EGS5 Hardware Interface Description
7 Sample Application
118
EGS5_HD_v02.004
Page 117 of 123
2012-02-09
Confidential / Released
7
Sample Application
shows a typical example of how to integrate EGS5 modules with a Java application.
Usage of the various host interfaces depends on the desired features of the application.
Audio interface 1 demonstrates the balanced connection of microphone and earpiece. This so-
lution is particularly well suited for internal transducers. Audio interface 2 uses an unbalanced
microphone and earpiece connection typically found in headset applications.
The charging circuit is optimized for the charging stages (trickle charging and software con-
trolled charging) as well as the battery and charger specifications described in
.
The PWR_IND line is an open collector that needs an external pull-up resistor which connects
to the voltage supply VCC µC of the microcontroller. Low state of the open collector pulls the
PWR_IND signal low and indicates that the EGS5 module is active, high level notifies the Pow-
er-down mode. If the module is in Power-down mode avoid current flowing from any other
source into the module circuit, for example reverse current from high state external control
lines. Therefore, the controlling application must be designed to prevent reverse flow.
If the I2C bus is active the two lines I2CCLK and I2DAT are locked for use as SPI lines. Vice
versa, the activation of the SPI locks both lines for I2C. Settings for either interface are made
by using the AT^SSPI command. The internal pull-up resistors (Rp) of the I2C interface can be
connected to an external power supply or to the VEXT line of EGS5. The advantage of using
VEXT is that when the module enters the Power-down mode, the I2CI interface is shut down
as well. If you prefer to connect the resistors to an external power supply, take care that the
interface is shut down when the PWR_IND signal goes high in Power-down mode.
The interfaces ASC0, ASC1 and USB have different functions depending on whether or not
Java is running. Without Java, all of them are used as AT interfaces. When a Java application
is started, ASC0 and ASC1 can be used for CommConnection or/and System.out, and the USB
lines can be used for debugging or System.out.
While developing SMT applications it is strongly recommended to provide test points
for certain signals resp. lines to and from the module - for debug and/or test purposes.
The SMT application should allow for an easy access to these signals. For details on
how to implement test points see
.
The EMC measures are best practice recommendations. In fact, an adequate EMC strategy for
an individual application is very much determined by the overall layout and, especially, the po-
sition of components. For example, mounting the internal acoustic transducers directly on the
PCB eliminates the need to use the ferrite beads shown in the sample schematic. However,
when connecting cables to the module’s interfaces it is strongly recommended to add appro-
priate ferrite beads for reducing RF radiation.
Disclaimer
No warranty, either stated or implied, is provided on the sample schematic diagram shown in
and the information detailed in this chapter. As functionality and compliance with na-
tional regulations depend to a great amount on the used electronic components and the indi-
vidual application layout manufacturers are required to ensure adequate design and operating
safeguards for their products using EGS5 modules.
