Data Sheet
NINA-B41-data sheet
2.5.2.2Secondary UART interface
The secondary UART interface can be used to "daisy chain" UART connections. It is useful in resource
constrained systems where the host controller only has one UART interface available. To use it, the
NINA-B3 module is configured to become a UART bridge, and UART data sent over the primary UART
interface flows into the secondary UART interface.
The secondary UART interface pins can be freely configured to any free NINA GPIO pins. It uses four
signals; RXD, TXD, CTS and RTS.
2.5.3u-blox Serial Port Service (SPS)
The serial port service feature enables serial port emulation over Bluetooth LE.
2.5.4System status signals
The RED, GREEN, and BLUE pins are used to signal the system status as shown in Table 4. They are
active low and are intended to be routed to an RGB LED.
Mode Status RGB LED color RED GREEN BLUE
Data mode/Extended Data mode (EDM) IDLE Green HIGH LOW HIGH
Command mode IDLE Orange LOW LOW HIGH
EDM/Data mode, Command mode CONNECTING Purple LOW HIGH LOW
EDM/Data mode, Command mode CONNECTED** Blue HIGH HIGH LOW
Table 4: System status indication
* = LED flashes on data activity
Note CONNECTING and CONNECTED reflect the u-blox SPS connection status.
2.5.5System control signals
The following input signals are used to control the system:
• RESET_N is used to reset the system. See section Module reset for detailed information.
• If SWITCH_2 is driven low during start up, the UART serial settings are restored to their default
values.
• The SWITCH_2 can be used to open a Bluetooth LE connection with a peripheral device.
• If both SWITCH_1 and SWITCH_2 are driven low during startup, the system will enter
bootloader mode.
• If both SWITCH_1 and SWITCH_2 are driven low during start up and held low for 10 seconds,
the system will exit the bootloader mode and restore all settings to their factory default.
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