3.2 Module Configuration

Use the ASCII command interface for configuring the GPIO pins of the RNBD451 module to different functions. The following table provides the details about the various pins and functions in the RNBD451 module that are available for configuration and their default configuration settings.

Note: This configuration is not applicable in HCI mode.

Table 3-2. Configurable Functions and Descriptions
Pin	Function Name	Description
PB5	Bluetooth® status LED	To indicate the Bluetooth Low Energy connection status by a specific LED flash pattern, see the following pattern description: Standby mode – No Bluetooth Low Energy connection. The RNBD451 module is in Advertisement or Scan state. Flash one time for every three seconds. ON – 50 ms OFF – 2950 ms Linked mode – Bluetooth Low Energy ACL link is connected, regardless of whether it is in the Central or Peripheral role. Flash two times for every 1.5 seconds. ON – 50 ms OFF – 150 ms ON – 50 ms OFF – 1050 ms DFU mode – The RNBD451 module is in MCU DFU procedure. Flash 4 times for every two seconds. ON – 100 ms OFF – 100 ms Note: By default, the Bluetooth status LED is turned OFF. The user can enable this feature by using the `SR,<hex16>` command. For example `SR,0001`. For more details, refer to the RNBD451 Bluetooth Low Energy Module User’s Guide (DS50003467).
PB1	ADC	A dedicated ADC input pin where an analog signal can be the input to the RNBD451 module. The RNBD451 module performs the ADC conversion using a fixed reference and provides the digital value that can be read using a command. For more details, refer to the RNBD451 Bluetooth Low Energy Module User’s Guide (DS50003467).
PB8, PB10, PB11, PA0, PA1, PB12, PB13 and PA10	I/O level control	Host MCU can assert the RN command to set some GPIO pins as output pins to set their level or input pins to read their level.
PB2	UART mode switch	When the host MCU pulls the UART mode switch pin from low to high (rising edge), the RNBD451 module switches to the Data mode. When the host MCU pulls the UART mode switch pin from high to low (falling edge), the RNBD451 module switches to the Command mode. When the host MCU uses the RN command to switch the mode, the host MCU keeps the UART mode switch pin to the original setting. Note: By default, the UART mode switch functionality is not assigned on to the PB2 pin. The user can enable this feature using the `SR,<hex16>` command, for example, `SR,0002`. For more details, refer to the RNBD451 Bluetooth Low Energy Module User’s Guide (DS50003467).
PB4	UART RX indication	If the RNBD451 module’s low power is enabled, the host MCU must wake up the RNBD451 module before sending the UART data out. Pull the UART RX indication pin low to wake up the system).
PA3	RSSI indication	Use this indication pin to indicate the quality of the link based on the RSSI level. If the RSSI level is lower than the specified threshold value, the RSSI indication pin goes low.
PA2	UART TX indication	UART TX indication is an output pin. Provides indication if the RNBD451 module is transmitting to host MCU over UART. Pulled low before UART TX begins and pulled high after UART TX is over.

Table 3-3. Status Indication Pins
BT_Status_Ind1 (PB3)	BT_Status_Ind2 (PB7)	RNBD451 Status
Low	Low	Bluetooth® Low Energy is disconnected
Low	Low	Data transmission channel is closed
High	Low	Bluetooth Low Energy is connected
High	Low	Data transmission channel is closed
High	High	Bluetooth Low Energy is connected
High	High	Data transmission channel is opened
Low	High	DFU mode (local or Over-the-air Profile Client (OTAPC))
Note: By default the Bluetooth status indication feature is disabled in the firmware. The user can enable this feature via `SR,<hex16>` command, for example, `SR,1000`. For more details, refer to the RNBD451 Bluetooth Low Energy Module User’s Guide (DS50003467).