To use this option I_Meas jumper and SJ2 shall be left open.
3.6.2 UART / USB
The TTL-232R-3V3 cable is used for USB/UART connection between PC and the evaluation
board. The IO level of the TTL-232R-3V3 cable is 3.3V. Using the FTDI-driver the PC will
show a virtual COM-Port which can be used to communicate with the module.
3.6.3 UART direct
If a micro-controller is to be connected to the module, use the
P3
connector. The UART of
the host can be directly connected to P3 (Pins are labelled on the evaluation board). The
module
RXD
line must be handled accordingly by your host (i.e. pulled up while inactive and
during module boot-up).
Beware of IO level compatibility. The host must obey the values stated in the module’s
manual. Especially the IO level restrictions must be implemented by a host system (i.e.
using a level shifter to use the allowed IO levels).
3.6.4 SPI direct
If a micro-controller is to be connected to the module, use the
P3
connector and
WAKE_UP/SPI_INT
(
P4
pin 3). The SPI of the host can be directly connected to these pins. For easy orientation
the pins are labelled on the evaluation board with its functions.
Beware of IO level compatibility. The host must obey the values stated in the module’s
manual. Especially the IO level restrictions must be implemented by a host system (i.e.
using a level shifter to use the allowed IO levels).
3.6.5 LFXO crystal
For higher LFCLK accuracy (better than ±250ppm) a low frequency crystal oscillator of
32.768kHz (LFXO) shall be used. A crystal, 3.2 ×1.6mm package, for example
can be placed on the evaluation board to position Q1. The needed load capacitance can be
reached with capacitors C9 and C10, 0402 package.
nRF52840 pin P0.00/XL1 and P0.01/XL12 are connected to module pad LED_1 and LED_2
respectively. If an LFXO is mounted to the EV board the solder bridge SJ1 and SJ3 shall
be disconnected using a cutter, therefore the LED1 and LED2 function is no longer available.
For standard firmware the external crystal is not needed. To enable use of the
LFXO a custom firmware is required.
Mini evaluation board user manual version 1.3
© June 2021
www.we-online.com/wireless-connectivity
21
