Uart Interface; Uart Design Guide - SimCom SIM7020C Hardware Design

3.5

UART Interface

SIM7020 provides a 7-wire UART1 (universal asynchronous serial transmission) interface as DCE
(Data Communication Equipment). AT commands and data transmission can be performed through
UART1 interface.UART2 can be used for debugging and download software.
3.5.1

UART Design Guide

The following figures show the reference design.
MODULE ( DCE)
Serial port
UART _ DTR
UART _ DCD
The SIM7020 UART is 1.8V voltage interface. If user's UART application circuit is 3.3V voltage
interface, the level shifter circuits should be used for voltage matching. The TXB0108RGYR
provided by Texas Instruments is recommended. The following figure shows the voltage matching
reference design.
SIM7020_Hardware_Design_V1.02
TXD
RXD
RTS
CTS
UART1_RI
Figure 10: UART full modem
MODULE ( DCE)
TXD
RXD
RTS
UART CTS
DTR
DCD
Wake up host
RI
Figure 11: UART null modem
CUSTOMER (DTE)
Serial port
TXD
RXD
RTS
CTS
DTR
DCD
RING
HOST ( DTE)
TXD
RXD
RTS
CTS
DTR
DCD
RING
Interrupt
21
Smart Machine Smart Decision
UART
2018-07-25