MeiG_SLM156_Hardware Design Manual
MeiG Smart Technology Co., Ltd
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In order to meet the requirements of USB data bus signal’s completeness, the impedance R1/R2/R3/R4
must be set near the module and the resistances should be set closely. The branching-off connecting
testing point should be as short as possible.
In order to guarantee the USB performance, the principles below should be followed in circuit design:
Module USB_VBUS is for detecting the plugging in and out of USB, not for supplying power for the
module;
In order to reduce the signal interference of USB high speed data transmission, connect R1 and R2
between USB_DM and USB_DP interface circuit to improve the data transmission rate. It is
recommended that you use R1 and R2
of 0Ω;
In order to improve the antistatic performance of USB interface, it is recommended to add ESD
protection components on USB_DP and USB_DM interface circuit. It is recommended that you use
ESD components with junction capacitance less than 1pF;
In order to ensure that the USB is reliable, consider more about the protection of USB when
designing, such as the protection of USB on Layout requires impedance control of 90Ω for
USB_DP, USB_DM, tracing strictly according to differential requirements, and keeping away from
the interference signal as far as possible;
Do not trace the USB line in the crystal oscillator, oscillator, magnetic device and RF signal; it is
recommended to trace inner differential line and up and down around the package.\
3.10.3 USB Driver
SLM156 supports various operation systems, such as PC operation systems: Windows 2000,
Windows XP, Windows 10,Windows Vista32/64, Windows 7/8, embedded operation system:
Windows CE5.0/6.0, Windows Mobile5.0/6.0, which requires private USB driver support;
For different operating systems and different VID and PID, USB driver provides different driver files.
Contact supporting staff if you have specific requirements;
SLM156 also supports embedded operating systems of Linux and Android. System brings its own
driver usbserial.ko as Linux kernel system. There is no specialized USB diver for SLM156,
usbserial.ko with loading system aims to realize USB loading SLM156. It is important to find the
driver file usbserial.ko and load PID and VID in system.
3.11 UART Interface
SLM156 provides two interfaces: main interface and debugging interface. Main features of these two
interfaces are shown as follows:
Main interface supports 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600bpsbaud
rate, the default baud rate is115200bps, which is used for data transmission and AT command.
Debugging interface supports 115200bps baud rate, which is used for Linux control and log print.
