Neo_M680 GPRS Module Hardware User Guide
Copyright © Neoway Technology Co., Ltd
22
SIM card is sensitive to GSM TDD noise and RF interference. So, the PCB design should meet the
following requirements:
The antenna should be installed far away from the SIM card and SIM card traces, especially to the
build-in antenna.
The SIM traces on the PCB should be as short as possible and shielded with GND copper.
The ESD diodes or small capacitors should be closed to SIM card on the PCB.
3.6
Running LED Indicator
Table 3-6
LED indicator
Signal
I/O
Function
Remarks
LIGHT
DO
Indicates running status
2.8 V output, max. 4 mA
High level drives the LED indicator
The LIGHT pin can output a 4 mA current and 2.8 V voltage, therefore the LED can be directly connected
to this pin with a resistor in series. For better luminance, drive the LED with a transistor instead.
Figure 3-20
LED indicator
When the module is running, the LED indicator is driven by the LIGHT to indicate different module status
with its various blink behaviors. You can set the blink mode by AT commands. For more details, see
Neo_M680 GPRS Module AT Command Set
.
LIGHT
GPRS
Module
1K
LIGHT
GPRS Module
10K
VCC
470
4.7K
