Learn the language of pressure with DPS422 and STM32F446RE

Pressure 9 Click is based on the DPS422, a digital barometric air pressure sensor from Infineon. It can be used to measure absolute pressure values from 300 to 1200hPa. The sensor contains a highly accurate capacity-based Micro Electro-Mechanical Sensor (MEMS), along with a high resolution 24-bit sigma-delta A/D converter (ADC). The MEMS also features a set of factory calibration parameters, stored into its OTP memory. They allow high-precision pressure and temperature data conversions to be performed, enabling results in physical units. By adjusting the oversampling ratio, the developer can find a perfect balance between the accuracy, speed (output data rate), and power consumption, in accordance to the application requirements. MEMS consists a set of tubular vacuum cells, covered by membranes. By applying a pressure, capacitance of the cell is changed proportionally. Several vacuum cells are connected in parallel, allowing for better sensitivity and less noise. The capacitance of the cells is measured and converted to a voltage which is sampled by the internal 24-bit ADC. The result is available over I2C or SPI interface, depending on the position of the COMM SEL jumpers. The conversion formula is then applied to the raw result value, providing

pressure and temperature values in human readable format. Pressure 9 click supports both SPI and I2C communication interfaces, allowing it to be used with a wide range of different MCUs. The communication interface can be chosen by moving SMD jumpers grouped under the COM SEL to an appropriate position (SPI or I2C). The slave I2C address can also be configured by a SMD jumper, when operated in the I2C mode: a SMD jumper labeled as ADD SEL is used to set the least significant bit (LSB) of the I2C address. When set to 0, the 7-bit I2C slave address becomes 0b1110110x. If set to 1, the address becomes 0b1110111x. The last digit (x) is the R/W bit. Please note that each jumper should be moved to the same position, else the communication with the host MCU may not be possible. One of distinctive features of the DPS422 is the FIFO buffer with 32 slots, allowing to buffer both pressure and temperature readings. The FIFO buffer can be used as a temporary storage for the incoming data, allowing for reduced data traffic through the communication bus. The FIFO buffer can be very useful for writing an optimized MCU firmware. The least significant bit (LSB) of the result stored within the FIFO buffer, determines if the stored

data represents pressure, or temperature (1 is used for pressure, 0 for temperature). A bit within the FIFO status register indicates if the buffer is full or if the watermark level has been reached. The FIFO buffer can also be disabled, allowing data to be fetched from the output registers, directly. Pressure and thermal data are available at the output, in 24-bit, two’s complement format. To convert the raw data into a human-readable format, the firmware of the host MCU has to obtain the calibration data. Calibration coefficients are then used within pressure or temperature conversion formulas. The required formulas can be found within the datasheet of the DPS422. However, this Click board™ comes with the mikroSDK compatible library of functions that simplify the firmware development. The developer is able to use simple function calls, which perform all the necessary data conversion, returning the pressure and thermal data in human readable format. This Click Board™ is designed to be operated by 3.3V logic levels only. A proper logic voltage level translation should be performed before the Click board™ is used MCUs which are operated at 5V.

Nucleo-64 with STM32F446RE MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin

headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is

provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.