Pressure Click

How does it work?

Pressure Click is based on the LPS331AP, a high accuracy, low-power 24-bit absolute barometric pressure sensor from STMicroelectronics. The LPS331AP provides a typical relative accuracy over pressure of ±0.1mbar and absolute accuracy of ±2mbar with high overpressure capability. It measures absolute pressure from 260mbar to 1260mbar over a wide operating temperature range. The complete device includes a sensing element based on a piezoresistive Wheatstone bridge and an interface that takes the information from the sensing element to the host MCU as a digital signal.

The sensing element consists of a suspended membrane realized inside a single mono-silicon substrate capable of detecting pressure, manufactured using a dedicated process developed by ST called VENSENS. This process allows the building of a mono-silicon membrane above an air cavity with a controlled gap and defined pressure. On the other hand, the LPS331AP’s interface is manufactured using a standard CMOS process and factory calibrated at three temperatures and two pressures for sensitivity and accuracy.

Pressure Click allows using both I2C and SPI interfaces. The selection can be made by positioning SMD jumpers labeled as COMM SEL in an appropriate position. Note that all the jumpers’ positions must be on the same side, or the Click board™ may become unresponsive. While the I2C interface is selected, the LPS331AP allows choosing the least significant bit (LSB) of its I2C slave address using the SMD jumper labeled I2C ADD. This Click board™ also possesses an additional interrupt pin, routed to the INT pin on the mikroBUS™ socket, indicating when a specific pressure event occurs.

This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing 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 Pressure 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	INT	Interrupt
SPI Chip Select	CS	3	CS	RX	14	NC
SPI Clock	SCK	4	SCK	TX	13	NC
SPI Data OUT	SDO	5	MISO	SCL	12	SCL	I2C Clock
SPI Data IN	SDI	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Pressure Click electrical specifications

Software Support

We provide a library for the Pressure 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 Pressure Click driver.

Key functions

• Generic Single Write function.

• Generic Multiple Read function.

• Pressure Get function.

Example Description

This is a example which demonstrates the use of Pressure Click board. Measured pressure and temperature data from the LPS331AP sensor on Pressure click.

 void application_task( void ) 
 { 
     uint8_t status; 
     float press; 
     float temp; 

     status = pressure_get_status( &pressure, PRESSURE_FLAG_MASK_P_DATA_RDY | 
                                              PRESSURE_FLAG_MASK_T_DATA_RDY ); 

     while (!status) 
     { 
         status = pressure_get_status( &pressure, PRESSURE_FLAG_MASK_P_DATA_RDY | 
                                                  PRESSURE_FLAG_MASK_T_DATA_RDY ); 
     } 

     press = pressure_get_pressure( &pressure ); 
     temp = pressure_get_temperature( &pressure ); 

     log_printf( &console, "** Pressure is %.2f mbarrn", press ); 
     log_printf( &console, "** Temperature is %.2f ", temp ); 
     log_write( &console, deg_cels, LOG_FORMAT_LINE ); 
     log_write( &console, "**************************************", 
                LOG_FORMAT_LINE ); 

     Delay_ms( 500 ); 
 }

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.Pressure

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. UART terminal is available in all MikroElektronika compilers.

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.