Integration Manual

ANNA-B4 series - System integration manual
UBX-21000517 - R03 Contents Page 18 of 76
C1-Public
Function
Description
Default ANNA-B4 pin
Configurable GPIOs
ADC input
8/10/12-bit analog to digital converter
Any analog
Analog comparator
input
Compare two voltages, capable of generating wake-
up events and interrupts
Any analog
PWM output
Output complex pulse width modulation waveforms
Any
Connection status
indication
Indicates if a Bluetooth LE connection is maintained
BLUE**
Any
* = If left unconfigured ** = If using u-connectXpress software. For pin number, see also the ANNA-B412 data sheet [6].
Table 11: GPIO custom functions configuration
2.8 NFC interface
Figure 5 shows some important aspects of the NFC antenna design, where:
• The NFC antenna coil must be connected differentially between the NFC1 and NFC2 pins of the
device.
• Two external capacitors should be used to tune the resonance of the antenna circuit to 13.56 MHz.
Figure 5: NFC antenna design
The value of the required tuning capacitors (C
tune
) is calculated with the two equations shown below.
An antenna inductance of L
ant
= 2 μH gives tuning capacitors in the range of 130 pF on each pin. For
good performance, match the total capacitance on NFC1 and NFC2.


󰆒


󰇛
  
󰇜





󰆒



 

 

 






󰇛
  
󰇜



 

 

⚠ As the pins for the NFC interface in ANNA-B402 series modules can be used as normal GPIOs, it is
important that all NFC pins are correctly configured in the software. Connecting an NFC antenna
to pins that are configured for GPIO might damage the module. In ANNA-B412 series modules, NFC
pins are always set to "NFC mode".