User's Manual

Smart Machine Smart Decision

SIM868_Hardware_Design_V1.00 27 2016-06-20

 Rechargeable battery backup

Figure 17: RTC supply from rechargeable battery

4.5. Serial Port and USB Interface

SIM868 default provides one unbalanced asynchronous serial ports. The module is designed as a DCE (Data

Communication Equipment). The following figure shows the connection between module and client (DTE).

Table 9: Serial port and USB pin definition

Note: Hardware flow control is disabled by default. AT command “AT+IFC=2, 2”can enable hardware flow

control. AT command “AT+IFC=0,0”can disable hardware flow control. For more details please refer to

document [1].

Table 10: Serial port characteristics

Symbol Min Max Unit

-0.3 0.7 V

2.1 3.1 V

- 0.4 V

Pin name Pin number

Function

Serial port

UART1_DTR 6 Data terminal ready

UART1_RI 7 Ring indicator

UART1_DCD 5 Data carrier detect

UART1_CTS 4 Clear to send

UART1_RTS 3 Request to send

UART1_TXD 1 Transmit data

UART1_RXD 2 Receive data

UART2_TXD 22 Transmit data

UART2_RXD 23 Receive data

GPS_TXD 61 Transmit data

GPS_RXD 62 Receive data

Debug port

USB_VBUS 24 USB power supply

USB_DP 25 D+ data input/output

USB_DM 26 D- data input/output