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Carrier Board Design Guide for SOM-9X35 Module
65
4.14 MCU Interface
The SOM-9X35 module features an MCU interface.
4.14.1
MCU Signal Definition
The following table provides the definition of the MCU signals that are implemented in the M.2 slot.
Signal Name
Pin #
I/O
Pad Characteristics
Description
Voltage
Type
MCU_INT
J2.44
GPIO132
1.8V
I, PD
Interrupt input, High active, connect to MCU
MCU_WDI
J2.46
GPIO133
1.8V
I, PD
Watchdog feed output, High active, connect to MCU
MCU_STATUS
J2.50
GPPIO64
1.8V
I, PU
MCU status, Low: MCU upgrading; High: MCU work
SDA2
J1.7
GPIO61
1.8V
I, PU
I2C2 SDA, default connect to front camera and
MCU/I/O extender
SCL2
J1.9
GPIO62
1.8V
I, PU
I2C2 SCL, default connect to front camera and
MCU/I/O extender
Table 39: SOM-9X35 MCU signal definition
4.14.2
MCU Design Notes
It is highly recommended using the MCU to achieve the following functions:
•
System power management, watchdog timer, IR decoder, system suspend/wakeup, RTC timer, battery
charge status judgement, battery voltage ADC.
4.14.3
MCU Reference Schematics
WDT Control
MCU2CPU_INT
WDI
MCU_WDI
R201
22
STM_PB2
MCU_INT
R203
22
MCU_INT
STM_PC2
[5]
[5]
VCC_MCU
PWRON
[24]
STM_PC4
R206
10K_1%
R208
33
STM_PB7
STM_PC4
[25]
1V8_RTC
VCC_MCU
C317
4.7uF
16V
X6S
C311
10pF
C312
10pF
FB33
BLM15PX121SN1D
C315
0.01uF
16V
X7R
C318
0.1uF
16V
X7R
X2
32.768KHZ
1
2
R637
22
C316
0.1uF
16V
X7R
U20
STM8L151G4U6TR
NRST/PA1
1
PA2/OSC_IN/[USART1_TX]/[SPI1_MISO]
2
PA3/OSC_OUT/[USART1_RX]/[SPI1_MOSI]
3
PA4/TIM2_BKIN/[TIM2_ETR]/ADC1_IN2/COMP1_INP
4
PA5/TIM3_BKIN/[TIM3_ETR]/ADC1_IN1/COMP1_INP
5
VSS1/VSSA/VREF-
6
VDD1/VDDA/VREF+
7
PD0/TIM3_CH2/[ADC1_TRIG]/ADC1_IN22/COMP2_INP/COMP1_INP
8
PD1/TIM1_CH3/[TIM3_ETR]/ADC1_IN21/COMP2_INP/COMP1_INP
9
PD2/TIM1_CH1/ADC1_IN20/COMP1_INP
10
PD3/TIM1_ETR/ADC1_IN19/TIM1_BKIN/COMP1_INP/RTC_CALIB
11
PB0/TIM2_CH1/ADC1_IN18/COMP1_INP
12
PB1/TIM3_CH1/ADC1_IN17/COMP1_INP
13
PB2/TIM2_CH2/ADC1_IN16/COMP1_INP
14
PB3/[TIM2_ETR]/TIM1_CH1N/ADC1_IN15/RTC_ALARM/COMP1_INP
15
PB4/[SPI1_NSS]/ADC1_IN14/COMP1_INP/DAC_OUT
16
PB5/[SPI1_SCK]/ADC1_IN13/DAC_OUT/COMP1_INP
17
PB6/[SPI1_MOSI]/ADC1_IN12/COMP1_INP/DAC_OUT
18
PB7/[SPI1_MISO]/ADC1_IN11/COMP1_INP
19
PD4/TIM1_CH2/ADC1_IN10/COMP1_INP
20
PC0/I2C1_SDA
21
PC1/I2C1_SCL
22
PC2/USART1_RX/ADC1_IN6/COMP1_INP/VREFINT
23
PC3/USART1_TX/ADC1_IN5/COMP1_INP/COMP2_INM
24
PC4/USART1_CK/I2C1_SMB/CCO/ADC1_IN4/COMP2_INM/COMP1_INP
25
PC5/OSC32_IN/[SPI1_NSS]/[USART1_TX]
26
PC6/OSC32_OUT/[SPI1_SCK]/[USART1_RX]
27
PA0/[USART1_CK]/SWIM/BEEP/IR_TIM
28
STM_PB4
STM_PB6
STM_PB7
STM_SWIM
STM_PD1
STM_PD4
I2C_SDA_MCU
I2C_SCL_MCU
STM_RST
STM_OSC32_IN
STM_TX
STM_RX
STM_PB1
STM_PB2
STM_PC2
STM_PC4
STM_PB3
STM_PB0
STM_PB5
STM_PC3
STM_PA4
STM_PD0
STM_PD2
STM_PA5
STM_PD3
STM_OSC32_OUT
STM_RST
[15,24]
VCC_MCU
D13
LRB520S-30T1G
A
K
C319
0.1uF
16V
X7R
R211
10K_1%
STM_RST
VCC_MCU
4V6_RTC
R216
1.5M_1%
R215
1M_1%
R674
470K
R213
100K_1%/X
R214
1K_1%/X
STM_PC4
STM_PC3
STM_PD2
MCU_STATUS
Q25
LMBT3904TT1G
1
2
3
R204
10K_1%
STM_PB5
MCU OTA Upgrade Status
[5]
EN_4G_PWR
CHG_ENn
EN_MAIN_PWR
USB_DRVVBUS
R209
1K_1%
R205
1K_1%
R207
1K_1%
STM_PD1
EN_4G_PWR
STM_PB4
STM_PB1
EN_MAIN_PWR
STM_PD0
[18]
[5,18,19]
[6]
[9]
ACOK_CHG
STM_PB3
[18]
IR_INT
STM_PD3
[15]
(Ba�ery Charge Enable,Low ac�ve)
(MCU power on System)
MCU
Power on Key
Figure 80:
SOM-9X35 MCU IC reference circuitry