30 min

Create smart and responsive environments with TSL2591 and STM32F756ZG that adapt to changing ambient conditions

The light whisperer: Crafting perfect ambiance with ease!

Ambient 21 Click with UNI Clicker

Published Sep 19, 2023

Click board™

Ambient 21 Click

Development board

UNI Clicker


NECTO Studio



Integrate ambient light sensing into home automation systems for enhanced security by adjusting outdoor lighting based on environmental conditions



Hardware Overview

How does it work?

Ambient 21 Click is based on the TSL2591, a high-sensitivity light-to-digital converter from ams AG. The TSL2591 provides ambient light sensing (ALS) that approximates the human eye response to light intensity under various lighting conditions and through different attenuation materials. It has a flexible and wide operating range of up to 88klx with the highest sensitivity of 188μlx, even when mounted behind dark glass. This sensor comes in a UV-rejection package, enabling its operation in IR light environments, making this board most suitable for various brightness control functions, helping to reduce power consumption. The TSL2591 contains two integrating analog-to-digital converters (ADC) that integrate currents from two photodiodes: one broadband photodiode (visible plus infrared) and one infrared-response

photodiode. These ADCs convert the photodiode currents into a digital output representing the irradiance measured on each channel. Ambient 21 Click communicates with an MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting Standard Mode operation with a clock frequency of 100kHz and Fast Mode up to 400kHz. Integration of both channels co-occurs. The conversion result is transferred to the appropriate channel data registers upon completion of the conversion cycle. The transfers are double-buffered to ensure that the integrity of the data is maintained. After the transfer, the device automatically begins the next integration cycle. This sensor also supports an interrupt feature, routed to the INT pin on the mikroBUS™ socket, that simplifies and improves

system efficiency by eliminating the need to poll a sensor for a light intensity value. The purpose of the interrupt function is to detect a meaningful change in light intensity, where the user can define the concept of a significant change in light intensity and time or persistence. Users can define a threshold above and below the current light level, where an interrupt is generated when the conversion value exceeds either of these limits. 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. Also, it comes equipped with a library containing functions and an example code that can be used as a reference for further development.

Ambient 21 Click top side image
Ambient 21 Click bottom side image

Features overview

Development board

UNI Clicker is a compact development board designed as a complete solution that brings the flexibility of add-on Click boards™ to your favorite microcontroller, making it a perfect starter kit for implementing your ideas. It supports a wide range of microcontrollers, such as different ARM, PIC32, dsPIC, PIC, and AVR from various vendors like Microchip, ST, NXP, and TI (regardless of their number of pins), four mikroBUS™ sockets for Click board™ connectivity, a USB connector, LED indicators, buttons, a debugger/programmer connector, and two 26-pin headers for interfacing with external electronics. Thanks to innovative manufacturing technology, it allows you to build

gadgets with unique functionalities and features quickly. Each part of the UNI Clicker development kit contains the components necessary for the most efficient operation of the same board. In addition to the possibility of choosing the UNI Clicker programming method, using a third-party programmer or CODEGRIP/mikroProg connected to onboard JTAG/SWD header, the UNI Clicker board also includes a clean and regulated power supply module for the development kit. It provides two ways of board-powering; through the USB Type-C (USB-C) connector, where onboard voltage regulators provide the appropriate voltage levels to each component on the board, or using a Li-Po/Li

Ion battery via an onboard battery connector. All communication methods that mikroBUS™ itself supports are on this board (plus USB HOST/DEVICE), including the well-established mikroBUS™ socket, a standardized socket for the MCU card (SiBRAIN standard), and several user-configurable buttons and LED indicators. UNI Clicker is an integral part of the Mikroe ecosystem, allowing you to create a new application in minutes. Natively supported by Mikroe software tools, it covers many aspects of prototyping thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

UNI clicker double image

Microcontroller Overview

MCU Card / MCU



8th Generation


ARM Cortex-M7

MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Power Supply
I2C Clock
I2C Data

Take a closer look


Ambient 21 Click Schematic schematic

Step by step

Project assembly

UNI Clicker front image hardware assembly

Start by selecting your development board and Click board™. Begin with the UNI Clicker as your development board.

UNI Clicker front image hardware assembly
Thermo 28 Click front image hardware assembly
SiBRAIN for STM32F745VG front image hardware assembly
Prog-cut hardware assembly
UNI Clicker MB 1 - upright/with-background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

After loading the code example, pressing the "DEBUG" button builds and programs it on the selected setup.

Application Output Step 1

After programming is completed, a header with buttons for various actions available in the IDE appears. By clicking the green "PLAY "button, we start reading the results achieved with Click board™.

Application Output Step 3

Upon completion of programming, the Application Output tab is automatically opened, where the achieved result can be read. In case of an inability to perform the Debug function, check if a proper connection between the MCU used by the setup and the CODEGRIP programmer has been established. A detailed explanation of the CODEGRIP-board connection can be found in the CODEGRIP User Manual. Please find it in the RESOURCES section.

Application Output Step 4

Software Support

Library Description

This library contains API for Ambient 21 Click driver.

Key functions:

  • ambient21_get_int_pin - This function returns the INT pin logic state

  • ambient21_read_raw_data - This function checks if the data is ready and then reads the raw ADC data from two channels

  • ambient21_measure_light_level - This function reads the raw ADC data from two channels and then measures the light level in lux based on those readings.

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

 * @file main.c
 * @brief Ambient 21 Click example
 * # Description
 * This example demonstrates the use of Ambient 21 click board by measuring 
 * the ambient light level in Lux.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver and performs the click default configuration.
 * ## Application Task
 * Waits for the data ready interrupt, then reads the ambient light level in Lux
 * and displays the results on the USB UART. By default, the data ready interrupt triggers 
 * upon every ADC cycle which occurs every 200ms.
 * @author Stefan Filipovic

#include "board.h"
#include "log.h"
#include "ambient21.h"

static ambient21_t ambient21;
static log_t logger;

void application_init ( void ) 
    log_cfg_t log_cfg;  /**< Logger config object. */
    ambient21_cfg_t ambient21_cfg;  /**< Click config object. */

     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, " Application Init " );

    // Click initialization.
    ambient21_cfg_setup( &ambient21_cfg );
    AMBIENT21_MAP_MIKROBUS( ambient21_cfg, MIKROBUS_1 );
    if ( I2C_MASTER_ERROR == ambient21_init( &ambient21, &ambient21_cfg ) ) 
        log_error( &logger, " Communication init." );
        for ( ; ; );
    if ( AMBIENT21_ERROR == ambient21_default_cfg ( &ambient21 ) )
        log_error( &logger, " Default configuration." );
        for ( ; ; );
    log_info( &logger, " Application Task " );

void application_task ( void ) 
    uint16_t lux;
    if ( !ambient21_get_int_pin ( &ambient21 ) )
        if ( AMBIENT21_OK == ambient21_measure_light_level ( &ambient21, &lux ) )
            log_printf ( &logger, " Ambient light level [Lux]: %u\r\n\n", lux );

void main ( void ) 
    application_init( );

    for ( ; ; ) 
        application_task( );

// ------------------------------------------------------------------------ END

Additional Support