Gemalto M2M TC65 Users Manual

TC65 Hardware Interface Description

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3.11.1 Installing the USB Modem Driver

This section assumes you are familiar with installing and configuring a modem under
Windows 2000 and Windows XP. As both operating systems use multiple methods to access
modem settings this section provides only a brief summary of the most important steps.

Take care that the “usbmodem.inf” file delivered with TC65 is at hand. Connect the USB
cable to the TC65 host application (for example the evaluation board DSB75) and the PC.
Windows detects TC65 as a new USB modem, opens the
reports that it is searching for the “Siemens AG WM USB Modem” driver. Follow the
instructions on the screen and specify the path where the “usbmodem.inf” file is located.
Windows will copy the required software to your computer and configure the modem by
assigning a free COM port. If you are already using more than one COM port then the next
free one will be allocated. Click

Notes for Windows 2000 only:

• During the installation procedure you will be prompted for the “usbser.sys” driver. Make
sure the file is present before you start installing the above inf file.
The “usbser.sys” file is not delivered as a single file, but must be extracted from a
Windows 2000 cabinet file. This is either the file “driver.cab” located in the “I386” folder of
the original Windows 2000 CD or a later cabinet file inside the Service Pack. SP4 for
example includes the “sp4.cab” file which can be found in its “I386” folder. The
“usbser.sys” driver from the Service Pack has priority over one provided with the
standard Windows 2000 install CD.

• It is necessary to restart Windows 2000 to make the changes take effect.

Finish to complete the installation.

Found New Hardware Wizard and

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You can find the “Siemens AG WM
USB Modem” listed under

Panel

| Phone and Modem Options |

Modems.

Troubleshooting for installation problems

If Windows fails to
assign the next free
COM port to TC65 and,
for example, allocates a
COM port already used
by another modem you
can manually select a
free port as follows:

Open the Windows

Device Manager, select

the installed “Siemens
AG WM USB Modem”,
click

Properties, select

the

Advanced tab and

click

settings

listbox

Number

port. To make the
changes take effect
disconnect and re­connect the USB cable.
If not yet successful,
also restart Windows.

Advanced Port

. From the

COM Port

choose a free

Control

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3.12 I2C Interface

I2C is a serial, 8-bit oriented data transfer bus for bit rates up to 400kbps in Fast mode. It
consists of two lines, the serial data line I2CDAT and the serial clock line I2CCLK.

The TC65 module acts as a single master device, e.g. the clock I2CCLK is driven by module.
I2CDAT is a bi-directional line.

Each device connected to the bus is software addressable by a unique 7-bit address, and
simple master/slave relationships exist at all times. The module operates as master­transmitter or as master-receiver. The customer application transmits or receives data only
on request of the module.

To configure and activate the I
two lines I2CCLK and I2DAT are locked for use as SPI lines. Vice versa, the activation of the
SPI locks both lines for I
explanations on the protocol and syntax required for data transmission can be found in [1].

2

The I

C interface can be powered from an external supply or via the VEXT line of TC65. If
connected to the VEXT line the I
enters the Power-down mode. If you prefer to connect the I
supply, take care that VCC of the application is in the range of V
shut down when the PWR_IND signal goes high. See figures below as well as Section 7 and
Figure 38.

In the application I2CDAT and I2CCLK lines need to be connected to a positive supply
voltage via a pull-up resistor.

For electrical characteristics please refer to Table 17.

2

C bus use the AT^SSPI command. If the I2C bus is active the

2

C. Detailed information on the AT^SSPI command as well

2

C interface will be properly shut down when the module

2

C interface to an external power

and that the interface is

VEXT

GSM module

I2CDAT
I2CCLK
GND

Application

VCC

R

p

Figure 15: I2C interface connected to VCC of application

R

p

I2CDAT
I2CCLK
GND

w

VEXT

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GSM module

VEXT

I2CDAT
I2CCLK
GND

R

p

Application

R

p

I2CDAT
I2CCLK
GND

Figure 16: I2C interface connected to VEXT line of TC65

Note: Good care should be taken when creating the PCB layout of the host application: The

traces of I2CCLK and I2CDAT should be equal in length and as short as possible.

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3.13 Audio Interfaces

TC65 comprises three audio interfaces available on the board-to-board connector:

• Two analog audio interfaces, both with balanced or single-ended inputs/outputs.

• Serial digital audio interface (DAI) designed for PCM (Pulse Code Modulation).

This means you can connect up to three different audio devices, although only one interface
can be operated at a time. Using the AT^SAIC command you can easily switch back and
forth.

MICP1

MICN1

MUX

VMIC

AGND

USC0

USC1

USC2

USC3
USC4

USC5

USC6

MICP2

MICN2

EPP1

EPN1

EPP2

EPN2

MUX

Digital
Audio
Interface

Analog switch

Figure 17: Audio block diagram

D

D

DSP

Ai
Interface

To suit different types of accessories the audio interfaces can be configured for different
audio modes via the AT^SNFS command. The electrical characteristics of the voiceband part
vary with the audio mode. For example, sending and receiving amplification, sidetone paths,
noise suppression etc. depend on the selected mode and can be altered with AT commands
(except for mode 1).

Both analog audio interfaces can be used to connect headsets with microphones or
speakerphones. Headsets can be operated in audio mode 3, speakerphones in audio
mode 2. Audio mode 5 can be used for a speech coder without signal pre or post processing.

When shipped from factory, all audio parameters of TC65 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.

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3.13.1 Speech Processing

The speech samples from the ADC or DAI are handled by the DSP of the baseband
controller to calculate e.g. amplifications, sidetone, echo cancellation or noise suppression
depending on the configuration of the active audio mode. These processed samples are
passed to the speech encoder. Received samples from the speech decoder are passed to
the DAC or DAI after post processing (frequency response correction, adding sidetone etc.).

Full rate, half rate, enhanced full rate, adaptive multi rate (AMR), speech and channel
encoding including voice activity detection (VAD) and discontinuous transmission (DTX) and
digital GMSK modulation are also performed on the GSM baseband processor.

3.13.2 Microphone Circuit

TC65 has two identical analog microphone inputs. There is no on-board microphone supply
circuit, except for the internal voltage supply VMIC and the dedicated audio ground line
AGND. Both lines are well suited to feed a balanced audio application or a single-ended
audio application.

The AGND line on the TC65 board is especially provided to achieve best grounding
conditions for your audio application. As there is less current flowing than through other GND
lines of the module or the application, this solution will avoid hum and buzz problems.

3.13.2.1 Single-ended Microphone Input

Figure 18 as well as Figure 38 show an example of how to integrate a single-ended
microphone input.

VMIC

R

R

A

V

Bias

R

A

C

F

R

B

VMIC

MICPx

GSM module

MICNx

C

K

AGND

Figure 18: Single ended microphone input

R

has to be chosen so that the DC voltage across the microphone falls into the bias voltage

A

range of 1.0V to 1.6V and the microphone feeding current meets its specification.

The MICNx input is automatically self biased to the MICPx DC level. It is AC coupled via C
to a resistive divider which is used to optimize supply noise cancellation by the differential
microphone amplifier in the module.

RA = typ. 2k
R

= typ. 5k

B

R

= typ. 470Ohm

VMIC

C

= typ. 100nF

k

= typ. 22µF

C

F

V

= typ. 2.5V

MIC

V

= 1.0V … 1.6V, typ. 1.5V

bias

K

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The VMIC voltage should be filtered if gains larger than 20dB are used. The filter can be
attached as a simple first order RC-network (R

and CF).

VMIC

This circuit is well suited if the distance between microphone and module is kept short. Due
to good grounding the microphone can be easily ESD protected as its housing usually
connects to the negative terminal.

3.13.2.2 Differential Microphone Input

Figure 19 shows a differential solution for connecting an electret microphone.

VMIC

R

VMIC

R

A

MICPx

C

F

GSM module

RA = typ. 1k
R

= 470Ohm

VMIC

C

= typ. 100nF

K

C

= typ. 22µF

F

V

= typ. 2.5V

MIC

V

= 1.0V … 1.6V, typ. 1.5V

bias

MICNx

V

Bias

R

A

C

K

AGND

Figure 19: Differential microphone input

The resulting DC voltage between MICPx and AGND should be in the range of 1.0V to 1.6V
to bias the input amplifier. MICNx is automatically self biased to the MICPx DC level. The
resulting AC differential voltage is then amplified in the GSM module.

The VMIC voltage should be filtered if gains larger than 20dB are used. The filter can be
attached as a simple first order RC-network (R

and CF).

VMIC

The advantage of this circuit is that it can be used if the application involves longer lines
between microphone and module.

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3.13.2.3 Line Input Configuration with OpAmp

Figure 20 shows an example of how to connect an opamp into the microphone circuit.

VMIC

R

C

K

R

VMIC

A

MICPx

~

R

C

K

C

F

A

MICNx

V

Bias

GSM module

AGND

Figure 20: Line input configuration with OpAmp

RA = typ. 47k
R

= 470Ohm

VMIC

C

= typ. 100nF

k

= typ. 22µF

C

F

V

= typ. 2.5V

MIC

V

= typ. ½ V

bias

= 1.25V

MIC

The AC source (e.g. an opamp) and its reference potential have to be AC coupled to the
MICPx resp. MICNx input terminals. The voltage divider between VMIC and AGND is
necessary to bias the input amplifier. MICNx is automatically self biased to the MICPx DC
level.

The VMIC voltage should be filtered if gains larger than 20dB are used. The filter can be
attached as a simple first order RC-network (R

and CF). If a high input level and a lower

VMIC

gain are applied the filter is not necessary.

If desired, MICNx via C

can also be connected to the inverse output of the AC source

K

instead of connecting it to the reference potential for differential line input.

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3.13.3 Loudspeaker Circuit

The GSM module comprises two analog speaker outputs: EP1 and EP2. Output EP1 is able
to drive a load of 8Ohms while the output EP2 can drive a load of 32Ohms. Each interface
can be connected in differential and in single ended configuration. See examples in Figure
21 and Figure 22.

Loudspeaker impedance

EPP1/EPN1

= typ. 8Ohm

Z

L

EPPx

GSM module

EPNx

EPP2/EPN2
Z

= typ. 32Ohm

L

AGND

Figure 21: Differential loudspeaker configuration

EPPx

GSM module

EPNx

AGND

Loudspeaker impedance

EPP1/EPN1
Z

= typ. 8Ohm

L

C

= 220µF

k

EPP2/EPN2

= typ. 32Ohm

Z

L

C

= 47µF

k

+

C

k

Figure 22: Single ended loudspeaker configuration

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3.13.4 Digital Audio Interface DAI

TBD

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3.14 Control Signals

3.14.1 Synchronization Signal

The synchronization signal serves to indicate growing power consumption during the transmit
burst. The signal is generated by the SYNC pin (pin number 32). Please note that this pin
can adopt three different operating modes which you can select by using the AT^SSYNC
command: the mode AT^SSYNC=0 described below, and the two LED modes AT^SSYNC=1
or AT^SSYNC=2 described in [1] and Section 3.14.2.

The first function (factory default AT^SSYNC=0) 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
TC65 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 SYNC pin
indicates increased power consumption during transmission.

1 Tx 577 µs every 4.616 ms
2 Tx 1154 µs every 4.616 ms

Transmit burst

SYNC signal

*)

The duration of the SYNC signal is always equal, no matter whether the traffic or the

*)

t = 180 sµ

Figure 25: SYNC signal during transmit burst

access burst are active.

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3.14.2 Using the SYNC Pin to Control a Status LED

As an alternative to generating the synchronization signal, the SYNC pin can be configured
to drive a status LED that indicates different operating modes of the TC65 module. To take
advantage of this function the LED mode must be activated with the AT^SSYNC command
and the LED must be connected to the host application. The connected LED can be operated
in two different display modes (AT^SSYNC=1 or AT^SSYNC=2). For details please refer to
[1].

Especially in the development and test phase of an application, system integrators are
advised to use the LED mode of the SYNC pin in order to evaluate their product design and
identify the source of errors.

To operate the LED a buffer, e.g. a transistor or gate,
must be included in your application. A sample circuit
is shown in Figure 26. Power consumption in the LED
mode is the same as for the synchronization signal
mode. For details see Table 17, SYNC pin.

Figure 26: LED Circuit (Example)

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4 Antenna Interface

The RF interface has an impedance of 50Ω. TC65 is capable of sustaining a total mismatch
at the antenna connector or pad without any damage, even when transmitting at maximum
RF power.

The external antenna must be matched properly to achieve best performance regarding
radiated power, DC-power consumption, modulation accuracy and harmonic suppression.
Antenna matching networks are not included on the TC65 PCB and should be placed in the
host application.

Regarding the return loss TC65 provides the following values in the active band:

Table 11: Return loss in the active band

State of module Return loss of module Recommended return loss of application

Receive > 8dB > 12dB

Transmit not applicable > 12dB

The connection of the antenna or other equipment must be decoupled from DC voltage. This
is necessary because the antenna connector is DC coupled to ground via an inductor for
ESD protection.

4.1 Antenna Installation

To suit the physical design of individual applications TC65 offers two alternative approaches
to connecting the antenna:

• Recommended approach: U.FL-R-SMT antenna connector from Hirose assembled on

the component side of the PCB (top view on TC65). See Section 4.3 for details.

• Antenna pad and grounding plane placed on the bottom side. See Section 4.2.

The U.FL-R-SMT connector has been chosen as antenna reference point (ARP) for the
Siemens reference equipment submitted to type approve TC65. All RF data specified
throughout this manual are related to the ARP. For compliance with the test results of the
Siemens type approval you are advised to give priority to the connector, rather than using the
antenna pad.

IMPORTANT: Both solutions can only be applied alternatively. This means, whenever an
antenna is plugged to the Hirose connector, the pad must not be used. Vice versa, if the
antenna is connected to the pad, then the Hirose connector must be left empty.

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Antenna connected to Hirose connector:

Module

Antenna or
measurement

PAD

50Ohm

U.FL

equipment

50Ohm

Antenna connected to pad:

Module

PAD

50Ohm

s

U.FL

Z

Z

50Ohm

Figure 27: Never use antenna connector and antenna pad at the same time

ntenna

No matter which option you choose, ensure that the antenna pad does not come into contact
with the holding device or any other components of the host application. It needs to be
surrounded by a restricted area filled with air, which must also be reserved 0.8mm in height.

U.FL antenna connector

RF section

PCB

ntenna pad

Restricted area

Figure 28: Restricted area around antenna pad

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4.2 Antenna Pad

The antenna can be soldered to the pad, or attached via contact springs. For proper
grounding connect the antenna to the ground plane on the bottom of TC65 which must be
connected to the ground plane of the application.

When you decide to use the antenna pad take into account that the pad has not been
intended as antenna reference point (ARP) for the Siemens TC65 type approval. The
antenna pad is provided only as an alternative option which can be used, for example, if the
recommended Hirose connection does not fit into your antenna design.

Also, consider that according to the GSM recommendations TS 45.005 and TS 51.010-01 a
50Ω connector is mandatory for type approval measurements. This requires GSM devices
with an integral antenna to be temporarily equipped with a suitable connector or a low loss
RF cable with adapter.

Notes on soldering:

• To prevent damage to the module and to obtain long-term solder joint properties you are

advised to maintain the standards of good engineering practice for soldering.

• Be sure to solder the antenna core to the pad and the shielding of the coax cable to the

ground plane of the module next to the antenna pad. The direction of the cable is not
relevant from the electrical point of view.

TC65 material properties:
TC65 PCB: FR4
Antenna pad: Gold plated pad

4.2.1 Suitable Cable Types

For direct solder attachment, we suggest to use the following cable types:

• RG316/U 50Ohm coaxial cable

• 1671A 50Ohm coaxial cable

Suitable cables are offered, for example, by IMS Connector Systems. For further details and
other cable types please contact http://www.imscs.com

.

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