Monitor and respond to variations in light intensity using BH1620FVC and PIC18F27J13

Capturing lightscapes: The artistry of ambient sensor tech

Published Dec 29, 2023

Click board™

Ambient 12 Click

Dev Board

EasyPIC v7

Compiler

NECTO Studio

MCU

PIC18F27J13

Unveil the potential of our ambient light intensity sensing in autonomous systems, where it plays a crucial role in object recognition and environmental perception

Hardware Overview

How does it work?

Ambient 12 Click is based on the BH1620FVC, an analog current-output ambient light sensor from Rohm Semiconductor. The BH1620FVC comprises photodiodes, amplifiers, and current mirror circuits, where the output current, in proportion to brightness, is converted to the voltage value by an external resistor. It is characterized by spectral sensitivity close to human eyes sensitivity with low sensitivity variations of +/-15%. It also has four configurable modes of operation: shutdown mode associated with three gain modes: high-gain

mode with an illuminance detection range of 1000lx, medium-gain mode up to 10.000lx, and low-gain mode up to 100.000lx. The desired gain mode is selected through CS and PWM pins of the mikroBUS™ socket labeled GC1 and GC2. The output voltage of the BH1620FVC can be converted to a digital value using MCP3221, a successive approximation A/D converter with a 12-bit resolution from Microchip, using a 2-wire I2C compatible interface, or can be sent directly to an analog pin of the mikroBUS™ socket labeled as

AN. Selection can be performed by onboard SMD jumper labeled as A/D SEL to an appropriate position marked as AN and ADC. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VIO 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.

Features overview

Development board

EasyPIC v7 is the seventh generation of PIC development boards specially designed to develop embedded applications rapidly. It supports a wide range of 8-bit PIC microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB-B. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyPIC v7 allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of

the EasyPIC v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use various external power sources, including an external 12V power supply, 7-23V AC or 9-32V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B) connector. Communication options such as

USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from PIC10F, PIC12F, PIC16F, PIC16Enh, PIC18F, PIC18FJ, and PIC18FK families. EasyPIC v7 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

Microcontroller Overview

MCU Card / MCU

Architecture

PIC

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

3800

Used MCU Pins

mikroBUS™ mapper

Analog Signal

RA3

RST

Gain Control Signal 1

RA5

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

Gain Control Signal 2

RC1

PWM

INT

I2C Clock

RC3

SCL

I2C Data

RC4

SDA

Power Supply

Ground

GND

Take a closer look

Schematic

Step by step

Project assembly

EasyPIC v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v7 as your development board.

NECTO Output Selection Step Image hardware assembly

In the advanced settings, pay special attention to the Redirect standard output field. By default, it is set to Application output as the method of displaying final results. To show results via a UART terminal, select the “UART” option in that field and click the “SAVE” button. You will be returned to the Compiler field, and now you can move on to the next step by pressing the “NEXT” button.

Rotary B 2 Click front image hardware assembly

EasyPIC v7 MB 2 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

EasyPIC PRO v7a Display Selection Necto Step hardware assembly

Track your results in real time

Application Output

After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.

Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.

In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".

The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

Software Support

Library Description

This library contains API for Ambient 12 Click driver.

Key functions:

ambient12_read_adc_voltage - This function reads raw 12-bit ADC data and converts it to voltage by using I2C serial interface
ambient12_voltage_to_lux - This function calculates illuminance (lux) based on the voltage input
ambient12_set_gain_mode - This function sets the gain mode.

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 12 Click Example.
 *
 * # Description
 * This example demonstrates the use of Ambient 12 click board.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and sets the gain mode to M-Gain which can detect the illuminance of up to 10000 lux.
 *
 * ## Application Task
 * Reads the ADC voltage and then calculates the illuminance from it.
 * The calculated value of illuminance in lux is being displayed on the USB UART approximately once per second. 
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "ambient12.h"

static ambient12_t ambient12;       /**< Ambient 12 Click driver object. */
static log_t logger;                /**< Logger object. */

void application_init ( void )
{
    log_cfg_t log_cfg;              /**< Logger config object. */
    ambient12_cfg_t ambient12_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 );
    Delay_ms( 100 );
    log_info( &logger, " Application Init " );

    // Click initialization.
    ambient12_cfg_setup( &ambient12_cfg );
    AMBIENT12_MAP_MIKROBUS( ambient12_cfg, MIKROBUS_1 );
    if ( ADC_ERROR == ambient12_init( &ambient12, &ambient12_cfg ) )
    {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );
    }

    ambient12_set_gain_mode ( &ambient12, AMBIENT12_MODE_M_GAIN );
    log_printf( &logger, " M-Gain mode selected.\r\n Up to 10000 lux can be measured.\r\n" );
    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    float voltage = 0;
    
    if ( AMBIENT12_OK == ambient12_read_adc_voltage ( &ambient12, &voltage ) )
    {
        log_printf( &logger, " Illuminance : %ld Lux\r\n\n", ambient12_voltage_to_lux( &ambient12, voltage ) );
    }
    
    Delay_ms( 1000 );
}

void main ( void ) 
{
    application_init( );

    for ( ; ; ) 
    {
        application_task( );
    }
}

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