I65/I56I HARDWARE DESCRIPTION VERSION
1.00
5.7 Audio interface
The I56/I56i comprises an audio interface available on the 40-pin board-to-
board connector:
An analogue audio interface, with a balanced analogue microphone input
and a balanced analogue earpiece output.
5.7.1 Microphone
circuit
This interface with a microphone supply circuit and can be used to feed an
active microphone. It has an impedance of 50 k
Ω
.
5.8 Control signals
5.8.1 Synchronization
signal
The synchronization signal serves to indicate growing power consumption
during the transmit burst. The signal is generated by the GPIO1 pin. Please
note that this pin can adopt two different operating modes which you can select
by using the
AT^SGPIO1
command (mode 0 and 1). For details refer to the
following chapter and to [
]. To generate the synchronization signal the pin
needs to be configured to mode 0 (= default). This setting is recommended if
you want your application to use the synchronization signal for better power
supply control. Your platform design must be such that the incoming signal
accommodates sufficient power supply to the I56/I56i module if required. This
can be achieved by lowering the current drawn from other components
installed in your application. The timing of the synchronization signal is shown
below. High level of the GPIO1 pin indicates increased power consumption
during transmission.
Figure 16:
GPIO1 signal during transmit burst
*)
The duration of the GPIO1 signal is always equal, no matter whether the traffic
or the access burst are active
.
5.8.2 Using the GPIO1 pin to control a status LED
As an alternative to generating the synchronization signal, the GPIO1 pin can
be used to control a status LED on your application platform.
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