NavSpark PX1175RDP Getting Started page 6

Interface of RTK/DR EVB (2/3)
NAME
USB_1 USB port for NMEA out, RTK correction & binary command in, 115200
USB_2
USB port for updating firmware to R-chip,
and C/D must be open, 115200
RTK_STAT_B Status signal
Low : RTK Fix for Heading
Blink : RTK Float for Heading
High : otherwise
RTK_STAT_R Reserved
RESET_N Reset signal from external device, active low
TXD_B Data output from B-chip's UART1
RXD_B Data input to B-chip's UART1. Use only when USB_1 is not used, or there
will be drive contention.
SAFEBOOT_N Leave unconnected for normal use. Pull-low for loading firmware into
empty or corrupted flash memory from ROM mode
DESCRIPTION
jumper A/B must be shorted