NEO-M8U - Hardware Integration Manual
UBX-15016700 - R07
Hardware description
Page 6 of 28
Production Information
☞
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.
☞
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
NEO-M8U Data Sheet
[1])
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 [1].
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
www.u-blox.com
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.
