Ultra-Low Press Click

How does it work?

Ultra-Low Press Click as its foundation uses the SM8436, a high precision, factory-calibrated pressure sensor for ultra-low pressure measurements ranging from -20 to 500Pa from TE Connectivity. It combines a low-pressure MEMS die with a 16 bit ASIC, utilizing DSP for multi-dimensional polynomial error correction. The calibrated pressure output data, alongside status information on the sensor integrity and unique serial number, is available via the digital data interface.

This Click board™ represents an ideal solution for lower pressure-sensing capabilities in industrial and medical markets. From HVAC and gas flow to continuous positive airway pressure (CPAP), ventilation, and patient monitoring applications, the ability to detect small pressure changes is critical. This demand requires pressure sensor to be highly accurate and provide long-term stability, which is achieved with this board.

Ultra-Low Press Click communicates with MCU using the standard I2C 2-Wire interface with a maximum clock frequency of up to 400kHz. It is fully adjustable through software registers where the digital output data is available with a word length of 16-bit. The I2C interface allows setting the SM8436 into a Sleep Mode using a specific command (Enter Sleep Mode), which confirms low consumption of typically less than 10μA. In Sleep Mode, no pressure data is acquired. To wake up the sensor from its Sleep state, the clock line SCL shall be toggled (a rising edge at SCL will wake up the device).

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to use the I2C communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

Specifications

Pinout diagram

This table shows how the pinout on Ultra-Low Press Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	NC
	NC	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Ultra-Low Press Click electrical specifications

Software Support

We provide a library for the Ultra-LowPress Click as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on Mikroe github account.

Library Description

This library contains API for Ultra-LowPress Click driver.

Key functions:

• ultralowpress_cfg_setup – Config Object Initialization function.
• ultralowpress_init – Initialization function.

Examples description

This application reads the serial number of the sensor. If there were no errors it continues reading temperature and pressure data from the sensor.

void application_task ( void ) 
{
    if ( ultralowpress_ready_to_read( &ultralowpress ) )
    {
        ultralowpress_clear_status( &ultralowpress );
        float temp = ultralowpress_get_temp( &ultralowpress );
        float press = ultralowpress_get_press( &ultralowpress );
        log_printf( &logger, " > Temperature[ C ]: %.2frn > Pressure[ Pa ]: %.2frn", temp, press );
    }
    Delay_ms( 100 );
}

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager(recommended way), downloaded from our LibStock™ or found on Mikroe github account.

Other Mikroe Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.UltraLowPress

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.