User Guide

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GM500-U1G_A
Hardware Development Guide
Figure 2–17Schematic of 8-wire UART Connection
2. 3-wire UART connection:
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
Figure 2–18 Schematic of 3-wire UART Connection
3. 4-wire UART connection, with hardware flow control:
TX D
RX D
RTS
CTS
DTR
DCD
RING
TX D
RX D
RTS
CTS
DTR
DCD
RING
Serial Port Serial Port
(DCE) (DTE)
DS R DS R
GND GND
Figure 2–19 Schematic of 4-wire UART Connection
2.10.2. UART LEVEL MATCH
Notice the level match when connect module to external MCU. Level must be less than 3.0V under normal operation, and its
default speed rate is 115200 bps.
We recommend to use audion or IC for UART level match circuit. The pictures below are the recommended level switch circuit for
TXD, RXD, CTS, RTS. Each pin recommend two kinds of circuit, and you can select any one if necessarily.