VT-MOD-CELL-B48 Hardware User Manual
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5.4 USB Signals
VT-MOD-CELL-B48 is compliant with USB 2.0 high speed specification.
VT-MOD-CELL-B48 uses USB drive. On the PC one ports can be mapped out,
respectively:
a. 1 ACM port, carrying AT commands, is mainly used for data traffic;
b. 1 CDC-ECM standard card, mainly for service information, the RNDIS interface
can be customized.
5.5 Status Indication Signals
There are four GPIO pins of VT-MOD-CELL-B48module. The mode LED functions
as the network mode indicator and the status LED function as the signal strength
indicator. The LEDs are controlled by a sink current source. The high voltage is the
voltage of VCC3V3 (with the typical value of 3.3V). According to LED feature, you
can adjust the LED brightness by adjusting the impedance of resistor R.
Figure 4-3 Recommended circuits of the LED pins