Tag Interface.PDF

The concept of a common control model for all tag readers is targeted towards a single interface for all embedded tag reader control and interface programs. We discovered that as we developed a wide range of tag readers certain functionality was common to all of them. We are attempting to develop a standard set of possible control commands that an external agent would need to be able to control and communicate with a given tag reader. As an example, in all of the tag readers (described in Reconfigurable Agile Tag Reader Technologies for Combined EAS and RFID Capability, (http://www.media.mit.edu/~kingpin/auto-id99.pdf), which appeared in the proceedings of the 2nd IEEE Workshop on Automatic Identification Advanced Technologies), there is the ability to scan over a part of the tag reader’s excitation frequency range with variable resolution. As a result, the ability to set the frequencies at which the scan starts and stops is necessary. Given that all the tag readers we have developed up till now have used microcontrollerbased control systems, defaults are set during the power-up cycle of the microcontroller. In the course of the tag reader’s use there is typically a need to change these values. In a similar fashion, there is other functionality that requires external control and is shared across all tag readers, and thus we were drawn to the idea of a standard tag reader interface. The communications and control channel (the means by which external agents interface with the tag reader) and the protocol (the channel-specific format used to transmit data) differ between tag reader implementations and applications. As an example, some tag readers use the Wiegand channel and protocol (for access control applications), while we have used the RS-232 channel and protocol in much of our tag reader development. A design goal for the interface is a set of tag reader commands that are independent of the channel and protocol. An external agent would use these to control various functions and request changes in the state of the tag reader’s control program. Currently the RS-232 serial protocol is the default channel used by our tag readers, as our microcontrollers come with hardware peripherals that implement that protocol. For applications that require multiple tag readers to interface with control programs that may reside on the same computer, the RS-232 channel fails to scale efficiently as the number of tag readers increases. The advent of cheap Ethernet connectivity has increased the Ethernet communication channel’s viability, and Ethernet scales much better than any serial protocol. As larger numbers of tag readers need to be connected to common information and/or data collection systems, such channels become increasingly attractive. We would like to utilize the same control commands and interface irrespective of the channel being used, which will allow changes to the communication channel beyond even Ethernet. A standard software interface simplifies the development of subsequent tag readers by providing a common command set, a subset of which could be implemented in any particular tag reader, depending on the capabilities of its hardware. Separating the design of the tag reader’s control structure from the hardware implementation allows us to develop a single robust control program (for a workstation) that would be able to control any tag reader and monitor its data visually. This approach has proven useful as applications have emerged that require multiple tag readers connected to a network without human intervention.