User's Manual Part 1

USB stick board description
Wireless Sensing Triple Axis Reference design, Rev. 0.9
28 Freescale Semiconductor
Figure 4-2USB stick board block diagram
Figure 4-3 shows, in more detail, how different software and hardware modules co-operate with each
other. There are two main tasks of the USB stick board:
• receive the data from the MC13191 transceiver and store it in RAM buffer
• handle the USB module communication, decode and provide the data from the RAM buffer
These two are somewhat independent and the only common point between them is the accelerometer
and button data buffer in RAM. The RF software communicates with the Sensor Board and retrieves the
latest accelerometer data. This is stored in RAM and can be independently read by the PC application via
the USB link. The protocol employed on the PC side is just a subset of the simple STAR protocol used in
the original RD3112MMA7260Q demo. The protocol is described in chapter
5.4 STAR protocol and
ZSTAR extensions (over USB)
.
MCHC908JW32
MCU
MC13191
2.4GHz RF
receive antenna
transmit antenna
SPI
IRQ
ATTN
RST
RXTXEN
USB
+5V USB
voltage
regulators
+5V USB