MeiG_SLM320_Hardware Design Manual
MeiG Smart Technology Co., Ltd
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In USB interface circuit design, to ensure USB performance, the following principles are recommended
in circuit design:
The module USB_VBUS is not used to power the module, but to detect USB insertion and
unplugging
；
In order to reduce the USB high speed data transmission of signal interference, in USB_DM
USB_DP interface circuit and concatenated R1 and R2 can improve the accuracy of data
transmission, 0
Ω
R1 and R2 are recommended
；
In order to improve the antistatic performance of USB interface, ESD protective devices are
recommended to be added to USB_DP and USB_DM interface circuits, and ESD devices with
junction capacitance less than 2pF are recommended. USB ESD protection device should be
placed as close as possible to USB interface
；
In order to ensure the USB work reliable, the design still need more consideration to the protection
of USB, such as the Layout of the protection of the USB, need to do to USB_DP and USB_DM 90
Ω
impedance control, strictly in accordance with the requirements of the differential line, as far as
possible away from the interference signal
；
Do not use USB cable under crystal oscillator, oscillator, magnetic device and RF signal. It is
recommended to use inner differential wiring and wrap the ground left, right, up and down.
3.9 Serial Port
SLM320 module has three serial ports: main serial port UART1, DEBUG serial port UART and download,
and RADIO frequency calibration serial port UART2. The main features of the main and debug serial
ports are described below.
The main serial port supports 4800Bps, 9600bps, 19200Bps, 38400Bps, 57600bps, 115200Bps,
230400bps baud rate. The default baud rate is 115200bps for data transmission and AT command
transmission.
Debugging serial port support 115200BPS baud rate, for r & D debugging use.
Table 10 Main serial port pin description
Pin Name
I/O
Pin
Description
UART1_RING
DO
62
Module output ring prompt
UART2_TXD
DO
63
Module sends data
CTS
I
64
Module clear send
RTS
O
65
The module requests to send
MAIN_TXD
O
67
Module sends data
MAIN_RXD
I
68
The module receives data
