Product Info

LTE Standard Module Series
EC25 Hardware Design
EC25_Hardware_Design 52 / 112
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 90Ω.
 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 on not only upper
and lower layers but also right and left sides.
 Pay attention to the influence of junction capacitance of ESD protection components on USB data
lines. Typically, the capacitance value should be less than 2pF.
 Keep the ESD protection components to the USB connector as close as possible.
1. EC25 module can only be used as a slave device.
2. “*” means under development.
3.11. 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 4800bps, 9600bps, 19200bps, 38400bps, 57600bps, 115200bps,
230400bps, 460800bps and 921600bps baud rates, and the default is 115200bps. The interface is
used for data transmission and AT command communication.
 The debug UART interface supports 115200bps baud rate. It is used for Linux console and log
output.
The following tables show the pin definition of the UART interfaces.
Table 11: Pin Definition of Main 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
CTS 64 DO Clear to send
RTS 65 DI Request to send
NOTES