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VT-SBC-3399 | User Manual 17
2.4.7
J21 RS232 & RS485 (7)
VT-SBC-3399 offers 2 RS232 connectors and 1 RS485 connector. One RS232 connector
(UART4) has its signal derived from the CPU, corresponding to device node ttyS4. The other
RS232 connector and RS485 connector are expanded from an independent chipset,
corresponding to device nodes ttyACM1 and ttyACM0. JP1 is for connection of a 120
Ω
termination resistor for RS485.
J21 specification: MOLEX: 53261-1071, 1 x 10, 1.25mm
JP1 specification: NSXD: MEA1-03PBAA1, 1 x 3, 2mm
J21 pinout description:
Pin
Name
Type
Description
1
UART4_T
O
RS232_1 data output
2
UART4_R
I
RS232_1 data input
3
GND
P
Ground
4
RS485_A
I/O
RS485 Bus2 I/O port, A
5
RS485_B
I/O
RS485 Bus2 I/O port, B
6
GND
P
Ground
7
UARTB_T
O
RS232_2 data output
8
UARTB_R
I
RS232_2 data input
9
GND
P
Ground
10
NC
NC
JP1 pinout description:
Pin
Name
Type
Description
1
485_A_1
RS485 Bus1 I/O port A, connecting
120
Ω
resistor
2
485_B_1
RS485 Bus1 I/O port B
3
NC
NC
1
J21
UART4
RS485
RS232
JP1
1
