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Carrier Board Design Guide for SOM-9X35 Module
63
•
The front and rear cameras must use different I2C whether the AF driver/sensor and driver/EEPROM's
I2C slave addresses are the same or not.
•
Route each I2C SDA/SCL Bus together and do not trace with other critical signals (MIPI or RF trace).
•
If the I2C device power domain is 2.5V or 3.3V, a level shift is required. (ex. G-sensor/Touch panel)
•
To avoid power leakage on the I2C Bus from the SOM-9X35 module to the carrier board, a diode is
required for the VDD on the level shift IC (CPU side).
I2C0 Bus Level S
hi�
1V8_VCC_I2C0
3V3_VCC
SCL0
[5,23]
SDA0
[5,23]
I2C_SCL_RPI
[23,25]
I2C_SDA_RPI
[23,25]
U58
ETA4553DCI/X
GND
4
B2
6
B1
7
VCCB
8
VCCA
1
A1
2
A2
3
OE
5
I2C0_OE
VCCA<=VCCB
1V8_VCC_I2C0
3V3_VCC
1V8_VCC
1V8_VCC
SCL0
[5,23]
I2C_SCL_RPI
[23,25]
SDA0
[5,23]
I2C_SDA_RPI
[23,25]
D59
LRB551V-30T1G
30V
0.5A
SOD-323
A
K
C630
0.1uF
16V X7R
R378
2K_1%
R373
15K_1%
U57
SGM4553YN8G/TR
VCCB
1
B1
2
B2
3
OE
4
GND
5
A2
6
A1
7
VCCA
8
R374
2K_1%
C626
0.1uF
16V X7R
I2C0_OE
Figure 77: SOM-9X35 I2C level shift IC reference circuitry
If an I2C Device & Host power is not present simultaneously when the system is suspended or powered off, a
level shift is required.
Note:
The N Channel MOS FET should be a fast switching type, the Vgs(th) gate-source threshold voltage should be less
than 1.65V.
I2C1 Bus Level S
hi�
Very fast switching
1V8_VCC_I2C1
1V8_VCC
1V8_VCC
1V8_VCC_I2C1
SCL1
[5,14]
I2C1_SCL
[14,17]
I2C1_SDA
SDA1
[5,14]
R685
0
R666
2K_1%
Q69
BSS138BKS
60V
320mA
TRANSISTOR DUAL N CHANNEL
S1
1
G1
2
D2
3
S2
4
G2
5
D1
6
D60
LRB551V-30T1G/X
30V
0.5A
SOD-323
A
K
C756
0.22uF
16V
X7R
R665
2K_1%
[14,17]
Figure 78: SOM-9X35 I2C level shift reference circuitry
4.13 UART & SPI Interface
The SOM-9X35 module features a SPI & two UART interfaces.
4.13.1
UART & SPI Signal Definition
The following table provides the definition of the UART & SPI signals that are implemented in the M.2 slot.
Signal Name
Pin #
I/O
Pad Characteristics
Description
Voltage
Type
URXD2
J2.36
GPIO39
1.8V
I, PD
UART2 RXD, default for NFC
UTXD2
J2.38
GPIO40
1.8V
I, PD
UART2 TXD, default for NFC
UTXD1
J2.40
GPIO38
1.8V
I, PD
UART1 TXD output, default connect to RS232 transceiver
URXD1
J2.42
GPIO37
1.8V
I, PD
UART1 RXD input, default connect to RS232 transceiver