User's Manual

T-0000-0004-V2.1: Using Mozart II
T-0000-0004-V2.1: Using Mozart II Page: 12 / 24
RE2
ROTARY ENCODER
W1
1
CMN
2
W2
3
S1
4
S2
5
KP_W0
KP_W1
C48
470n
C49
470n
+3.3V
R51
10k
R52
10k
R53 100
R54 100
The module can support a 16x1 matrix of switches, each of the switches needs to be connected to
one row and to the KP_RET pin. Simultaneous presses are not supported, however short and long
presses detection is available.
7.2 UNDERSTANDING BUTTON MAPPING
It is important to understand that even if buttons can be changed inside the matrix for routing purposes
for instance, the real issue is the application itself. The logic of the application, eg the action of each
button in each user screen, is driving the number and function of the buttons – and changing this is not
easy at all, even if it might seem simple. Each button has a given function in all the possible states of
the application.
If the intended application does not use one of the standard software deliveries, we strongly
recommend to have the proposed scheme be validated by us since the software will require
customization – once again the physical organization is the smallest issue when it comes to UI/MMI
considerations. In all cases, provided that the number and meaning of buttons is the same, the matrix
can be layout any way – the software is easy to reconfigure for this matter.
8 Dealing with I2C
The I2C bus is used to control internal and external peripherals of the module. The following I2C
addresses are used by the module and external devices should not use them (apart from display of
course) :
• codec 0x1A
• FM 0x10
The lines should be kept short. If long wiring is needed because of the product configuration, it is
recommended to use an I2C buffer such as NXP’s PCA9515.
9 Dealing with Ethernet
The module has external connections for the TX and RX differential pairs in addition with link and
activity LEDs. In order for the signals to be kept in proper condition, care must be taken for the lines to
be routed with impedance matching (90 ohm differential) and with minimal length. The output
transformer can be integrated inside the connector or put apart. Activity LED signals can drive LEDs
directly (although a limiting resistor is needed); connect LED cathode to +3.3v
Ethernet is a known source of issues regarding EMC considerations. It is recommended to use high-
voltage capacitors of x2 class.
It is also recommended to use common-mode filters on the line. Some Ethernet transformers will
directly include those CMFs for easier integration.