Intermediate
30 min

Achieve precise spectral identification and color matching with AS7341 and PIC18F87K22

Shades of brilliance: Unmasking the spectral story

Spectrometer Click with EasyPIC PRO v8

Published Sep 24, 2023

Click board™

Spectrometer Click

Development board

EasyPIC PRO v8

Compiler

NECTO Studio

MCU

PIC18F87K22

Unleash the power of spectral analysis for accurate color matching, ensuring consistent and flawless results in design, manufacturing, and quality control

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Hardware Overview

How does it work?

Spectrometer Click is based on the AS7341, 11-channel spectral sensor frontend from ams OSRAM. This IC features six independent optical channels with a dedicated 16-bit light-to-frequency converter. The gain and integration time of the six channels can be adjusted with the serial interface. Wait time can be programmed to automatically set a delay between two consecutive spectral measurements and reduce overall power consumption. A multiplexer (SMUX) can access the other available channels, connecting them to one of the internal ADCs. It also features a 4x4-photodiode array. On top and below the photodiode array are two photodiodes with dedicated functions such as flicker detection and near-infrared response. This Click board includes an LDO AP7331 to provide the 1.8 V supply voltage for the AS7341 and 3 N-Channel MOSFET BSS138 for voltage level translation. The AS7341,

interrupt-driven IC, is controlled and monitored by registers accessed through the I²C serial interface. These registers provide device control functions and can be read to determine device status and data acquisition. The device supports 7-bit chip addressing and standard and full-speed clock frequency modes. It possesses eight optical channels distributed over the visible spectral range, clear and NIR channels to accurately measure and match colors, and a configurable sleep mode. The device also integrates a dedicated channel to detect 50Hz or 60Hz ambient light flicker. The flicker detection engine can also buffer data for calculating other flicker frequencies externally. Upon power-up, the Spectrometer Click initializes. During initialization (typically 200μs), the device will deterministically send NAK on I²C and cannot accept I²C transactions. All communication with the device must be delayed, and all outputs

from the device must be ignored, including interrupts. After initialization, the device enters the SLEEP state (the internal oscillator and other circuitry are inactive, resulting in ultra-low power consumption). Once the Power ON bit is enabled, the device enters the IDLE state where the internal oscillator and attendant circuitry are active, but power consumption remains low. Whenever the spectral measurement is enabled, the device enters the ACTIVE state. If the spectral measurement is disabled, the device returns to the IDLE state. 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.

Spectrometer Click top side image
Spectrometer Click bottom side image

Features overview

Development board

EasyPIC PRO v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, EasyPIC PRO v8 provides a fluid and immersive working experience, allowing access anywhere and under

any circumstances at any time. Each part of the EasyPIC PRO v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector.

Communication options such as USB-UART, USB DEVICE, and Ethernet are also included, including the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options (graphical and character-based LCD). EasyPIC PRO v8 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.

EasyPIC PRO v8 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Type

8th Generation

Architecture

PIC

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

80

RAM (Bytes)

3862

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Interrupt
RB0
INT
NC
NC
TX
NC
NC
RX
I2C Clock
RC3
SCL
I2C Data
RC4
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

Spectrometer Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC PRO v8 as your development board.

Fusion for PIC v8 front image hardware assembly
Buck 22 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
v8 SiBRAIN 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 Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image 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.

UART Application Output Step 1

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.

UART Application Output Step 2

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".

UART Application Output Step 3

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.

UART Application Output Step 4

Software Support

Library Description

This library contains API for Spectrometer Click driver.

Key functions:

  • spectrometer_raw_rd_val_mode_1 - This function is used to read out channels with SMUX configration 1; F1-F4, Clear

  • spectrometer_raw_rd_val_mode_2 - This function is used to read out channels with SMUX configration 2; F5-F8, Clear

  • spectrometer_flicker_detection - This function is used to detect flicker for 100 and 120 Hz.

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 
 * \brief Spectrometer Click example
 * 
 * # Description
 * This Click is an 11-channel spectrometer for spectral identification and color matching. The 
 * spectral response is defined in the wavelengths from approximately 350nm to 1000nm. 8 optical 
 * channels cover the visible spectrum, one channel can be used to measure near infra-red light
 * and one channel is a photo diode without filter (“clear”). The device also integrates a 
 * dedicated channel to detect 50Hz or 60Hz ambient light flicker. 
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initalizes I2C driver, performs safety check and makes an initial log.
 * 
 * ## Application Task  
 * This example shows the capabilities of the Spectrometer click
 * by reading out channels with SMUX configrations 1 and 2, detecting 
 * flicker for 100 and 120 Hz and displaying data via USART terminal.
 * 
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "spectrometer.h"

// ------------------------------------------------------------------ VARIABLES

static spectrometer_t spectrometer;
static log_t logger;

static uint8_t id_val;
static uint16_t ch_0;
static uint16_t ch_1;
static uint16_t ch_2;
static uint16_t ch_3;
static uint16_t ch_4;
static uint8_t f_val;
static uint8_t adc_buf[ 13 ];

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
{
    log_cfg_t log_cfg;
    spectrometer_cfg_t cfg;

    /** 
     * 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.

    spectrometer_cfg_setup( &cfg );
    SPECTROMETER_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    spectrometer_init( &spectrometer, &cfg );
    Delay_ms( 100 );
    
    spectrometer_generic_read ( &spectrometer, SPECTROMETER_ID, &id_val, 1 );
    if ( id_val == SPECTROMETER_ID_VALUE )
    {
        log_printf( &logger, "-------------------------\r\n" );
        log_printf( &logger, "   Spectrometer  click   \r\n" );
        log_printf( &logger, "-------------------------\r\n" );
    }
    else
    {
        log_printf( &logger, "-------------------------\r\n" );
        log_printf( &logger, "     FATAL  ERROR!!!     \r\n" );
        log_printf( &logger, "-------------------------\r\n" );
        for ( ; ; );
    }
    Delay_ms( 100 );
    
    spectrometer_def_cfg( &spectrometer );
    Delay_ms( 100 );
}

void application_task ( void )
{
    spectrometer_raw_rd_val_mode_1( &spectrometer, &adc_buf[ 0 ] );
    
    ch_0 = adc_buf[ 1 ];
    ch_0 <<= 8;
    ch_0 |= adc_buf[ 0 ];
    log_printf( &logger, " ADC0/F1 : %u\r\n", ch_0 );

    ch_1 = adc_buf[ 3 ];
    ch_1 <<= 8;
    ch_1 |= adc_buf[ 2 ];
    log_printf( &logger, " ADC1/F2 : %u\r\n", ch_1 );

    ch_2 = adc_buf[ 5 ];
    ch_2 <<= 8;
    ch_2 |= adc_buf[ 4 ];
    log_printf( &logger, " ADC2/F3 : %u\r\n", ch_2 );

    ch_3 = adc_buf[ 7 ];
    ch_3 <<= 8;
    ch_3 |= adc_buf[ 6 ];
    log_printf( &logger, " ADC3/F4 : %u\r\n", ch_3 );

    ch_4 = adc_buf[ 9 ];
    ch_4 <<= 8;
    ch_4 |= adc_buf[ 8 ];
    log_printf( &logger, " ADC4/Clear : %u\r\n", ch_4 );

    spectrometer_raw_rd_val_mode_2( &spectrometer, &adc_buf[ 0 ] );
    
    ch_0 = adc_buf[ 1 ];
    ch_0 <<= 8;
    ch_0 |= adc_buf[ 0 ];
    log_printf( &logger, " ADC0/F5 : %u\r\n", ch_0 );

    ch_1 = adc_buf[ 3 ];
    ch_1 <<= 8;
    ch_1 |= adc_buf[ 2 ];
    log_printf( &logger, " ADC1/F6 : %u\r\n", ch_1 );

    ch_2 = adc_buf[ 5 ];
    ch_2 <<= 8;
    ch_2 |= adc_buf[ 4 ];
    log_printf( &logger, " ADC2/F7 : %u\r\n", ch_2 );

    ch_3 = adc_buf[ 7 ];
    ch_3 <<= 8;
    ch_3 |= adc_buf[ 6 ];
    log_printf( &logger, " ADC3/F8 : %u\r\n", ch_3 );

    ch_4 = adc_buf[ 9 ];
    ch_4 <<= 8;
    ch_4 |= adc_buf[ 8 ];
    log_printf( &logger, " ADC4/Clear : %u\r\n", ch_4 );

    f_val = spectrometer_flicker_detection( &spectrometer );

    log_printf( &logger, " Flicker : " );
    if ( f_val == SPECTROMETER_UNKNOWN_FREQ )
    {
        log_printf( &logger, "unknown\r\n" );
    }
    else if ( f_val == SPECTROMETER_DETECTED_100_HZ )
    {
        log_printf( &logger, "100 Hz detected\r\n" );
    }
    else if ( f_val == SPECTROMETER_DETECTED_120_HZ )
    {
        log_printf( &logger, "120 Hz detected\r\n" );
    }
    else
    {
        log_printf( &logger, "Error in reading\r\n" );
    }

    log_printf( &logger, "-----------------\r\n" );
    Delay_ms( 1000 );
}

void main ( void )
{
    application_init( );

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


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

Additional Support

Resources