Vdd_Usb: Usb Interface Power Supply; Vcc_Rf: Output Voltage Rf; Interfaces; Uart - u-blox NEO-8Q Series Hardware Integration Manual

NEO-8Q / NEO-M8 - Hardware Integration Manual
Figure 1: Backup battery and voltage (for exact pin orientation, see the corresponding product data sheet in Related
documents)
Real-Time Clock (RTC)
The RTC is driven by a 32 kHz oscillator using an RTC crystal. If the main supply voltage fails, and a battery is
connected to V_BCKP, parts of the receiver switch off, but the RTC still runs providing a timing reference for the
receiver. This operating mode is called Hardware Backup Mode, which enables all relevant data to be saved in
the backup RAM to allow a hot or warm start later

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 2.4.

1.4 Interfaces

1.4.1 UART

The NEO-8Q and NEO-M8 series modules include a Universal Asynchronous Receiver Transmitter (UART) serial
interface RXD/TXD supporting configurable baud rates. The baud rates supported are specified in the
corresponding product data sheet in Related documents.
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.
Designs must allow access to the UART pin for future service and reconfiguration.

1.4.2 USB

A USB version 2.0 FS (Full Speed, 12 Mbit/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
operating systems. 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.
In USB self-powered mode, the power supply (VCC) can be turned off and the digital block is not powered. In
this case, since VBUS is still available, the USB host would still receive the signal indicating that the device is
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