Specifications

https://www.lairdconnect.com/wireless-
modules/bluetooth-modules/bluetooth-5-
modules/bl654-series-bluetooth-module-nfc
39
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▪ nAutoRUN pin and operating mode selection
nAutoRUN pin needs to be externally held high or low to select between the two BL654 operating modes at power-up:
– Self-contained Run mode (nAutoRUN pin held at 0V).
– 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
(BL654 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 BL654
module and MUST be provided external to the module as per I2C standard.
▪ 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
BL654 modules shipped from production with smart BASIC 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 BL654 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 Connectivity 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.
▪ Optional External 32.768kHz crystal
If the optional external 32.768kHz crystal is needed then use a crystal that meets specification and add load capacitors
whose values should be tuned to meet all specification for frequency and oscillation margin.
▪ SIO_38 special function pin
This is for future use by Laird Connectivity. It is currently a Do Not Connect pin if using the smartBASIC FW.
Checklist (for PCB):
▪ MUST locate BL654 module close to the edge of PCB (mandatory for the 451-00001 for on-board PCB trace antenna to
radiate properly).
▪ Use solid GND plane on inner layer (for best EMC and RF performance).
▪ All module GND pins MUST be connected to host PCB GND.
▪ Place GND vias close to module GND pads as possible.