User's Manual
Table Of Contents
- Contents
- Figures
- Tables
- Document history
- Introduction
- Product concept
- GSM application interface
- GSM/GPRS operating modes
- Power supply
- Power up / down scenarios
- Automatic GPRS Multislot Class change
- Charging control of the GSM part
- Power saving
- Summary of state transitions (except SLEEP mode)
- RTC backup for GSM part of XT55/56
- Serial interfaces of the XT55/56 GSM part
- Audio interfaces
- SIM interface
- Control signals
- GPS application interface
- GSM and GPS antenna interfaces
- Electrical, reliability and radio characteristics
- Mechanics
- Reference approval
- Example applications
- List of parts and accessories
XT55/56 Hardware Interface Description
Confidential / Released
s
XT55/56_hd_v02.06a Page 58 of 125 17.12.2004
When shipped from factory, all audio parameters of XT55/56 are set to interface 1 and audio
mode 1. This is the default configuration optimized for the Votronic HH-SI-30.3/V1.1/0
handset and used for type approving the Siemens reference configuration. Audio mode 1 has
fix parameters which cannot be modified. To adjust the settings of the Votronic handset
simply change to another audio mode.
In transmit direction, all audio modes contain internal scaling factors (digital amplification)
that are not accessible by the user. To avoid saturation with a full scale digital input signal on
the DAI, and to obtain a one-to-one digital access to the speech coder in audio mode 5
and 6, it is recommended to set the parameter <inCalibrate> of the selected audio mode as
follows:
Audio mode 1 and 4: 23196
Audio mode 2: 17396
Audio mode 3: 21901
Audio mode 5 and 6: 21402
3.10.1 Microphone circuit
Interface 1
This interface has no microphone supply circuit and therefore, has an impedance of 50k
Ω.
When connecting a microphone or another signal source to interface 1 you are required to
add two 100 nF capacitors, one to each line.
Interface 2
This interface comes with a microphone supply circuit and can be used to feed an active
microphone. It has an impedance of 2k
Ω. If you do not use it or if you want to connect
another type of signal source, for example, an op amp or a dynamic microphone, it needs to
be decoupled with capacitors. The power supply can be switched off and on by using the
command AT^SNFM. For details see [1].
Figure 16 shows the microphone inputs at both analog interfaces of XT55/56.
2.65 V
to ADC
Power down
GSM_MICP1
GSM_MICN1
GSM_MICP2
GSM_MICN2
1 k 1 k
1
k
1
k
33
µ
F
Ri=50k
Ri=2k
Figure 16: Schematic of microphone inputs