Service Guide

LTE Standard Module Series
EG915U_Series_Hardware_Design 49 / 90
Table 17: Pin Definition of Main UART Interface
Table 18: Pin Definition of Debug UART Interface
Table 19: Auxiliary UART Interface
The module provides 1.8 V UART interfaces. 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.
Pin Name
Pin No.
I/O
Description
Comment
MAIN_CTS
36
DO
DTE clear to send signal to
DCE (connect to DTE’s CTS)
1.8 V power domain.
If unused, keep them
open.
MAIN_RTS
37
DI
DTE request to send signal to
DCE (connect to DTE’s RTS)
MAIN_RXD
34
DI
Main UART receive
MAIN_DCD
38
DO
Main UART data carrier detect
MAIN_TXD
35
DO
Main UART transmit
MAIN_RI
39
DO
Main UART ring indication
MAIN_DTR
30
DI
Main UART data terminal ready
Pin Name
Pin No.
I/O
Description
Comment
DBG_RXD
22
DI
Debug UART receive
1.8 V power domain.
If unused, keep them open.
DBG_TXD
23
DO
Debug UART transmit
Pin Name
Pin No.
I/O
Description
Comment
AUX_TXD
27
DO
Auxiliary UART transmit
1.8 V power domain.
If unused, keep them open.
AUX_RXD
28
DI
Auxiliary UART receive