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X503U Reference Manual V3.2
2 Connectors Description
2.1 Serial connector
Function
Serial port connector
marking
Serial
Type
DB9 interface
Pin define
Pin 1 location: The green frame on the right.
The UART0 and UART1 serial ports are both 3.3V TTL logic level.
The mapping files in Linux system are respectively ttyS0 and
ttyTHS2 in /dev directory.
By default, UART0 is a kernel debugging serial port, which is used
to output c-boot, U-boot, and Linux kernel information. After the
Linux kernel is started, UART0 is used as a display terminal serial
port. TX1/TX2 default serial port setting is: 115200bps, 8N1.
Pin
Signal
Pin
Signal
1
NC
2
UART0 TX
3
UART0 RX
4
NV
5
GND
6
UART1 TX
7
UART1 RX
8
NC
9
GND
2.2 GPIO/I2C
and button connector
Function
GPIO
、
I2C
and button connection
marking
GPIO/I2C
Type
DB9 interface
Pin define
Pin
Signal
Pin
Signal
1
GPIO0
2
GPIO1
3
GPIO2
4
GPIO3
5
GND
6
I2C CLK
7
I2C SDA
8
RECOVERY BUTTON
9
POWER BUTTON
