Virtual Com Port; 32 Khz Crystal Oscillator; Nfc Connector - Ublox BMD-34 EVK Series User Manual

2.5 Virtual COM port

The evaluation board allows for easy serial communication with the BMD-34 series modules
and a connected computer. The Interface IC provides a virtual COM port USB device that
connects to four GPIO pins on the module, allowing for UART communication with or without
hardware flow control. The UART lines can be completely removed from the circuit by breaking
the associated jumpers.
BMD-34 Pin Name
P0.05
P0.06
P0.07
P0.08
Table 2: Virtual COM port

2.6 32 kHz crystal oscillator

The evaluation board has a 32.768 kHz crystal oscillator connected to the BMD-34 module by
default. This allows the module to use any of the three available low frequency (LF) clock
sources: an internal calibrated RC oscillator, an internal synthesized clock (derived from the
32 MHz clock), or an external crystal oscillator. The external crystal oscillator is the most
accurate and lowest power LF clock option. For applications without strict time keeping
requirements, the internal calibrated RC oscillator is often suitable. The crystal is connected
to the module through a solder select jumper, allowing either the crystal or the IO header to be
connected to the module's GPIO pins.
Figure 7: Schematic – 32 kHz crystal

2.7 NFC connector

Connection to an external NFC antenna is provided through a Molex flat-flex connector, Part
number 051281-0594. Capacitors "C2" and "C3" provide tuning of the NFC antenna for
resonance at 15.56 MHz.
Figure 8: NFC connector
UBX-19033356 - R03
BMD-34 Function
RTS
TXD
CTS
RXD
Hardware description
BMD-34 EVK - User guide
Jumper Interface IC Function
J05 CTS
J06 RXD
J07 RTS
J08 TXD
Page 10 of 20