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SIM800_Hardware Design_V1.10 31 2018-08-13
Note: when a diode used to isolate voltage cross, customer should notice that there’s voltage drop on the diode.
And the signal’s voltage level should meet the customer’s electrical character. The recommend diode is
Schottky diode e.g. RB551V-30TE-17 and SDM20U40.
If the voltage of UART is 5V on customer side, customer can use the following reference circuits:
VDD_EXT
4.7K
47K
UART1_TXD
4.7K
Module
VDD_
EXT
RXD
VDD
DTE
Figure 22: TX level converting by transistor
VDD_EXT
4.7K
47K
4.7K
DTE
UART1_RXD
Module
VDD_EXT
TXD
VDD
Figure 23: RX level converting by transistor
Note: The recommend Transistors’ part numbers are 2SC4617TLR and PBHV8115Z.
4.5.3 USB Interface
USB interface supports software debug function. When power on the module, connect USB_VBUS, USB_DP,
USB_DN and GND to PC, then install the driver successfully, a UART port could be recognized by the PC,
customer could achieve the software Debug purpose with this UART port.
The following diagram is recommended:
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