Laird Connectivity Sentrius BT610 Sensor

Overview

The Sentrius™ BT610 Sensor is a battery powered, Bluetooth v5 Long Range integrated sensor platform that uses a Nordic Semiconductor nRF52840 ARM Cortex-M4F CPU.

The sensor has the following features:

ADC
CLOCK
FLASH
GPIO
I2C
MPU
NVIC
PWM
QSPI
RADIO (Bluetooth Low Energy and 802.15.4)
RTC
Segger RTT (RTT Console)
SPI
UART
WDT

More information about the board can be found at the Sentrius BT610 website [1].

Hardware

Supported Features

The BT610 Sensor supports the following hardware features:

Interface	Controller	Driver/Component
ADC	on-chip	adc
CLOCK	on-chip	clock_control
FLASH	on-chip	flash
GPIO	on-chip	gpio
I2C(M)	on-chip	i2c
MPU	on-chip	arch/arm
NVIC	on-chip	arch/arm
PWM	on-chip	pwm
QSPI	on-chip	qspi
RADIO	on-chip	Bluetooth, ieee802154
RTC	on-chip	system clock
RTT	Segger	console
SPI(M)	on-chip	spi
UART	on-chip	serial
WDT	on-chip	watchdog

Connections and IOs

LED

Two LEDs are visible through the BT610 housing lid. Note that the LEDs can be driven either directly, or via PWM. PWM should be used when current consumption is required to be minimised.

LED_1 (red) = LED0 = P1.07 (Red LED 1)
LED_2 (green) = LED1 = P1.03 (Green LED 2)
LED_PWM_1 (red) = LED0PWM = P1.07 (Red PWM LED 1)
LED_PWM_2 (green) = LED1PWM = P1.03 (Green PWM LED 2)

Push button

The BT610 incorporates three mechanical push buttons. Note these are only accessible with the housing cover removed.

Two of the buttons are available for use via the board DTS file, as follows.

BUTTON_1 = SW0 = P0.24 (Boot button SW1)
BUTTON_2 = SW1 = P1.01 (Tamper switch SW2)

A third mechanical push button is provided to allow reset of the on-board microcontroller.

Magnetoresistive sensor

The BT610 incorporates a Honeywell SM351LT magnetoresistive sensor. Refer to the Honeywell SM351LT datasheet [2] for further details.

MAG_1 = SW2 = P1.15 (SM3531LT_0)

External flash memory

A 64Mbit external flash memory part is available for storage of application images and data. Refer to the Macronix MX25R6435FZNIL0 datasheet [6] for further details.

The flash memory is connected to the on-board QSPI device controller.

MX25R64 = QSPI

Voltage reference

A precision 2.5V voltage reference is provided on the V_REF input for use during AD measurements.

This can deliver up to 50mA peak and 20mA continuous current.

Sensor connectivity

The BT610 incorporates three terminal blocks J5, J6 & J7 that allow connectivity to its sensor inputs, as follows.

Terminal Block J5

Pin No.	Name	Description	Direction
1	EXT_SPI_CS_2	External SPI CS 2	OUT
2	GND	GND	(N/A)
3	AIN4	Analog Input 4	IN
4	AIN3	Analog Input 3	IN
5	GND	GND	(N/A)
6	AIN2	Analog Input 2	IN
7	AIN1	Analog Input 1	IN
8	GND	GND	(N/A)
9	DIN2	Digital Input 2	IN
10	DO2	Digital Output 2	OUT

Terminal Block J6

Pin No.	Name	Description	Direction
1	DO1	Digital Output 1	OUT
2	DIN1	Digital Input 1	IN
3	GND	GND	(N/A)
4	THERM4	Thermistor Input 4	IN
5	THERM3	Thermistor Input 3	IN
6	GND	GND	(N/A)
7	THERM2	Thermistor Input 2	IN
8	THERM1	Thermistor Input 1	IN
9	GND	GND	(N/A)
10	B+ OUT	Ext. sensor power supply	(N/A)

Terminal Block J7

Pin No.	Name	Description	Direction
1	UART_1_RTS	UART 1 RTS	IN
2	UART_1_CTS	UART 1 CTS	OUT
3	UART_1_RXD	UART 1 RXD	IN
4	UART_1_TXD	UART 1 TXD	OUT
5	EXT_I2C_SCL	External I2C SCL	OUT
6	EXT_I2C_SDA	External I2C SDA	IN/OUT
7	EXT_SPI_CLK/TRACEDATA3	Ext. SPI CLK/TRACE DATA 3	OUT
8	EXT_SPI_MISO	External SPI MISO	IN
9	EXT_SPI_MOSI	External SPI MOSI	OUT
10	EXT_SPI_CS_1	External SPI CS 1	OUT

Analog inputs

The four external Analog Inputs are multiplexed to a single host microcontroller AD input, AIN_1, via a TI TMUX1204 multiplexer.

Refer to the TI TMUX1204 datasheet [4] for further details.

Signals up to 12V, to a maximum of 50mA, can be applied to the external Analog Inputs.

External Analog Input connections are made to the multiplexer as follows.

Input	MUX Input
AIN1	S1
AIN2	S2
AIN3	S3
AIN4	S4

A TI TCA9538 port expander is used to determine the mode of each Analog Input, for either voltage or current measurement, and also to control the mutliplexer. A high level applied to the appropriate expander port pin enables the associated analog input as a current input; when a low logic level is applied, voltage measurement mode is selected.

Refer to the TI TCA9538 datasheet [5] for further details.

The expander port connections are as follows.

Pin	Function
P0	AIN1 mode
P1	AIN2 mode
P2	AIN3 mode
P3	AIN4 mode
P4	MUX A0
P5	MUX A1
P6	(N/C)
P7	(N/C)

The following illustrates some possible configuration values for the port expander. Note that it is possible for combinations of voltage and current measurement to be applied such that some external Analog Inputs measure current and others voltage. This is not shown below.

Expander value	Selected Analog Input & mode
b’00000000’	AIN1, voltage measurement
b’00000001’	AIN1, current measurement
b’00010000’	AIN2, voltage measurement
b’00010010’	AIN2, current measurement
b’00100000’	AIN3, voltage measurement
b’00100100’	AIN3, current measurement
b’00110000’	AIN4, voltage measurement
b’00111000’	AIN4, current measurement

Circuitry associated with the analog input measurements can be disabled when not in use.

A GPIO is used to control this behaviour, as shown below.

ANALOG_ENABLE	Behaviour
0	Disabled
1	Enabled

Thermistor inputs

The four external thermistor inputs are connected to a single AD input, AIN_2, via a TI TMUX1204 multiplexer.

Refer to the TI TMUX1204 datasheet [4] for further details.

External analog input connections are made to the multiplexer as follows.

Input	MUX Input
THERM1	S1
THERM2	S2
THERM3	S3
THERM4	S4

The same port expander used to select external analog inputs is also used to select external thermistor inputs.

The table below defines possible values that can be written.

Expander value	Selected Analog Input
b’00000000’	THERM1
b’00010000’	THERM2
b’00100000’	THERM3
b’00110000’	THERM4

A GPIO line is used to enable electronics associated with thermistor measurement. This is controlled as shown below.

THERM_ENABLE	Behaviour
0	Enabled
1	Disabled

Note the thermistor circuit must be calibrated before use. A suggested method for achieving this is described in the BT610 Zephyr Application Thermistor Calibration [7] application note.

Digital inputs

Two external digital inputs are available for connection to external signals. For the digital level being applied to be detected, an appropriate output pin must first be set. This approach is taken to ensure supporting circuitry can be powered down when the input state is not being determined. When in use, the external digital input level can be read from the appropriate input pin.

The output and input pins required are as follows.

Enable Pin	Input Read Pin
DIN_1_ENABLE	DIN_1
DIN_2_ENABLE	DIN_2

Digital outputs

Two external digital outputs are available to provide signals to or to directly drive external equipment.

To provide a high level on the external digital output, a high logic level is applied to the appropriate host microcontroller output.

The output pins required are as follows.

Output Pin	External Sensor Terminal
DO_1_MCU	DO1
DO_2_MCU	DO2

External power supply

Power can be supplied to external sensors via the B+ OUT terminal. This is enabled by setting the BATTERY_OUTPUT_ENABLE GPIO line. In addition, the external supply can be boosted to 5V by setting the HIGH_SUPPLY_ENABLE GPIO line. When 5V is not selected, the external power supply follows the battery voltage.

Up to 50mA peak and 20mA continuous current can be delivered by the External Power Supply.

External sensor I2C port

External I2C sensors can be connected on the external I2C port. Note that external I2C sensors should be powered from the B+ terminal to ensure applied voltage levels match those expected internally by the board.

Required pins are as follows.

Output Pin	External Sensor Terminal
SCL_PIN	EXT_I2C_SCL
SDA_PIN	EXT_I2C_SDA

External sensor SPI port

Up to 2 external SPI sensors can be connected on the external SPI port. Note that external SPI sensors should be powered from the B+ terminal to ensure applied voltage levels match those expected internally by the board.

Required pins are as follows.

Output Pin	External Sensor Terminal
SCK_PIN	EXT_I2C_SCL
MOSI_PIN	EXT_I2C_SDA
MISO_PIN	EXT_SPI_MISO
SDA_PIN	EXT_I2C_SDA
CS_GPIOS	EXT_I2C_SDA
CS_GPIOS	EXT_I2C_SDA

Programming and Debugging

Applications for the bt610 board configuration can be built and flashed in the usual way (see Building an Application and Run an Application for more details); however, the standard debugging targets are not currently available.

The BT610 features a 10 way header, J3, for connection of a programmer/debugger, with pinout as follows.

Pin No.	Name	Description
1	3.3V	Power Supply, 3.3V
2	SWDIO	Data Input/Output
3	GND	GND
4	SWDCLK	Clock Pin
5	GND	GND
6	SWO	Trace Output Pin
7	(N/C)	Not Connected
8	(N/C)	Not Connected
9	GND	GND
10	nRESET	Reset Pin

Access to the sensor debug UART is facilitated by a 6 pin header, J1, with pinout as follows.

Pin No.	Name	Description	Direction
1	GND	GND	N/A
2	UART_0_RTS	UART 0 RTS Pin	IN
3	3.3V	Power Supply, 3.3V	N/A
4	UART_0_RX	UART 0 RX Pin	IN
5	UART_0_TX	UART 0 TX Pin	OUT
6	UART_0_CTS	UART 0 CTS Pin	OUT

Note that pin 3 requires a solder bridge to be closed to enable powering of the BT610 board via the UART connector.

Flashing

Follow the instructions in the Nordic nRF5x Segger J-Link page to install and configure all the necessary software. Further information can be found in Flashing. Then build and flash applications as usual (see Building an Application and Run an Application for more details).

Here is an example for the Hello World application.

First, run your favorite terminal program to listen for output.

NOTE: On the BT610, the UART lines are at TTL levels and must be passed through an appropriate line driver circuit for translation to RS232 levels. Refer to the MAX3232 datasheet [3] for a suitable driver IC.

$ minicom -D <tty_device> -b 115200

Replace <tty_device> with the port where the BT610 can be found. For example, under Linux, /dev/ttyUSB0.

Then build and flash the application in the usual way.

# From the root of the zephyr repository
west build -b bt610 samples/hello_world
west flash

Note that an external debugger is required to perform application flashing.

Debugging

The bt610 board does not have an on-board J-Link debug IC as some nRF5x development boards, however, instructions from the Nordic nRF5x Segger J-Link page also apply to this board, with the additional step of connecting an external debugger.

Testing Bluetooth on the BT610

Many of the Bluetooth examples will work on the BT610. Try them out:

Testing the LEDs and buttons on the BT610

There are 2 samples that allow you to test that the buttons (switches) and LEDs on the board are working properly with Zephyr:

You can build and flash the examples to make sure Zephyr is running correctly on your board. The button, LED and sensor device definitions can be found in boards/arm/bt610/bt610.dts.