NEO-M8P - Hardware Integration Manual
UBX-15028081 - R05
Early Production Information
Hardware description
Page 6 of 27
Figure 1: Backup battery and voltage (for exact pin orientation, see the
NEO-M8P Data Sheet
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
Communication interfaces
The following interfaces are used for command and control using the UBX proprietary binary protocol and for
reception and transmission of a RTCM message stream when operating in RTK mode.
1.4.1
UART
NEO-M8P positioning modules include a Universal Asynchronous Receiver Transmitter (UART) serial interface
RXD/TXD
supporting configurable baud rates. The baud rates supported are specified in the
u-blox 8 /
u-blox M8
Receiver Description including Protocol Specification
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 a 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 operating systems (Vista, Windows 7, 8 and 10).
These drivers are available for download from our website: www.u-blox.com
1.4.2.1
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 a signal indicating that the device is present
and ready to communicate. This should be avoided by disabling the LDO (U1) using the enable signal (EN) of the
VCC-LDO or the output of a voltage supervisor. Depending on the characteristics of the LDO (U1) it is
recommended to add a pull-down resistor (R11) at its output to ensure
VDD_USB
is not floating if the LDO (U1)
is disabled or the USB cable is not connected i.e. VBUS is not supplied.
USB bus-powered mode is not supported.
