LTE Standard Module Series
EC200T Series Hardware Design
EC200T_Series_Hardware_Design 44 / 90
A common mode choke L1 is recommended to be added in series between the module and customer’s
MCU in order to suppress EMI spurious transmission. Meanwhile, the 0
Ω
resistors (R3 and R4) should
be added in series between the module and the test points so as to facilitate debugging, and the resistors
are not mounted by default. In order to ensure the integrity of USB data line signal, L1, R3 and R4
components must be placed close to the module, and also resistors R3 and R4 should be placed close to
each other. The extra stubs of trace must be as short as possible.
The following principles should be complied with when design the USB interface, so as to meet USB 2.0
specification.
It is important to route the USB signal traces as differential pairs with total grounding. The impedance
of USB differential trace is 90
Ω
.
Do not route signal traces under crystals, oscillators, magnetic devices and RF signal traces. It is
important to route the USB differential traces in inner-layer of the PCB, and surround the traces with
ground on that layer and ground planes above and below.
Please pay attention to the selection of the ESD component on the USB data line. Its parasitic
capacitance should not exceed 2 pF and should be placed as close as possible to the USB interface.
3.10. UART
Interfaces
The module provides two UART interfaces: the main UART interface and the debug UART interface. The
following shows their features.
The main UART interface supports 4800 bps, 9600 bps, 19200 bps, 38400 bps, 57600 bps, 115200
bps, 230400 bps, 460800 bps, 921600 bps and 1 Mbps baud rates, and the default is 115200 bps.
This interface is used for data transmission and AT command communication. Also, it supports RTS
and CTS hardware flow control.
The debug UART interface supports 115200 bps baud rate. It is used for the output of partial logs.
The following tables show the pin definition of main UART interface.
Table 13: Pin Definition of Main UART Interface
Pin Name
Pin No.
I/O
Description
Comment
MAIN_RI 62 DO
Main UART ring
indication
1.8 V power domain.
If unused, keep it open.
MAIN_DCD 63
DO
Main UART data carrier
detect
MAIN_CTS
64
DO
Main UART clear to send