Pressure 4 Click Board™

Product Code: MIKROE-3020

The Pressure 4 Click Board™ is an absolute barometric pressure measurement Click board™, which features a low power consumption, high precision barometric pressure sensor. Capable of using both SPI and I2C communication protocols, the Pressure 4 Click Board™ allows being interfaced with a broad range of various microcontroller units (MCUs). The sensor used on this Click board™ features onboard processing capabilities, such as the IIR filtering, used to filter out abrupt changes of pressure. Low power consumption allows the Pressure 4 Click Board™ to be used in many portable, battery-powered applications. Besides the pressure, it can also measure the ambient temperature, which can be used for the compensation calculations. Besides the pressure readings, the Pressure 4 Click Board™ also offers very accurate temperature reading, which is required for the pressure readings compensation. Oversampling up to 16 times combined with the filtering options allows very low noise influence on measurement results.

Depending on the application in which the Click board™ is used, different power saving, oversampling, and filtering settings can be implemented, resulting in an optimal performance in given conditions. All these features make the Pressure 4 Click Board™ an ideal solution for weather stations, indoor flying toys navigation, drones, variometers, and similar applications that rely on reliable barometric pressure measurements. How Does The Pressure 4 Click Board™ Work? The sensor used on the Pressure 4 Click Board™ is the BMP280, a digital pressure sensor, from Bosch Sensortech. This sensor is produced using the Bosch proprietary APSM manufacturing technology. APSM is an abbreviation for the Advanced Porous Silicon Membrane, which is CMOS compatible technology, used to hermetically seal the sensor cavity, in an all-silicon process. This advanced MEMS technology offers a high measurement precision of only 0.12 hPa, as well as low TOC (thermal coefficient) of only 1.5 Pa/K. The sensor is enclosed in a small metal lid housing and is very resilient: it can operate in a range of 300 hPa to 1100 hPa but can withstand up to 20,000 hPa before the membrane breaks down. The BMP280 offers a set of pressure and temperature measurement options. It can be programmed to skip either thermal or pressure measurement, allowing faster measurement of the required property. The low TOC of only 1.5K/Pa allows reading of the pressure with very small drift over temperature. Resolution of 0.12 hPa allows calculating of the altitude with the accuracy of 1m, which is ideal for indoor navigation applications (drones, flying toy models, and similar). Since this device is aimed at low power applications, it is powered by the mikroBUS™ 3.3V rail and does not allow voltages up to 5V. Therefore the Pressure 4 Click Board™ supports only 3.3V MCUs and it is not intended to be connected or controlled via the 5V MCU without a proper level shifting circuitry. This sensor is comprised of a mixed signal front end (ASIC) and the piezo-sensitive pressure sensing element. The ASIC section provides analog to digital conversion of the measurement as well as the signal processing, in the form of the IIR filtering. The measurement readings and the compensation parameters are available at I2C or SPI bus pins of the BMP280 routed to the mikroBUS™ standard SPI and I2C pins. Pressure 4 click offers a selection between the two, by switching SMD jumpers labeled as I2C SPI to an appropriate position. Note that all the jumpers have to be placed to the same side, as mixed SPI and I2C positions will render the Click board™ unresponsive. Additionally, selection of the I2C communication protocol allows the least significant bit (LSB) of the I2C slave address of the device to be set. This can be done with the SMD jumper, labeled as I2C ADDR. The overall power consumption depends on several factors, such as the oversampling value, measurement rate, power mode, standby duration, and so on. Bosch Sensortech recommends a set of operational parameters for different applications, in a form of a table, in the BMP280 datasheet. In general, this sensor allows several power modes, regardless of the selected measurement parameters: Sleep mode : keeps only the logic section of the sensor IC powered. It is possible to read the device ID and compensation parameters. The power consumption is minimal in this mode. Forced mode : when the Forced mode command is received, the device is awakened from the sleep mode; a single measurement is performed, according to previously programmed conversion parameters. After that, the device reverts to the Sleep mode, waiting to be triggered once more by repeated selection of the Force mode. The conversion results can be read from the registers since the Sleep mode keeps the logic section powered up. Normal mode : in this mode, conversions are cyclically repeated, with programmable standby periods after each measurement. The power co