Data Sheet

LC840PA

Datasheet

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Pin Definition Notes:

Note 8

The smartBASIC firmware has SIO pins as Digital (Default Function) INPUT pins, which are set PULL-UP by

default. This avoids floating inputs (which can cause current consumption to drive with time in low power modes

(such as Standby Doze). You can disable the PULL-UP through your smartBASIC application.

All of the SIO pins (with a default function of DIO) are inputs (apart from SIO_05 and SIO_06, which are outputs):

▪ SIO_06 (alternative function UART_TX) is an output, set High (in the firmware).

▪ SIO_05 (alternative function UART_RTS) is an output, set Low (in the firmware) (optional use by ProFLEX).

▪ SIO_08 (alternative function UART_RX) is an input, set with internal pull-up (in the firmware).

▪ SIO_07 (alternative function UART_CTS) is an input, set with internal pull-down (in the firmware) (unused

by ProFLEX).

▪ SIO_02 is an input set with internal pull-down (in the firmware). It is used for OTA downloading of

smartBASIC applications. Refer to the latest firmware extension documentation for details.

▪ UART_RX, UART_TX, and UART_CTS are 3.3 V level logic (if VDD is 3.3 V; such as SIO pin I/O levels

track VDD). For example, when Rx and Tx are idle, they sit at 3.3 V (if VDD is 3.3 V). Conversely,

handshaking pins CTS and RTS at 0V are treated as assertions.

▪ SIO_20 (alternative function UART2_RX) is an input, set with internal pull-up (in the firmware)

▪ SIO_21 (alternative function UART2_TX) is an output, set High (in the firmware).

Note 9

LC840PA also allows an option to connect an external higher accuracy (±20 ppm) 32.768 kHz crystal to the

LC840PA pins SIO_01/XL2 (pin 41) and SIO_00/XL1 (pin 42). This provides higher accuracy protocol timing and

helps with radio power consumption in the system standby doze/deep sleep modes by reducing the time that the

Rx window must be open.

External 32.768kHz crystal not required for LC840PA module normal operation with Bluetooth LE/smartBASIC

firmware. The on-chip 32.768 kHz LFRC oscillator provides the standard accuracy of ±500 ppm, with calibration

required every eight seconds (default) to stay within ±500 ppm.

External 32.768kHz crystal is required for IEEE802.15.4:2006 ProFLEX firmware.

Note 10

LC840PA power supply options:

▪ Option 1 – Normal voltage power supply mode entered when the external supply voltage is connected to

both the VDD and VDD_HV pins (so that VDD equals VDD_HV). Connect external supply within range 3.0V

to 3.6V range to LC840PA VDD and VDD_HV pins.

▪ Option 2 – High voltage mode power supply mode (using LC840PA VDD_HV pin) entered when the

external supply voltage in ONLY connected to the VDDH pin and the VDD pin is not connected to any

external voltage supply. Connect external supply within range 3.0V to 5.5V range to LC840PA VDD_HV pin.

LC840PA VDD pin left unconnected.

For either option, if you use USB interface then the LC840PA VBUS pin must be connected to external supply

within the range 4.35V to 5.5V. When using the LC840PA VBUS pin, you MUST externally fit a 4.7uF to ground.