Apalis Carrier Board Design Guide
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Figure 43: 8-bit MMC/SD Card Slot Reference Schematic
2.13.3 Unused SD/MMC/SDIO Interface Signal Termination
All unused SD interface signals can be left unconnected. If a complete SD/MMC/SDIO ports is
unused, the signal can be used as GPIO. Unused signals of a used port (for example the upper
four data bits of the 8-bit interface when used only in 4-bit mode), may be able to be used as
GPIO. Check the relevant Apalis module datasheet for more information.
2.14 I
2
C
The Apalis module standard features three I
2
C interfaces. The interface I2C1 is a general purpose
I
2
C while I2C2 is intended to be used with the DDC interface and I2C3 is intended to be used with
the camera interfaces. All I
2
C interfaces can also be used for general purpose.
The I
2
C as well as the DDC interfaces do not feature any pull-up resistors on the module. It is
required to add pull-up resistors to the data and clock lines on the carrier board. The pull-up
resistor value is typically between 1
Ω
and 10k
Ω
. A small pull-up resistor increases the power
consumption while a large resistor could lead to problems in the signal quality. The optimum size
of the resistor depends on the capacitive load on the I
2
C lines and the required bus speed.
2.14.1 I
2
C Signals
Apalis
Pin
Apalis
Signal Name
I/O
Type
Power
Rail
Description
209
I2C1_SDA
I/O
OD
3.3V
General purpose I
2
C data signal,
pull-up resistor required on carrier board
211
I2C1_SCL
O
OD
3.3V
General purpose I
2
C clock signal,
pull-up resistor required on carrier board
205
I2C2_SDA
I/O
OD
3.3V
Display Data Channel I
2
C data signal,
pull-up resistor required on carrier board
207
I2C2_SCL
O
OD
3.3V
Display Data Channel I
2
C clock signal,
pull-up resistor required on carrier board
201
I2C3_SDA
I/O
OD
3.3V
Camera interface I
2
C data signal,
pull-up resistor required on carrier board
203
I2C3_SCL
O
OD
3.3V
Camera interface I
2
C clock signal,
pull-up resistor required on carrier board
Table 24: I
2
C signals
2.14.2 Real-Team Clock (RTC) recommendation
The RTC on the module is not designed for ultra-low power consumption. Therefore, a standard
lithium coin cell battery can drain faster than allowed for certain designs. If a rechargeable RTC
battery is not a solution, it is recommended to use an external ultra-low power RTC IC on the
carrier board instead. In this case, add the external RTC to the I2C1 interface of the module and
leave the VCC_BACKUP pin unconnected.
101-00565-64
DAT2
15
DAT3
14
DAT4
13
CMD
12
DAT5
11
C/D
2
GND
10
VDD
9
CLK
8
DAT6
7
GND
6
DAT7
5
DAT0
4
DAT1
3
WP
1
MMC
8 b it
X18A
MMC1_D0
MMC1_D1
MMC1_D2
MMC1_D3
MMC1_D4
MMC1_D5
MMC1_D6
MMC1_D7
MMC1_CMD
MMC1_CLK
MMC1_CD#
10nF
25V
C40
R55
10K
GND
TP14
GND
GND
100nF
16V
C38
10uF
6.3V
C39
GND
2A
220R@100MHz
L11
3.3V_MMC
SD/MMC 8bit Holder
MM70-314-310B1
MMC1_CLK
154
Apalis - MMC
11 of 25
MMC1_CD#
164
MMC1_CMD
150
MMC1_D0
160
MMC1_D1
162
MMC1_D2
144
MMC1_D3
146
MMC1_D4
148
MMC1_D5
152
MMC1_D6
156
MMC1_D7
158
X1K
MXM3_150_M
MXM3_154_M
MXM3_164_M
MXM3_160_M
MXM3_162_M
MXM3_144_M
MXM3_146_M
MXM3_148_M
MXM3_152_M
MXM3_156_M
MXM3_158_M
R47
68K
R48
68K
R49
68K
R50
68K
R51
68K
R46
33K
R52
68K
R53
68K
R54
68K
3.3V_SW
3.3V_SW
3.3V_SW
101-00565-64
SHIELD
S1
S2
S3
S4
X18B
22R
RA18A
22R
RA18B
22R
RA16C
22R
RA16A
22R
RA16B
22R
RA18C
22R
RA16D
22R
RA20A
22R
RA18D
22R
RA20B
22R
RA20C
22R
RA20D
GND
GND
MMC1_D0
MMC1_D1
MMC1_D2
MMC1_D3
MMC1_D4
MMC1_D5
MMC1_D6
MMC1_D7
MMC1_CMD
MMC1_CLK
MMC1_CD#