ThingMagic Autonomous Configuration Tool - Manual (Page 23)

Processing Data from the Reader
Autonomous Configuration Tool v1.0 User Guide 23
Message Types Sent By Reader
When operating in autonomous mode there are three different messages that the reader
will send: Tag Read Data, Temperature Status (acts as keep-alive in GPI triggered read
mode) and Read-cycle reset/Keep-alive. The message types can be differentiated by
their Data Length field.
These messages contain the following data:
Tag Read Data Message
Table 5: Tag Read Data Packet Format
Field Value Description
Header (Hdr) 0xFF Defines the start of the packet.
Data Length (Len) [1 byte] Defines the length, M, of the data field contained in the
packet. Length value will be 0x10 to 0xFE
OpCode 0x22 Autonomous reader message
Status Word 0x0000 Since Tag Read Data messages only occur with successful
tag reads the status for these should always be 0x0000
RFU [7 bytes] Reserved for future use. Data can be ignored
RSSI [1 byte] Return Signal Strength Indicator
Antenna ID [1 byte] Antenna ID, 4 MSBs for TX and 4 LSBs for RX
Frequency [3 bytes] Frequency in kHz at which the tag was read
Timestamp [4 bytes] Millisecond offset from last Read-Cycle Reset/Keep-Alive
when tag was read.
Phase [2 bytes] Phase of signal tag was read at (0-180)
Protocol ID 0x05 Protocol ID of tag read 0x05 = Gen2/ISO18000/6C
Embedded Tag
Data Length [2 byte] Length, in bits, of the embbeded tag data read for this tag.
This value indicates how many bytes (ceiling[bits/8]), up to
32, will follow.
Example:
if the value is 0x1D (29) then 4 bytes will follow:
29/4 = 3.625 -- ceiling(3.625) = 4.
Tag Data [N bytes] Number of bytes of tag data as specified in Tag Data Length