Quectel UC15, Hardware Design, Page: 35 / 73

UMTS/HSDPA Module
UC15 Hardware Design
UC15_Hardware_Design Confidential / Released 34 / 72
Figure 15: 5V level match circuit
The following picture is an example of connection between module and PC. A RS232 level shifter IC or
circuit must be inserted between module and PC, since these three UART ports do not support the RS232
level, while support the CMOS level only.
TXD
RXD
RTS
CTS
DTR
RI
DCD
Module
GND
C1+
C1-
C2+
C2-
28
25
1
3
V+
VCC
GND
V-
3V
27
2
26
4
T1IN
T2IN
T3IN
T4IN
R1IN
R2IN
R3IN
R1OUT
R2OUT
R3OUT
T1OUT
T2OUT
T5OUT
T3OUT
T4OUT T5IN
ONLINE /STATUS
/SHUTDOWN
SP3238
GND
GND
/R1OUT
24
23
22
19
17
16
21
20
18
13
14
10
6
7
5
12
8
9
11
15
1
2
3
4
5
6
7
8
9
GND 3V
To PC Serial Port
GND
Figure 16: RS232 level match circuit