BLUEBOX Gen.2 HFM
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The incoming data packets to the ‘master’ assume the following structure:
Header
1° Byte
2° Byte
Max 14 Byte
7
6
5
4
3
2
1
0
Length
Data
Ack tx
Req rx
More
Busy
Reply Ack
Reply Nak
Tag present
Alive (toggle)
Also the incoming data packet consists of a header (first two bytes) and a data
buffer of 14 bytes in this example.
The first byte of the header consists of the following flags:
•
Bit 7: Alive, toggles every second and means that the ‘slave’ is running
correctly
•
Bit 6: Tag present, set to ‘1’ by the ‘slave’ means that a transponder is
present near the antenna/s (detected by the ‘continuous’ identification
activity)
•
Bit 5: Reply Nak, set to ‘1’ by the ‘slave’ means that an error has
occured
•
Bit 4: Reply Ack, set to ‘1’ by the ‘slave’ means that the received
command has been processed
•
Bit 3: Busy, set to ‘1’ by the ‘slave’ means that the ‘slave’ is processing
the command message from the ‘master’
•
Bit 2: More, set to ‘1’ by the ‘slave’ means that the message is composed
of several data packets
•
Bit 1: Req rx, reception request (from ‘slave’)
•
Bit 0: Ack tx, transmission acknowledge
The second byte (Length) of the header specifies the number of data bytes in
the data buffer (max 14 data bytes).
The messages consist of one or more data packets. If the length of the
message is shorter than 14 bytes, the message will be composed of only 1
data packet. If the length of the message is bigger than 14 bytes, the message
will be composed of more than 1 data packet; in this case the header of all the
transmitted data packets, apart the last one, will present at ‘1’ the flag ‘More’
