NINA-W1 series - System integration manual
UBX-17005730 - R11 System description Page 10 of 55
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
pull-up VDD_SDIO=1.8V
(VDD_SDIO should always be at 1.8 V)
Table 1: NINA-B2 series boot strapping pins
☞ On NINA-W13/W15 modules, pin 27 must be in default state during the boot.
☞ Care must be taken if an RMII interface is to be included in the application design. As pin 27
connect to the RMII, it is important that the pin is in the correct state during the module boot and
before the RMII interface turns on. For further connection information, see section 1.7.2.1.
☞ On NINA-W10 modules, pin 27 is used to enter the ESP bootloader. Consequently, this pin must
be exposed on a pin header (or similar) to flash the module.
☞ During boot, pin 32 controls if additional system information should be transmitted on the UART
interface during startup. After the system has booted it is reconfigured to SPI_CS, the SPI chip
select signal.
☞ During boot, pin 36 controls the voltage level of the internal flash during startup. After the system
has booted it is reconfigured to SPI_MISO, the SPI slave data output signal. It must NOT be pulled
down by an external MCU or circuitry.
For the timing and algorithm for the detection of the SPI and RMII interfaces, also see the “Data and
command interfaces” section in the NINA-W13 and NINA-W15 data sheets [2], [4].
1.7 Data interfaces
1.7.1 Universal asynchronous serial interface (UART)
For data communication and firmware upgrade purposes, NINA-W1 series modules support an
interface comprised of three UARTs. Each UART supports the following signals:
• Data lines (RXD as input, TXD as output)
• Hardware flow control lines (CTS as input, RTS as output)
• DSR and DTS set and indicate the system modes
You can use the UARTs in 4-wire mode with hardware flow control, or in 2-wire mode with TXD and
RXD only. In 2-wire mode, CTS must be connected to the GND on the NINA-W1 module.
The UART interface is also be used for firmware upgrade. See the Software section for more
information.
The u-connectXpress software adds the DSR and DTR pins to the UART interface. Although these
pins are not used as they were originally intended, these 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 sleep or stop mode
The functionality of the DSR and DTR pins are configured by AT commands. For further information
about these commands, see the u-blox short range modules AT commands manual [1].
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