file system during various ones of the steps. The
legends for the cross-hatching on the FIGS. 10A and 10B are the
same as the legend provided in FIG. 3. It will be appreciated by
those skilled in the art that the file system illustrated in FIGS.
10A and 10B is simplified, in order to emphasize the workings of an
embodiment of the present invention.
[0081] Referring to FIG. 9, in general at step 910, when host
device 100 is instructed to upload a file to a remote server, it
creates a new file in a virtual directory named "uploads". At step
920, SD controller 250 identifies a write request to the "uploads"
directory. SD controller may identify such request, since host
device 100 issues the write request to a virtual cluster number. SD
controller then sends an event to application 290.
[0082] At step 930, the host's write request is re-directed to a
hidden sector that holds the "uploads" directory listing content.
Application 290 recognizes that a new file is being created in the
"uploads" directory, and it allows host device 100 to write the
file content. At step 940 the file content is written to the file
created in the "uploads" directory. The file itself is treated as a
regular file in the file system.
[0083] FIG. 10A corresponds to a stage where the upload directory
listing is displayed in the user interface, and a user has selected
a file name "recording.mp3" for upload. As shown in FIG. 10A, the
root directory has an entry for a stub uploads directory located at
virtual cluster 36. The root directory also has an entry for the
music file "recording.mp3", which is stored at clusters 1-6.
[0084] FIG. 10B corresponds to a stage where the selected file is
copied to the physical storage area, and the upload process begins.
Referring to FIG. 10B, there is now an "uploads" directory with an
entry for the file "recording.mp3" having first cluster 7.
[0085] At step 950, application 290 determines whether or not host
device 100 has finished writing the file and has closed the file.
If not, processing returns to step 940. If host device 100 has
closed the file, then at step 960 application 290 initiates a
communication session with the remote server, and at step 970
application 290 sends the file content to the remote server.
[0086] At step 980, application 290 determines whether or not the
file has been successfully delivered to the remote server. If not,
processing returns to step 970. If the file has been successfully
delivered to the remote server, then at step 990 the file is
removed from the file system and from the outgoing directory
listing.
[0087] In reading the above description, persons skilled in the art
will realize that there are many apparent variations that can be
applied to the methods and systems described. In particular, it
will be appreciated that the present invention applies to general
file systems, and is not restricted to FAT file systems.
[0088] In the foregoing specification, the invention has been
described with reference to specific exemplary embodiments thereof.
It will, however, be evident that various modifications and changes
may be made to the specific exemplary embodiments without departing
from the broader spirit and scope of the invention as set forth in
the appended claims. Accordingly, the specification and drawings
are to be regarded in an illustrative rather than a restrictive
sense.
* * * * *
References