Huawei ME909 Series - Circuit Recommended for the UART Interface

HUAWEI ME909 Series LTE LGA Module
Hardware Guide
Description of the Application Interfaces
Issue V0.3 (2013-05-21)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
32
Pin
No.
Pin Name
I/
O
Description
DC Characteristics (V)
Min.
Typ.
Max.
4
UART1_RX
I
UART1 receive data input
–0.3
1.8
2.1
28
UART2_TX
O
UART2 transmit output
–0.3
1.8
2.1
29
UART2_RX
I
UART2 receive data input
–0.3
1.8
2.1
3.5.2 Circuit Recommended for the UART Interface
Figure 3-13 Connection of the UART interface in the ME909 module (DCE) with the host
(DTE)
The RS-232 chip can be used to connect the ME909 module with UART. In this
connection, the Complementary Metal Oxide Semiconductor(CMOS) logic level and
the Electronic Industries Association (EIA) level are converted mutually. For example,
it is recommended that you use the MAX218 chip (The MAX218’s max baud is
120000 bit/s) with a 2-wire serial port.

It is recommended that customer set the pins related to UART interface as test points on the
DTE board for debugging.

The UART0_RX, UART0_TX, UART1_RX, UART1_TX, and UART2_RX, UART2_TX must
be pulled down. When you want the module is in sleep status, all the UART interface will be
in low level. Therefore, UART0_RX, UART0_TX, UART1_RX, UART1_TX and UART2_RX,
UART2_TX must be pulled down in order to confirm they are in low logic when the module is
in sleep status.

The level of RS-232 Transceivers must match that of the ME909 module.