Data Sheet

LC840PA
Datasheet
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– Interactive / development mode (nAutoRUN pin held at VDD).
Make provision to allow operation in the required mode. Add jumper to allow nAutoRUN pin to be held high or low
(LC840PA has internal 13K pull-down by default) OR driven by host GPIO.
▪ I2C
It is essential to remember that pull-up resistors on both I2C_SCL and I2C_SDA lines are not provided in the LC840PA
module and MUST be provided external to the module as per I2C standard if I2C is utilized..
▪ SPI
Implement SPI chip select using any unused SIO pin within your smartBASIC application script or Nordic application then
SPI_CS is controlled from the software application allowing multi-dropping.
▪ SIO pin direction
LC840PA modules shipped from production with smartBASIC FW, all SIO pins (with default function of DIO) are mostly
digital inputs (see Pin Definitions Table2). Remember to change the direction SIO pin (in your smartBASIC application
script) if that particular pin is wired to a device that expects to be driven by the LC840PA SIO pin configured as an output.
Also, these SIO pins have the internal pull-up or pull-down resistor-enabled by default in firmware (see Pin Definitions
Table 2). This was done to avoid floating inputs, which can cause current consumption in low power modes (e.g.
StandbyDoze) to drift with time. You can disable the PULL-UP or Pull-down through their smartBASIC application.
Note: Internal pull-up, pull down will take current from VDD.
▪ SIO_02 pin and OTA smartBASIC application download feature
SIO_02 is an input, set with internal pull-down (in FW). Refer to latest firmware release documentation on how SIO_02 is
used for Over the Air smartBASIC application download feature. The SIO_02 pin must be pulled high externally to enable
the feature. Decide if this feature is required in production. When SIO_02 is high, ensure nAutoRun is NOT high at same
time; otherwise you cannot load the smartBASIC application script.
• NFC antenna connector
To make use of the Laird flexi-PCB NFC antenna, fit connector:
– Description – FFC/FPC Connector, Right Angle, SMD/90d, Dual Contact,1.2 mm Mated Height
– Manufacturer – Molex
– Manufacturers Part number – 512810594
Add tuning capacitors of 300 pF on NFC1 pin to GND and 300 pF on NFC2 pins to GND if the PCB track length is similar
as development board.
▪ nRESET pin (active low)
Hardware reset. Wire out to push button or drive by host.
By default module is out of reset when power applied to VCC pins.
▪ External 32.768kHz crystal
A crystal that meets specification should be used. The capacitance value of added load capacitors should be tuned to
meet all specifications for frequency and oscillation margin.
▪ SIO_38 special function pin
This is for future use by Laird. It is currently a Do Not Connect pin if using the smartBASIC FW.
▪ LC840PA pin2 and pin4 are Do No Connect pins (on BL654 SIO_34 and SIO_36)
Customer MUST NOT connect anything to LC840PA pin2 and pin4 which are Do No connect pins.
▪ LC840PA pin16 (WAKE) (active low)
Wake module from sleep in IEEE 802.15.4 ProFLEX application. Signal is active LOW (internal pull-up) and requires a
minimum 20uS pulse to awaken a sleeping module.
▪ LC840PA pins 18, 20, 21 and 22 (LED1 – LED4)
In IEEE 802.15.4 ProFLEX application, LEDs provide status for heartbeat (module operating), RF packet Tx and RF packet
Rx events. This pins may be connected to LEDs, connected to Host for status information, or remain unconnected.