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Coin-type rechargeable battery is recommended, such as XH414H-IV01E from Seiko can be used.
Typical charge-discharge curves for this battery are shown in the following figure.
Figure 21: Seiko XH414H-IV01E charge-discharge characteristic
4.6 Serial Port and USB Interface
SIM808 provides one unbalanced asynchronous serial port. The module is designed as a DCE (Data
Communication Equipment). The following figure shows the connection between module and client (DTE).
Table 10: Serial port and USB pin definition
Name Pin number Function
DTR 9 Data terminal ready
RI 10 Ring indicator
DCD 11 Data carrier detect
CTS 12 Clear to send
RTS 13 Request to send
TXD 14 Transmit data
Serial port
RXD 15 Receive data
VBUS 25 USB power supply
USB_DP 26 USB data line plus
USB
interface
USB_DM 27 USB data line minus
Note: Hardware flow control is disabled by default. The AT command “AT+IFC=2,2” can enable hardware flow control .The AT
command “AT+IFC=0,0”can disable hardware flow control. For more details, please refer to document [1].
Table 11: Serial port characteristics
Symbol Min Max Unit
V
IL
0 0.3 V
V
IH
2.5 2.8 V
V
OL
0 0.1 V
V
OH
2.7 2.8 V
SIM808_Hardware Design_V1.00 2014.03.27
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