Uart Interfaces - Quectel BC66 Manual

4.8. UART Interfaces

The UART interfaces of BC66/BC660K-GL have different voltage domains, as listed below.
Table 8: UART Interface Voltage Domain
Module UART Interface
Main UART
BC66 Debug UART
AUX UART
Main UART
BC660K-GL
Debug UART
A compatible voltage level translation reference design for BC66/BC660K-GL's UART interfaces is shown
below. For designs of the circuits in dotted lines, refer to those in solid lines, and pay attention to the
direction of connection.
BC66/BC660K-GL
RXD
TXD
DBG_RXD
DBG_TXD
RXD_AUX
TXD_AUX
Figure 13: Compatible Reference Design for Level Conversion Circuits
BC66&BC660K-GL_Compatible_Design
VDD_EXT
10 kΩ
MAIN_RXD
MAIN_TXD
DBG_RXD
DBG_TXD
RI
RI
R2
VIO_SEL
NM_0 Ω
GND
BC66&BC660K-GL Compatible Design
R1
D1
1 nF
VDD_EXT
VCC_DTE
4.7 kΩ
NB-IoT Module Series
Voltage Domain
1.8 V
1.8/3.3 V
DTE
TXD
RXD
10 kΩ
DBG_TXD
DBG_RXD
TXD_AUX
RXD_AUX
GPIO
GND
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