Delimited Read Command for Efficient Data Access from Radio Frequency Identification (RFID) Tags

• US 20090322482A1
• Filed: 06/30/2008
• Published: 12/31/2009
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: SCHUESSLER, Frederick
• Granted Patent: US 8,598,990 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: H04Q 2209/47 using RFID associated with sensors
• CPC Class Codes: H04Q 2209/75 by polling or interrogating the sub-stations
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

Methods, and systems for efficiently reading data stored in an RFID tag memory are described. A delimited read command is issued by an RFID reader, causing a tag to truncate the data read-out process when a delimiter data pattern is detected in the stored data. Upon receipt of a delimited read command, a tag reads data until a delimiter pattern is detected. The tag determines whether the detected pattern is a valid delimiter pattern or a spurious one. If the detected pattern is a valid delimiter, the tag terminates the read process and transmits the data to the reader. The format of the delimiter pattern may be modified based on needs of a particular communications protocol or specific implementations.

Claims

1. A method for efficiently accessing stored data from radio frequency identification (RFID) tags, the method comprising:

transmitting a delimited read command that causes an RFID tag to cease reading data stored in tag memory when a delimiter pattern is detected in the stored data; and

receiving a response to the delimited read command from the RFID tag.

2. The method of claim 1, further comprising:

prior to the transmitting step, determining a configuration of the RFID tag.

3. The method of claim 2, wherein the transmitting step comprises:

transmitting a forward delimited read command, when the tag memory has a bottom-growing-up configuration.

4. The method of claim 2, wherein the transmitting step comprises:

transmitting a reverse delimited read command, when the tag memory has a top-growing-down configuration.

5. The method of claim 1, wherein the transmitting step comprises:

Transmitting a maximum read length limit, wherein the delimited read command causes an RFID tag to cease reading data stored in tag memory when the limit has been reached.

6. The method of claim 5, further comprising:

adjusting the limit based on the statistics of prior communications.

7. The method of claim 1, wherein the transmitting step comprises:

transmitting a specified delimiter pattern for the tag to detect.

8. A method for retrieving data from an RFID tag memory, comprising:

receiving a delimited read command including a memory start address location and a read direction;

reading data starting from the memory start address location in the read direction;

terminating the read process when a delimiter pattern is detected in the data being read; and

transmitting the read data.

9. The method of claim 8, further comprising after the terminating step:

determining if the delimiter pattern is a false delimiter pattern; and

continuing the read process if the detected delimiter pattern is a false delimiter pattern.

10. The method of claim 9, wherein the determining step further comprises:

determining whether the delimiter pattern occurs at a location where a valid data item is expected; and

marking the delimiter pattern as false when the delimiter pattern occurs at a valid data location.

11. The method of claim 8, further comprising:

continuing the read process if the detected delimiter pattern occurs within a locked block of memory.

12. A data structure embodied in a computer readable medium for optimized access of data items in a memory of a radio frequency identification tag by a reader that transmits a delimited read command, the data structure comprising:

a sequence of data objects encoded to prevent a false delimiter pattern within the sequence; and

a delimiter pattern following the sequence of data objects, wherein the delimiter pattern indicates an end of data stored in the tag memory.

13. The data structure of claim 12, wherein the data is formatted using packed object format.

14. The data structure of claim 12, wherein the delimiter pattern is a zero-valued zero byte.

15. The data structure of claim 12, wherein the delimiter pattern is an arbitrary sequence of one and zero bits.

16. A method for writing data to a radio frequency identification tag to allow for efficient access to the data by a reader, comprising:

receiving a set of data objects to be written to a tag memory;

encoding the set of data objects according to a predefined format;

adding a delimiter pattern at the end of the encoded data to form a data sequence to be written to the tag memory; and

writing the data sequence to the tag memory.

17. The method of claim 16, further comprising:

determining whether the encoded set of data objects includes a pattern within a data object which is identical to the delimiter pattern; and

altering the pattern within the data object in a predetermined manner if the pattern is identical to the delimiter pattern.

18. The method of claim 16, further comprising:

determining whether the delimiter pattern occurs within a block to be locked; and

adding padding to the set of data objects such that the delimiter pattern occurs at the start of the following block.