User's Manual Part 1

Sensor Board description
Wireless Sensing Triple Axis Reference design, Rev. 0.9
24 Freescale Semiconductor
Figure 3-7ZSTAR antenna layout
The matching is provided by L3 (transmit antenna) and L4 (receive antenna) coils. L1 and L2 coils bias
the transmitter output transistors to the V
DDA
level.
The inductors used in this design are from TDK:
L3 (5.6nH) MLG1608B5N6DT
L4 (4.7nH) MLG1608B4N7ST
and L1, L2 (22nH) MLG1608B22NJT.
3.4.8 Clocking options of MC9S08QG8
Due to the availability of accurate timing provided by the MC13191 transceiver, an internal oscillator (ICG)
in the MC9S08QG8 is used as the main clock source for the microcontroller. The protocol related timing
is derived from MC13191 timers, the microcontroller itself is clocked from an internal oscillator, leaving
the oscillator pins as GPIO. This is highly beneficial to the limited pin count microcontroller.
3.4.9 LED indicators connections
The MC13191 allows extension to the number of general I/O pins by 7 additional GPIO connections. Two
of these (GPIO1 and GPIO2) are used for LED indicators. R8 and R9 are their current limiting resistors,
and in the actual design orange LED’s are used, with a threshold voltage around 2.0-2.5V.
The remaining unused GPIO3-GPIO7 signals are connected to ground, improving the physical PCB
layout of the MC13191.