Uart Application - Quectel NB-IoT Module Series Hardware Design

3.8.4. UART Application

The module provides 1.8V UART interfaces. A level translator should be used if the application is
equipped with a 3.3V UART interface. A level translator TXS0108EPWR provided by Texas Instruments is
recommended. The following figure shows a reference design.
Module
VDD_EXT
RXD
TXD
RXD_DBG
TXD_DBG
RXD_AUX
TXD_AUX
RI
GND
Please visit http://www.ti.com for more information.
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.
BC66_Hardware_Design
Module
TXD_AUX
RXD_AUX
GND
Figure 14: Reference Design for Auxiliary UART Port
VCCA
0.1uF
OE
A1
A2
A3
A4
A5
A6
A7
51K
A8
Figure 15: Reference Circuit with Translator Chip
DTE
TXD
RXD
GND
VCCB
0.1uF
GND
B1
B2
Translator
B3
B4
B5
B6
B7
51K
B8
NB-IoT Module Series
BC66 Hardware Design
DTE
VDD
TXD
RXD
TXD_DBG
RXD_DBG
TXD_AUX
RXD_AUX
GPIO
GND
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