User Manual

ThingMagic Nano User Guide 38
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Port Power and Settling Time
ThingMagic Nano allows the power and settling time for each logical antenna to be set using the reader
configuration parameters /reader/radio/portReadPowerList and /reader/antenna/settlingTimeList,
respectively.
NOTE: Settling time is the time between the control lines switching to the next antenna setting and RF
turning on for operations on that port. This allows time for external multiplexer’s to fully switch
to the new port before a signal is sent, if necessary. Default value is 0.
Tag Handling
When the ThingMagic Nano performs inventory operations (MercuryAPI Read commands) data is stored in
a Tag Buffer until retrieved by the client application, or data is streamed directly to the host if operating in
Tag Streaming/Continuous Reading mode.
Tag Buffer
ThingMagic Nano uses a dynamic buffer that depends on EPC length and quantity of data read. As a rule
of thumb, it can store a maximum of 48 96-bit EPC tags in the Tag Buffer at a time. Since ThingMagic Nano
supports streaming of read results, typically the buffer limit is not an issue. Each tag entry consists of a
variable number of bytes and the following fields:
The Tag buffer acts as a First In First Out (FIFO) — the first Tag found by the reader is the first one to be
read out. Duplicate tag reads do not result in additional entries - the tag count is simply incremented, and
the meta-data revised if necessary.
Tag Streaming/Continuous Reading
When reading tags during asynchronous inventory operations (MercuryAPI Reader.StartReading()) using
an /reader/read/asyncOffTime=0 ThingMagic Nano “streams” the tag results back to the host processor.
This means that tags are pushed out of the buffer as soon as they are put into the buffer by the tag reading
process. The buffer is put into a circular mode that keeps the buffer from filling. This allows for ThingMagic
Nano to perform continuous search operations without the need to periodically stop reading and fetch the
contents of the buffer. Aside from not seeing “down time” when performing a read operation, this behavior
is essentially invisible to the user as all tag handling is done by the MercuryAPI.
NOTE: The
TTL Level UART Interface does not support control lines, so it is not possible for the module
to detect a broken communications interface connection and stop streaming the tag results. Nor
can the host signal that it wishes tag streaming to stop temporarily without stopping the reading
of tags.
Tag Buffer
Total Entry Size Field Size Description
68 bytes
(Max EPC
Length = 496bits)
EPC
Length
2 bytes Indicates the actual EPC length of the tag read.
PC Word 2 bytes Contains the Protocol Control bits for the tag.
EPC 62 bytes Contains the tag’s EPC value.
Tag CRC 2 bytes The tag’s CRC.
Additional Tag Read Meta Data