Smart Machine Smart Decision
SIM800L(MT6261)_Hardware Design_V1.01 30 2016-07-07
1K
5.6K
RXD
TXD
RTS
CTS
GPIO
GPIO
EINT
DTE
(3.3V)
5.6K
5.6K
1K
1K
1K
1K
1K
1K
Module
TXD
RXD
RTS
CTS
DTR
DCD
RI
GND
GND
Figure 21: Resistor matching circuit
If the voltage of UART is 3V or3.3V, the following reference circuits are recommended:
TXD
RXD
Module DTE
TXD
RXD
VDD_EXT
10K
10K
GND
GND
Figure 22: Diode isolation circuit
Note: please make sure the minimum of client high limit should be less than 2.8V minus the diode drop.
If the voltage of UART is 5V, the following reference circuits are recommended:
VDD_EXT
4.7K
47K
TXD
4.7K
Module
VDD_EXT
RXD
VDD
DTE
Figure 23: TX level matching circuit
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