Data Sheet

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LC840PA

Datasheet

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Pin Name

Default Function

Alternate

Function

In/

Out

Pull

Up/

Down

nRF52840

QFN Pin

nRF52840

QFN Name

Comment

GND

Added GND in the

LC840PA

GND

Added GND in the

LC840PA

GND

Added GND in the

LC840PA

GND

Added GND in the

LC840PA

Pin Definition Notes:

Note 1

SIO = Signal Input or Output. Secondary function is selectable in smartBASIC application or via Nordic SDK. I/O

voltage level tracks VDD. AIN = Analog Input.

Note 2

At reset, all SIO lines are configured as the defaults shown above.

SIO lines can be configured through the smartBASIC application script to be either inputs or outputs with pull-ups

or pull-downs. When an alternative SIO function is selected (such as I2C or SPI), the firmware does not allow the

setup of internal pull-up/pull-down. Therefore, when I2C interface is selected, pull-up resistors on I2C SDA and

I2C SCL must be connected externally as per I2C standard.

Note 3

JTAG (two-wire SWD interface), pin 1 (SWDIO) and pin 3 (SWDCLK).

JTAG is required because Nordic SDK and ProFLEX applications can only be loaded using JTAG (smartBASIC

firmware can be loaded using the JTAG as well as UART). We recommend that you use JTAG (2-wire interface)

to handle future LC840PA module smartBASIC firmware upgrades. You must wire out the JTAG (2-wire

interface) on your host design (see Figure 7, where four lines – SWDIO, SWDCLK, GND and VDD – should be

wired out. smartBASIC firmware upgrades can still be performed over the UART interface, but this is slower (60

seconds using UART vs. 10 seconds when using JTAG) than using the LC840PA JTAG (2-wire interface).

Upgrading smartBASIC firmware or loading the smartBASIC applications is done using the UART interface.

Note 4

Pull the nRESET pin (pin 19) low for minimum 100 milliseconds to reset the LC840PA.

Note 5

The SIO_02 pin (pin 50) must be pulled high externally to enable VSP (Virtual Serial Port) which would allow OTA

(over-the-air) smartBASIC application download. Refer to the latest firmware release documentation for details.

Note 6

Ensure that SIO_02 (pin 50) and AutoRUN (pin 5) are not both high (externally), in that state, the UART is

bridged to Virtual Serial Port service (this comment is for BL654PA smartBASIC). The LC840PA module does

not respond to AT commands and cannot load smartBASIC application scripts.

Note 7

Pin 5 (nAutoRUN) is an input, with active low logic. In the development kit it is connected so that the state is

driven by the host’s DTR output line. The nAutoRUN pin must be externally held high or low to select between the

following two LC840PA operating modes:

▪ Self-contained Run mode (nAutoRUN pin held at 0V –this is the default (internal pull-down enabled))

▪ Interactive/Development mode (nAutoRUN pin held at VDD)

The smartBASIC firmware checks for the status of nAutoRUN during power-up or reset. If it is low and if there is a

smartBASIC application script named $autorun$, then the smartBASIC firmware executes the application script

automatically, hence the name Self-contained Run Mode.