LTE Standard Module Series
EC200U_Series_Hardware_Design 43 / 94
MAIN_TXD
67
DO
Main UART transmit
MAIN_RXD
68
DI
Main UART receive
Table 16: Pin Definition of Debug UART Interface
Pin Name
Pin No.
I/O
Description
Comment
DBG_TXD
12
DO
Debug UART transmit
1.8 V power domain. If unused,
keep them open.
DBG_RXD
11
DI
Debug UART receive
Table 17: Pin Definition of Auxiliary UART Interface
Pin Name
Pin No.
I/O
Description
Comment
AUX_TXD
138
DO
Auxiliary UART transmit
1.8 V power domain. If unused,
keep them open.
AUX_RXD
137
DI
Auxiliary UART receive
The module provides 1.8 V UART interface. Use a level shifter if the application is equipped with a 3.3 V
UART interface. A level shifter TXS0108EPWR provided by
Texas Instruments
is recommended. The
following figure shows a reference design.
VCCA
VCCB
OE
A1
A2
A3
A4
A5
A6
A7
A8
GND
B1
B2
B3
B4
B5
B6
B7
B8
VDD_EXT
MAIN_RI
MAIN_DCD
MAIN_RTS
MAIN_RXD
MAIN_DTR
MAIN_CTS
MAIN_TXD
51K
51K
0.1
μ
F
0.1
μ
F
RI_MCU
DCD_MCU
RTS_MCU
TXD_MCU
DTR_MCU
CTS_MCU
RXD_MCU
VDD_MCU
Translator
1
0
K
120K
Figure 20: Reference Circuit with Translator Chip
Please visit http://www.ti.com for more information.
Another example with transistor circuit is shown as below. For the design of circuits shown in dotted lines,
see that shown in solid lines, but pay attention to the direction of connection.
