User guide

M80 EVB User Guide
M80_EVB_UGD_V1.2 - 24 -
3.6. Communication
M80 provides multi type communication ports, such as main UART, Auxiliary UART and Debug
UART port.
3.6.1. Main UART
When there is a communication between PC and the module through main UART port, a RS_232
level shifter must be inserted between them. The following picture is the reference design of
RS-232 level shifter. The main UART can be used for AT command, GPRS data, CSD FAX, etc.
Multiplexing function is supported on the main UART Port as well. For the design circuit of main
Port, please refer to document [2].
9
8
7
6
5
4
3
2
1
15
14
8
9
11
12
5
7
6
10
4
26
2
27
13
18
20
21
16
17
19
22
23
24
3
1
25
28
GND
TO PC serial port
SP3238
3V
GND
GND
T5OUT
/SHUTDOWN
V+
GND
V-
VCC
T4OUT
T2OUT
T3OUT
T1OUT
R3IN
R2IN
R1IN
/STATUS
3V
ONLINE
R1OUT
R2OUT
R3OUT
/R1OUT
GND
T5IN
T4IN
T3IN
T2IN
T1IN
C2+
C2-
C1-
C1+
MODULE
RXD
DTR
RTS
RI
CTS
TXD
DCD
Figure 23: Level match circuit
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