|
>>> в состоянии покоя на микрофонном входе нет напряжения.
Да - микрофон запитывается только при разговоре.
Насколько я помню - гарнитура - второй канал. А он есть у SIM900B, SIM900D и SIM908.
Первый рисунок - даташит чипсета, второй кусок схемы SIM900.
5.4.4 Headset / hook switch detection
The PNX4851 includes circuitry to facilitate the asynchronous detection of an audio subsystem change
including headset insertion and removal, and hook switch depression and release. The ST-Ericsson
Wireless system software provides a framework for detecting and servicing changes in the headset
configuration and hook switch status.
For example, prior to inserting a headset connector into an audio jack, the system software must enable
the detection circuit. When a headset is connected to the system, an interrupt is asserted. The software
services the interrupt and configures the audio subsystem to transition the current configuration to a
configuration based on the headset; see Figure 17.
This same circuit is used to detect and service the hook switch. A hook switch can be implemented by
utilizing a switch to short the microphone terminals. When the terminals are shorted, an interrupt is
asserted, and an interrupt service routine is called to service the hook switch. With this feature, the
functionality of the hook switch can be configured by software and can depend on the context supporting
multiple configurations. This approach also minimizes current consumption. By shorting the microphone
terminals, the hook switch function consumes approximately 500 μA. Alternative approaches that keep
the microphone biased for long periods of time lead to excessive current consumption and can shorten
battery life.
--------------------
Не можна втрачати надію. Не можна здаватися до останньої миті. Можливо саме вона, остання мить, принесе весну, яка стане початком нового життя.
|
SIM900b. Не определяет подъем трубки.
Apr 13 2011, 05:02
