A New Method ofHigh Speed P2P File Transfer
using SD Card and TransferJet
TechnologyWhite Paper | September 2014www.sdcard.org | ©2014 SD Association. All rights reserved

Conditions for publication
Publisher and Copyright Holder:
SD Card Association
2400 Camino Ramon, Suite 375
San Ramon, CA 94583 USA
Telephone: +1 (925) 275-6615,
Fax: +1 (925) 886-4870
E-mail: office@sdcard.org

Disclaimers:
The information contained in this whitepaper is provided AS-IS without any representations or warranties of any kind. No
responsibility is assumed by the SD Association for any damages, or any infringements of patents or other rights of the SD
Association or any third parties, which may result from the use of any portion thereof. No license is granted by implication,
estoppel or otherwise under any patent or other rights of the SD Association or any third party. Nothing herein shall be
construed as an obligation by the SD Association to disclose or distribute any technical information, know-how or otherconfidential information to any third party.
TransferJet regular typeface and TransferJet logos are trademarks licensed by TransferJet Consortium.

Trademarks Notice:
SD is a trademark or a registered trademark of SD-3C, LLC in the United States, other countries or both.

A New Method of High Speed P2P File Transfer using SD Card and TransferJet Technology

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www.sdcard.org | ©2014 SD Association. All rights reserved1Table of Contents
1.
2.

3.

4.

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42.2 Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2.2.1 OBEX Peer-to-Peer File Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2.2.2 SCSI Mass Storage Class Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5iSDIO TransferJet System Model and Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
3.1 iSDIO TransferJet Interface Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63.2 Directory and File Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7SD Association2400 Camino Ramon, Suite 375
San Ramon, CA 94583 USA
Telephone: +1 (925) 275-6615,
Fax: +1 (925) 886-4870
E-mail: help@sdcard.org

A New Method of High Speed P2P File Transfer using SD Card and TransferJet Technology

3www.sdcard.org | ©2014 SD Association. All rights reserved11. Executive Summary
The size of user generated content such as photos and videos is becoming larger and larger these days due to the increase in
the total number of shots taken as well as the advent of super high resolution video formats such as 4K video, using consumerdevices such as digital still cameras, camcorders and smartphones.
This global market trend naturally generates a need for high-speed peer-to-peer file transfer without requiring any special
knowledge or skills in network configuration, but designed with the ultimate in ease of use.
The iSDIO TransferJet Addendum was developed to address these market requirements by utilizing TransferJet, which is a
close proximity, high speed wireless data transfer technology.
TransferJet has various unique properties, including 1) advanced ease of use, 2) physical security, and 3) robust datatransmission. More detailed information about the TransferJet Technology can be found at:
http://www.transferjet.org/tj/tj_overview.html
The iSDIO TransferJet Addendum enables the creation of TransferJet-equipped iSDIO cards, which allow data stored in thecards to be transferred to other TransferJet-equipped devices by means of simple, high-level instructions.
This will also dramatically reduce the implementation efforts needed for the iSDIO host devices.

2. Introduction
2.1 Overview
The iSDIO TransferJet card is an intelligent SDIO combo card that incorporates a TransferJet communication module and aflash memory module. Both modules in the card are able to communicate with each other using simple instructions froman iSDIO host. As an example, data recorded in the iSDIO TransferJet card inserted in an SD host device can be sent toanother TransferJet enabled device such as a PC, a smartphone, a printer or other iSDIO TransferJet card using theTransferJet communication channel.

2.2 Use Cases
The iSDIO TransferJet card will provide value-added features to SD cards for the following two use cases, 1) OBEX Peer-toPeer File Transfer, and 2) SCSI Mass Storage Class Drives. Note that OBEX means OBject EXchange, a protocol of datatransmission.
2.2.1 OBEX Peer-to-Peer File Transfer
The OBEX Peer-to-Peer File Transfer is a mandatory function within the set of TransferJet protocols.
In this use case, an OBEX Sender card sends file(s) to another OBEX Receiver card. These cards may reside inside a PC,
smartphone, network attached storage (NAS), printer or kiosk terminal, where at least one of the two devices is anOBEX Sender or OBEX Receiver.
Figure 2-1 shows the outline of this use case.

A New Method of High Speed P2P File Transfer using SD Card and TransferJet Technology

4www.sdcard.org | ©2014 SD Association. All rights reserved1Figure 2-1: OBEX Peer-to-Peer File Transfer

2.2.2 SCSI Mass Storage Class Drive
The SCSI Mass Storage Class Drive is an optional implementation of the TransferJet protocols.
In this case, a SCSI Target card is mounted on the File System of a SCSI Initiator device.
Actual user scenarios will depend on the application of the SCSI Initiator but the SCSI Target card will in general simply
behave as an external storage device connected to the SCSI Initiator device.
The SCSI Initiator may be a PC or printer, but is not limited to these devices.
Figure 2-2 shows the outline of this use case.

Figure 2-2: SCSI Mass Storage Class Drive

A New Method of High Speed P2P File Transfer using SD Card and TransferJet Technology

5www.sdcard.org | ©2014 SD Association. All rights reserved

13. iSDIO TransferJet System Model and Functions
3.1 iSDIO TransferJet Interface Model
Figure 3-1 shows the “iSDIO TransferJet Card Interface and Network Interface” between a card and host device. Thehighlighted blocks are defined within the iSDIO TransferJet Addendum.
See also the TransferJet Overview, available at: http://www.transferjet.org/tj/transferjet_overview.pdf

Figure 3‑1: iSDIO TransferJet Card Interface and Network Interface

Figure 3‑2: iSDIO TransferJet Card Interface and Card System Model

A New Method of High Speed P2P File Transfer using SD Card and TransferJet Technology

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www.sdcard.org | ©2014 SD Association. All rights reserved13.2 Directory and File Structure
The iSDIO TransferJet Addendum defines the directory and file structures necessary to maintain interoperability and datatransfer.
Figure 3-3 shows an example of the directory and file structures in the iSDIO TransferJet card.
CONFIG FILE stores certain parameters which may be used when a TransferJet connection or an application is started, if thecard provides the CONFIG FILE features.
In the OBEX Peer-to-Peer File Transfer, the OBEX Sender host creates a list of files to be sent to the OBEX Receiver card, andstores the list in the designated directory.
Then the OBEX Sender card will send the FILELIST file followed by data in the file(s) to be sent to the OBEX Receiver card.
The FILELIST file may be used by the OBEX Receiver host to calculate/display the transmission progress. The FILELIST file
may also be used by the OBEX Sender/Receiver hosts to determine the resume point of disrupted transaction in the eventof transmission disruption occurred.
ROOT: Root directory of an iSDIO Card

: Directory defined in DCF

DCIM

SD_TJET: Directory defined in iSDIO TransferJet

P2P: Directory for OBEX Peer-to-Peer File Transfer

CONFIG: Configuration fileFILELIST: File List fileFigure 3-3: Example of Directory and File Structure

4. Conclusion
The iSDIO TransferJet Addendum will provide another option of wireless communication technologies for consumers. The
advanced, intuitive ease of use enabled by TransferJet technology will benefit consumers who need high performance yetcannot handle complicated configuration procedures of wireless systems.
It is difficult for any single technology to satisfy all the different market requirements. The iSDIO standard is designed toexpand and accommodate new and future market requirements. This TransferJet Addendum will enable the implementationof new usage models and applications based on the iSDIO standard.

A New Method of High Speed P2P File Transfer using SD Card and TransferJet Technology7

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