User's Manual

LTE Module Series
EC21 Hardware Design
EC21_Hardware_Design Confidential / Released 43 / 94
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 4800, 9600,19200,38400,
57600,115200,230400,460800,921600and 3000000bps baud rates, and the default is 115200bps.
The interface is used for data transmission and AT command communication.
 The debug UART interface supports 115200bpsbaud rate. It is used forLinux console and log output.
The following tables show the pin definition of the main UART interface.
Table 11: Pin Definition of the 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
DTR 66 DI Sleep mode control
TXD 67 DO Transmit data
RXD 68 DI Receive data
Table 12: Pin Definition of the Debug UART Interface
Pin Name Pin No. I/O Description Comment
DBG_TXD 12 DO Transmit data
1.8V power domain
DBG_RXD 11 DI Receive data
The logic levels are described in the following table.