Vdd_Usb: Usb Interface Power Supply; Vcc_Rf: Output Voltage Rf; Interfaces; Uart - u-blox NEO-M8U Hardware Integration Manual

☞
Avoid high resistance on the V_BCKP line: During the switch from main supply to backup supply,
a short current adjustment peak can cause high voltage drop on the pin with possible
malfunctions.
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If no backup supply voltage is available, connect the V_BCKP pin to VCC.
☞
As long as power is supplied to the NEO-M8U module through the VCC pin, the backup battery is
disconnected from the RTC and the BBR to avoid unnecessary battery drain (see Figure 1). In this
case, VCC supplies power to the RTC and BBR.
Figure 1: Backup battery and voltage (for exact pin orientation, see the

1.3.3 VDD_USB: USB interface power supply

VDD_USB supplies the USB interface. If the USB interface is not used, the VDD_USB pin must be
connected to GND. For more information about correctly handling the VDD_USB pin, see section 1.4

1.3.4 VCC_RF: Output voltage RF

The VCC_RF pin can supply an active antenna or external LNA. For more information, see section 0

1.4 Interfaces

1.4.1 UART

NEO-M8U 3D dead reckoning module includes a Universal Asynchronous Receiver Transmitter
(UART) serial interface RXD/TXD supporting configurable baud rates. The baud rates supported are
specified in the NEO-M8U Data Sheet
The signal output and input levels are 0 V to VCC. An interface based on RS232 standard levels (+/-
12 V) can be implemented using level shifters such as Maxim MAX3232. Hardware handshake signals
and synchronous operation are not supported.

1.4.2 USB

A USB version 2.0 FS (Full Speed, 12 Mb/s) compatible interface is available for communication as an
alternative to the UART. The USB_DP integrates a pull-up resistor to signal a full-speed device to the
host. The VDD_USB pin supplies the USB interface.
u-blox provides Microsoft® certified USB drivers for Windows Vista, Windows 7, Windows 8 and
Windows 10. These drivers are available at our website at
USB external components
The USB interface requires some external components to implement the physical characteristics
required by the USB 2.0 specification. These external components are shown in Figure 2 and listed in
Table 1. To comply with USB specifications, VBUS must be connected through an LDO (U1) to pin
VDD_USB on the module.
UBX-15016700 - R07
Production Information
NEO-M8U - Hardware Integration Manual
NEO-M8U Data Sheet
[1].
www.u-blox.com
Hardware description
[1])
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