Beginner
10 min

Provide a pulse train or a square wave proportional to ambient light intensity with TSL230BR and ATmega328

Programmable light-to-frequency converter

LightHz Click with Arduino UNO Rev3

Published Mar 09, 2024

Click board™

LightHz Click

Dev Board

Arduino UNO Rev3

Compiler

NECTO Studio

MCU

ATmega328

Achieve an accurate, high-resolution light intensity measurement in various applications, from basic ambient light sensing to rough color detection

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Hardware Overview

How does it work?

LightHz Click is based on the TSL230BR, a programmable light-to-frequency converter from ams OSRAM. It combines a configurable silicon photodiode and a current-to-frequency converter and has a high-resolution conversion of light intensity with no external components. The sensor responds over the 320nm to 1050nm light range and is temperature-compensated for the ultraviolet-to-visible light range of 320nm to 700nm. Device sensitivity is selectable in three ranges, providing two decades of adjustment, while the full-scale output frequency can be scaled by one of four preset values with 5% absolute tolerance. The LightHz Click uses its frequency output to communicate with the host MCU over the OUT pin of the mikroBUS™ socket. The board comes with four SMD jumpers labeled MCU ON-BRD, which allows you to choose the scaling and sensitivity configuration to be controlled by the host MCU

rather than the onboard jumper selection. The latter is set by default. Using default MCU ON-BRD selection, the sensitivity is controlled by two logic inputs on S0 and S1 on the jumper labeled SENSITIVITY SELECTION. You can choose between 1x, 10, 100x, and power-down options by combining four available positions. The sensitivity of this sensor is adjusted using an electronic iris technique, similar to an aperture control. This way, it is possible to change the device's response to a given amount of light, which allows the device to be optimized to a given light level while preserving the output frequency range. The 100x option is set by default. Using default MCU ON-BRD selection, the output frequency scaling is controlled by two logic inputs on S2 and S3 on the jumper labeled FREQUENCY SCALING. By a combination of four available positions, you can choose between 1, 2, 10, and 100 dividing values. The value 1 means no

division as a direct output and is a fixed-pulse-width pulse train. The higher divider means lower frequency ranges for high-resolution measurement; the 100 value is set by default. If your choice is to control the sensor by the host MCU by selecting the MCU ON-BRD jumpers to MCU, then the logic inputs for scaling and selection become available on the S0, S1, S2, and S3 pins of the mikroBUS™ socket. The combination tables are in our documentation section below. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the PWR SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. However, the 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.

LightHz Click hardware overview image

Features overview

Development board

Arduino UNO is a versatile microcontroller board built around the ATmega328P chip. It offers extensive connectivity options for various projects, featuring 14 digital input/output pins, six of which are PWM-capable, along with six analog inputs. Its core components include a 16MHz ceramic resonator, a USB connection, a power jack, an

ICSP header, and a reset button, providing everything necessary to power and program the board. The Uno is ready to go, whether connected to a computer via USB or powered by an AC-to-DC adapter or battery. As the first USB Arduino board, it serves as the benchmark for the Arduino platform, with "Uno" symbolizing its status as the

first in a series. This name choice, meaning "one" in Italian, commemorates the launch of Arduino Software (IDE) 1.0. Initially introduced alongside version 1.0 of the Arduino Software (IDE), the Uno has since become the foundational model for subsequent Arduino releases, embodying the platform's evolution.

Arduino UNO Rev3 double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

AVR

MCU Memory (KB)

32

Silicon Vendor

Microchip

Pin count

32

RAM (Bytes)

2048

You complete me!

Accessories

Click Shield for Arduino UNO has two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the Arduino UNO board without effort. The Arduino Uno, a microcontroller board based on the ATmega328P, provides an affordable and flexible way for users to try out new concepts and build prototypes with the ATmega328P microcontroller from various combinations of performance, power consumption, and features. The Arduino Uno has 14 digital input/output pins (of which six can be used as PWM outputs), six analog inputs, a 16 MHz ceramic resonator (CSTCE16M0V53-R0), a USB connection, a power jack, an ICSP header, and reset button. Most of the ATmega328P microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the Arduino UNO board with our Click Shield for Arduino UNO, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.

Click Shield for Arduino UNO accessories 1 image

Used MCU Pins

mikroBUS™ mapper

S1 Logic Input
PC0
AN
S3 Logic Input
PD2
RST
S2 Logic Input
PB2
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
S0 Logic Input
PD6
PWM
Frequency Output
PC3
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

LightHz Click Schematic schematic

Step by step

Project assembly

Click Shield for Arduino UNO front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Arduino UNO Rev3 as your development board.

Click Shield for Arduino UNO front image hardware assembly
Arduino UNO Rev3 front image hardware assembly
Barometer 13 Click front image hardware assembly
Prog-cut hardware assembly
Arduino UNO Rev3 MB 1 - upright/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
Arduino UNO MCU Step 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 LightHz Click driver.

Key functions:

  • lighthz_set_sensitivity - This function sets the sensor sensitivity

  • lighthz_set_frequency_scaling - This function sets the sensor frequency scaling

  • lighthz_get_freq_pin - This function returns the freq pin logic state

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 LightHz Click Example.
 *
 * # Description
 * This example demonstrates the use of LightHz click board by measuring and displaying
 * the frequency of clock output signal. The higher the light intensity the higher the frequency.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and sets the sensitivity mode and frequency scaling in case
 * the onboard jumpers are set to MCU instead to ON-BRD.
 *
 * ## Application Task
 * Measures the clock output frequency using the polling method and delays. The results are being
 * sent to the USB UART.
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "lighthz.h"

static lighthz_t lighthz;   /**< LightHz Click driver object. */
static log_t logger;        /**< Logger object. */

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    lighthz_cfg_t lighthz_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.
    lighthz_cfg_setup( &lighthz_cfg );
    LIGHTHZ_MAP_MIKROBUS( lighthz_cfg, MIKROBUS_1 );
    if ( DIGITAL_OUT_UNSUPPORTED_PIN == lighthz_init( &lighthz, &lighthz_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    lighthz_set_sensitivity ( &lighthz, LIGHTHZ_SENS_100X );
    lighthz_set_frequency_scaling ( &lighthz, LIGHTHZ_FSCALE_100 );
    
    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    uint32_t freq_cnt = 0;
    uint16_t sample_cnt = 0;

    // Wait for the clock rising edge signal
    while ( !hal_ll_gpio_read_pin_input( &lighthz.freq.pin ) );

    // A loop for measuring the clock frequency counts. It's not an ideal implementation.
    // Here we should use an external interrupt on the clock pin rising edge and a timer interrupt
    // for the best accuracy, however, those interrupt features have not yet been implemented in the SDK. 
    while ( ( sample_cnt < LIGHTHZ_SAMPLE_COUNTS ) && ( freq_cnt < LIGHTHZ_MAX_COUNTS_PER_S ) )
    {
        // A single iteration in the loops below should take as close to 10us as possible
        // So to improve the measurement accuracy adjust the delay below for your system
        while ( hal_ll_gpio_read_pin_input( &lighthz.freq.pin ) )
        {
            freq_cnt++;
            Delay_us ( LIGHTHZ_DELAY_US );
        }
        while ( !hal_ll_gpio_read_pin_input( &lighthz.freq.pin ) )
        {
            freq_cnt++;
            Delay_us ( LIGHTHZ_DELAY_US );
        }
        sample_cnt++;
    }
    freq_cnt /= sample_cnt;

    // The higher the light intensity the higher the frequency.
    log_printf( &logger, " Frequency: %.1f Hz\r\n\n", ( float ) LIGHTHZ_MAX_COUNTS_PER_S / freq_cnt );

    Delay_ms ( 1000 );
}

int main ( void ) 
{
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}

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

Additional Support

Resources