Create ambiance like never before and transform spaces with ease using BH1721FVC and STM32F410RB

Ambient 4 Click is based on the BH1721FVC, a 16-bit digital light sensor with the I2C serial interface from Rohm Semiconductor. This sensor has many features that make it a perfect solution for small designs such as the Ambient 4 Click board™. One of these features is certainly its high level of integration, that allows a minimal number of external components, leaving room for an additional I2C level translator IC, labeled as PCA9306, a reliable I2C level translator from Texas Instruments, proven in many designs. This allows a high number of microcontrollers (MCUs) to be interfaced with Ambient 4 click. The BH1721FVC sensor is also immune to flickering and its accuracy is not influenced by the light source type. It is calibrated so its spectral response is closely matched to a spectral response of the human eye. The BH1721FVC sensor of Ambient 4 click can operate in two modes: it can be operated in Low-Resolution mode and High-Resolution mode. While operating in the Low-Resolution mode, the measuring resolution is 8 lx per step. When operated in a High-Resolution mode, the accuracy is 1 lx per step. When sensing very low amounts of light, it is mandatory to use High-Resolution mode, since it is not possible to obtain valid results in Low-Resolution mode. The resolution can

be also fine-tuned by changing the measurement time. This is used to increase the sensitivity of the sensor, as well as to reduce the influence of the optical window if one is mounted over the sensor. Increasing of the measurement time allows light amount down to 0.25 lx to be detected. The Low-Resolution mode, in general, allows much shorter measurement times, while high resolution will use longer to place the conversion data on the 16-bit output register. As mentioned already, the spectral response of the sensor is closely matched to the response of the human eye. This means that the sensor outputs highest results for the light spectrum range between 500nm and 650 nm, which includes most of the light energy in the visible light spectrum: this is a color range from cyan to orange. The datasheet of the BH1721FVC offers a more accurate representation of the spectrum response, as well as for other operating parameters. The sensitivity of the sensor is also affected by the incidence angle of the light rays. The BH1721FVC datasheet offers an accurate representation of the sensor's field of view (FOV), but a light source with the incidence angle of ±45˚ will result with the measured ratio of 0.8 times compared to the same light source intensity perpendicular to the surface of the sensor. Since

the sensor output result is 16-bit, it is stored in the LSB/MSB format, in two separate output registers. To obtain a measurement data in proper units (Lux, lx), a data conversion has to be performed by the firmware of the host MCU. The datasheet of the BH1721FVC contains these conversion formulas, although Ambient 4 click comes supported by a library that contains the functions that simplify the use of the Click board™. The 16-bit light intensity data is present at the I2C interface output. The I2C bus lines are routed to the aforementioned PCA9306 level translator. This allows interfacing with the wide range of different MCUs, both 3.3V, and 5V. It is worth mentioning that the sensor requires a reset after the power-up sequence, in order to set its internal registers to their defaults. This can be achieved by pulling the DVI line of the sensor to a LOW logic level for at least 1 µs. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this 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.

Nucleo-64 with STM32F410RB 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.