User's Manual

LTE Module
EC20 Hardware Design
EC20_Hardware_Design Confidential / Released 37 / 83
In order to ensure the USB interface design corresponding with the USB 2.0 specification, please comply
with the following principles.
 It is important to route the USB signal traces as differential pairs with total grounding. The impedance
of USB differential trace is 90ohm.
 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 with ground shielding not only upper and
lower layer but also right and left side.
 Pay attention to the influence of junction capacitance of ESD component on USB data lines. Typically,
the capacitance value should be less than 2pF.
 Keep the ESD components as close as possible to the connector.
 Keep USB data test points traces short to avoid noise coupled on USB data lines. If possible, reserve
0R resistor on these two lines.
EC20 module can only be used as a slave device.
3.11. UART Interface
The module provides two UART interfaces: main UART interface and debug UART interface. The
following shows the different features.
 Main UART interface supports 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600bps
baud rate, the default is 115200bps. This interface can be used for data transmission and AT
communication.
 Debug UART interface supports 115200bps. It can be used for Linux console, log and GNSS NMEA
output.
The following tables show the pin definition.
Table 11: Pin Definition of the UART Interface
Pin Name
Pin No.
I/O
Description
Comment
RI
62
DO
Ring indicator
1.8V power domain
DCD
63
DO
Data carrier detection
1.8V power domain
CTS
64
DO
Clear to send
1.8V power domain
NOTE