Quectel BC66 - Page 32

NB-IoT Module Series
BC66 Hardware Design
BC66_Hardware_Design 31 / 59
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
GNDGND
RXD_DBG
TXD_DBG
RXD_AUX
TXD_AUX
RI
TXD
RXD
Figure 19: 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.
TXD
RXD
RI
Module
GND
C1+
C1-
C2+
C2-
V+
VCC
GND
V-
3.3V
T1IN
T2IN
T3IN
T4IN
R1IN
R2IN
R3IN
R1OUT
R2OUT
R3OUT
T1OUT
T2OUT
T5OUT
T3OUT
T4OUT
T5IN
GND
GND
/R1OUT
1
2
3
4
5
7
8
9
GND
To PC Main Serial Port
GND
RS-232
Transceiver
6
Level Shifter
(1.8V~3.3V)
Figure 20: Sketch Map for RS-232 Interface Match
Please visit vendors’ websites to select a suitable RS-232 transceiver, such as: http://www.exar.com and
http://www.maximintegrated.com.