HUAWEI ME909s Series LTE Mini PCIe Module
Hardware Guide
Description of the Application Interfaces
Issue 02 (2016-09-07)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
22
As the RESIN_N signal is relatively sensitive, it is recommended that you install a
10 nF to 0.1 µF capacitor near the RESIN_N pin of the interface for filtering. In
addition, when you design a circuit on the PCB of the interface board, it is
recommended that the circuit length should not exceed 20 mm and that the circuit
should be kept at a distance of 2.54 mm (100 mil) at least from the PCB edge.
Furthermore, you need to wrap the area adjacent to the signal wire with a ground
wire. Otherwise, the module may be reset due to interference.
The maximum Forward Voltage Drop of the diode used in the module is 0.6 V. So
when the host wants to reset the module, the low-level-voltage in the RESIN_N pin
should below 50 mV.
The ME909s Mini PCIe module supports hardware reset function. If the software of
the ME909s Mini PCIe module stops responding, you can reset the hardware through
the RESIN_N signal as shown in Figure 3-7 . When a low-level pulse is supplied
through the RESIN_N pin, the hardware will be reset. After the hardware is reset, the
software starts powering on the module and reports relevant information according to
the actual settings. For example, the AT command automatically reports ^SYSSTART.
Figure 3-7
Reset pulse timing
The RESIN_N pin is optional, which can be not connected.
3.4.5
LED_WWAN# Signal
ME909s Mini PCIe module provides an LED_WWAN# signal to indicate the work
status.
This function is disabled by default, it is controlled by AT^LEDCTRL. For details about
the command, please refer to
HUAWEI ME909s Series LTE Module AT Command
Interface Specification
.
Table 3-4
State of the LED_WWAN# pin
No. Operating Status
LED_WWAN#
1
No service or Restricted service Outputs: low (0.1s)-high (0.1s)-low
(0.1s)-high (1.7s)
2s cycle
2
Register to the network
Outputs: low (0.1s)-high (1.9s)
2s cycle
3
Dial-up successfully
Outputs: low