Fastrack Supreme User Guide
Functional Description
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RES ET m od e
I
B B + RF
= 2 0 t o
4 0 m A
~ RES ET
ST A T E O F T H E
W ireles s CP U
W ireles s
CPU
REA D Y
Rt = M in
1
: 2 0 0
μ
s
or T y p
2
= 4 0 m s
A T an sw ers “ O K”
W ireles s CP U
REA D Y
SIM an d n et w o r k
d ep en d en t
W ireles s CP U
O N
I
B B + RF
< 1 2 0 m A
w it h o u t lo c u p d at e
Ct = T y p : 3 4 m s
Figure 17: Reset sequence diagram
7.8
Audio
Audio interface is a standard one for connecting a phone handset.
Echo cancellation and noise reduction features are also available to improve the audio quality in case of
hand-free application.
7.8.1
Microphone Inputs
The microphone inputs are differential ones in order to reject common mode noise and TDMA noise.
They already include the convenient biasing for an electret microphone (0.5 mA and 2 Volts) and are ESD
protected.
This electret microphone may be directly connected to these inputs allowing an easy connection to a
handset.
The microphone impedance must be around 2 k
Ω
.
AC coupling is already embedded in the Wireless CPU
®
.
The gain of the microphone inputs is internally adjusted and may be tuned from 30 dB to 51 dB using an
AT
+VGT
command (refer to AT commands documentation [6]).
Pin description
Signal
Sub D 15-pin
Pin #
I/O
I/O type
Description
CMIC2P
4
I
Analog
Microphone positive input
CMIC2N
5
I
Analog
Microphone negative input
