NB-IoT Module Series
BC66 Hardware Design
BC66_Hardware_Design 28 / 57
VCCA
VCCB
OE
A1
A2
A3
A4
A5
A6
A7
A8
GND
B1
B2
B3
B4
B5
B6
B7
B8
VDD_EXT
TXD
RXD
TXD_DBG
RXD_AUX
RXD_DBG
TXD_AUX
51K
51K
0.1uF
0.1uF
TXD
RXD
TXD_DBG
RXD_AUX
RXD_DBG
TXD_AUX
VDD
Translator
RI*
GPIO
Module
DTE
GND
GND
Figure 17: Reference Circuit with Voltage Level Translator Chip
Another example with transistor translation circuit is shown as below. The circuit design of dotted line
section can refer to the design of solid line section, in terms of both module input and output circuit
designs, but please pay attention to the direction of connection.
DTE
VDD_EXT
10K
VCC_DTE
4.7K
10K
VDD_EXT
Module
VDD_EXT
4.7K
1nF
1nF
RXD
TXD
TXD_DBG
RXD_DBG
TXD_AUX
RXD_AUX
GPIO
GND
GND
RXD_DBG
TXD_DBG
RXD_AUX
TXD_AUX
RI*
TXD
RXD
Figure 18: Reference Circuit with Transistor Circuit
The following circuit shows a reference design for the communication between the module and a PC with
standard RS-232 interface. Please make sure the I/O voltage of level shifter which connects to module is
1.8V.