User Guide

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GM500-U1G_A
Hardware Development Guide
2.10. UART Interface
The module provides two UART interfaces: Main UART Port and Debug UART Port. The Main UART Port can work in full function
mode while the Debug UART Port is used for software debugging . The following show the different features.
Main UART interface support 1200 2400 4800 9600 19200 38400 57600 115200 230400 460800 921600 1000000 1500000
2000000 2500000 3000000 3500000bps baud rate, the default is 115200bps, This interface can be used for data transmission; AT
communication or firmware upgrade (upgrade is not supported currently).
Debug UART interface supports 115200bps baud rate. It can be used for software debug and firmware upgrade. The module is
designed as the DCE (Data Communication Equipment), following the traditional DCE-DTE (Data Terminal Equipment) connection.
The following tables show the pin definition of these two UART interfaces.
Table 2-12Pin Definition of the Main UART Interface
Pin Name Pin NO. I/O Description Comment
UART_RI 60 DO Ring indicator 1.8V power domain
UART_DCD 59 DO Data carrier detection 1.8V power domain
UART_CTS 56 DI Clear to send 1.8V power domain
UART_RTS 55 DO Request to send 1.8V power domain
UART_DTR 58 DI Data terminal ready 1.8V power domain.
UART_DSR 57 DO Data set ready 1.8V power domain.
DO not pull-up external.
UART_TXD 53 DO Transmit data 1.8V power domain
UART_RXD 54 DI Receive data 1.8V power domain
Table 2-13Pin Definition of the Debug UART Interface
Pin Name Pin NO. I/O Description Comment
UART_DEBUG_TXD 68 DO Transmit data 1.8V power domain
UART_DEBUG_RXD 67 DI Receive data 1.8V power domain
2.10.1. UART CONNECTION
Three normal connections for UART are shown in the figures below:
1. 8-wires UART connection mode, mainly used for MODEM mode(PPP dialing for example)
TX D
RX D
RTS
CTS
DTR
DCD
RING
TXD
RX D
RTS
CTS
DTR
DCD
RING
Serial Port Serial Port
(DCE) (DTE)
DS R DS R
GND GND