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according to the actual situation.
Module
MAIN_TXD
RI
MAIN_RXD
VIO_SEL
GND
Figure 14: Reference Design for Module-PC Communication via RS-232 Interface
Please visit vendors' websites to select a suitable RS-232 transceiver, such as http://www.exar.com and
http://www.maximintegrated.com.
NOTES
1.
If the voltage domain of your application system is 1.8 V, keep the R1 in
3.3 V, keep the R1 in
"
" represents the test points of UART interfaces. It is recommended to reserve the test points of
2.
VBAT, BOOT and RESET_N for convenient firmware upgrade and debugging when necessary.
3.
MAIN_RXD cannot be pulled up to VDD_EXT directly. To pull up MAIN_RXD to VDD_EXT, you
need to connect a Schottky diode in series first, and then add a pull-up resistor of 4.7–20 kΩ. For
more details, see document [3].
When VIO_SEL is grounded and VBAT ˂ 3.3 V, VDD_EXT = VBAT;
1)
4.
When VIO_SEL is grounded and VBAT ≥ 3.3 V, VDD_EXT = 3.3 V;
When VIO_SEL is floating, VDD_EXT = 1.8 V.
When the serial port voltage is neither 1.8 V nor 3.3 V, it is recommended to use a level conversion circuit.
For the design of the circuit shown in the dotted line, refer to that shown in the solid lines, and pay
attention to the connection direction. In this case, the design of RI – GPIO circuit can refer to that of the
MAIN_TXD – RXD circuit.
BC660K-GL_Hardware_Design
C1+
C1-
C2+
C2-
T1IN
T2IN
T3IN
T4IN
T5IN
R1OUT
R1OUT
R2OUT
R1
R3OUT
0 Ω
RS-232
Transceiver
red
mounted.
BC660K-GL Hardware Design
V+
GND
GND
GND
VCC
3.3 V
V-
GND
T2OUT
T1OUT
T5OUT
To PC Main Serial Port
T3OUT
T4OUT
R1IN
R2IN
R3IN
NB-IoT Module Series
1
6
2
7
3
8
4
9
5
GND
red
not mounted; if it is
29 / 57
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