NINA-B2 series - System integration manual
UBX-18011096 - R05
System description
Page 8 of 35
C1- Public
Pin
State during boot
Default
Behavior
Description
27
0
ESP boot mode (factory boot)
ESP Factory boot
Mode/RMII clock line.
1
Pull-up*
Normal Boot from internal Flash
32
0
Silent
Printout on UART0 TXD
during boot
1
Pull-up*
UART0 TXD Toggling
36
0
VDD_SDIO=3.3V
(Not allowed)
Internal flash voltage
1
10 k
Ω
pull-up
VDD_SDIO=1.8V
(VDD_SDIO should always be at 1.8 V)
*About 30 k
Ω
Table 2: NINA-B2 series boot strapping pins
1.7
Serial Interfaces
Universal asynchronous serial interface (UART)
The NINA-B2 series module provides a Universal Asynchronous Serial Interface (UART) for data
communication. The following UART signals are available:
•
Data lines (
RXD
as input,
TXD
as output)
•
Hardware flow control lines (
CTS
as input,
RTS
as output)
•
DSR
and
DTS
are used to set and indicate the system modes
The UART can be used as 4-wire UART with hardware flow control and 2-wire UART with only
TXD
and
RXD
. In 2-wire mode,
CTS
must be connected to the GND on the NINA-B2 module.
The UART interface is also be used for firmware upgrade. See also
The u-connectXpress software adds the
DSR
and
DTR
pins to the UART interface. These pins are not
used as they were originally intended but are used instead to control the state of NINA modules.
Depending on the configuration,
DSR
can be used to:
•
Enter command mode
•
Disconnect and/or toggle connectable status
•
Enable/disable the rest of the UART interface
•
Enter/wake up from the Stop mode
The functionality of the
DSR
and
DTR
pins are configured by AT commands. See also the
u-connectXpress AT commands manual [1] for more information.
See NINA-B2 series data sheet [2] for characteristic information about the UART interface.
Interface
Default configuration
UART interface
115200 baud, 8 data bits, no parity, 1 stop bit, hardware flow control
Table 3: Default settings for the UART port while using the u-blox connectivity software
It is advisable to make the UART available either as test points or connected to a header for firmware
upgrade.
The IO level of the UART will follow the
VCC_IO
.
Serial peripheral interface (SPI)
⚠
On NINA-B2, SPI is supported from software version 3.0.0 onwards.
In addition to UART support, NINA-B2 modules also include a Serial Peripheral Interface (SPI) for data
communication. The module acts as an SPI slave.
