User's Manual Part 2

ZSTAR RF protocol
Wireless Sensing Triple Axis Reference design, Rev. 0.9
Freescale Semiconductor 39
5.3.1.1 Network number
The network number is randomly generated at the beginning of the connection between the USB stick
and the Sensor Board. It is used to determine between various connections. Packets with different
Network numbers are simply ignored.
This field is 16 bits long.
5.3.1.2 RX strength
This field reports the strength of the last received packet on the other end of the connection. This value
simply tells us how well the other side receives ‘our packets’. This can be used by transmission power
management functions to change the transmission power if the other party receives packets with enough
strength.
The values reported are retrieved using the MLMELinkQuality() SMAC primitive.
This field is 8 bits long.
5.3.1.3 Zcommand
The ZSTAR demo protocol uses a few simple commands to establish and maintain the data flow between
the Sensor Board and USB stick.
The command is carried in
Zcommand field and is 8 bits long. The commands are defined as listed in
Table 5-1.
5.3.1.4 Zdata
The Zdata field follows the Zcommand field and may be empty if the actual command doesn’t require any
additional data. The data format is dependent on the
Zcommand. A detailed description is in the next
chapter.
Table 5-1ZSTAR
Zcommand List
ZCommand
ZCommand
code
Direction Zdata
ZSTAR_BROADCAST
‘B’ (0x42) USB stick to Sensor Board none
ZSTAR_ACK
‘A’ {0x41) USB stick to Sensor Board none
ZSTAR_CALIB
‘K’ (0x4B) USB stick to Sensor Board calibration data to Sensor Board
ZSTAR_STATUS
‘S’ (0x53) USB stick to Sensor Board g-range selection data to Sensor Board
ZSTAR_CONNECT
‘C’ (0x43) Sensor Board to USB stick calibration data from Sensor Board
ZSTAR_DATA
‘D’ (0x44) Sensor Board to USB stick
accelerometer values,
button levels,
g-range selection