Set the standard for ultra-low voltage comparison using MAX40000 and PIC18F26K20

Ultra-efficient voltage comparator

Published Nov 01, 2023

Click board™

Nano Power 2 Click

Dev Board

EasyPIC v8

Compiler

NECTO Studio

MCU

PIC18F26K20

Detecting voltage differences becomes effortless with our nanoPower voltage comparator, offering efficient monitoring for various applications

Hardware Overview

How does it work?

Nano Power 2 Click is based on the MAX40000, a nanoPower comparator with built-in reference from Analog Devices. This company offers several variants of the same IC, of which the used IC variant offers reference voltage of 1.2V on one of its pins. This reference voltage can be used at the comparator input, providing an accurate reference voltage throughout the fully operational temperature range, if required by the custom application. The IC itself requires a very low number of external components. It has two input pins, used as the comparator inputs. Each of these inputs can use -0.2V up to VCC + 0.2V. The VCC is the power supply voltage, and it can be selected via the SMD jumper labeled as LOGIC, between the 3.3V and 5V rails from the mikroBUS™. One of the comparator inputs, labeled as IM on the MAX40000 IC, is routable to either the onboard potentiometer (P1) or the REF pin of the IC, which provides the referent voltage of 1.2V. The routing can be done by another SMD jumper, labeled as REF SEL. The second comparator input (labeled as IP on the MAX40000 IC) is routed to the second

onboard potentiometer (P2). Both potentiometers can be used to set any voltage between the GND and VCC, which is selected by the LOGIC jumper, as described above. As mentioned before, the comparator has two inputs. One of them it is the inverting input and it is labeled as IM. The other input is a non-inverting input, labeled as IP. When the IP voltage becomes higher than the IM voltage, the output state becomes logic HIGH; otherwise, the output is set to a LOW state. A special case is when both voltages are very close, or at the same level, at any given moment. This would result in an appearance of oscillation at the output due to noise or parasitic feedback. To cope with this problem, an internal hysteresis of ±2.5mV is applied. The output of the MAX40000 IC is routed to the mikroBUS™ INT pin, labeled as OUT on the Click board™. The output stage employs a unique break-before-make topology, capable of rail-to-rail operation with up to ±2mA loads. The output stage also uses a unique design, which minimizes supply current surges when the switching occurs, resulting in very clean output

and low EM radiation. The MAX40000 has a push-pull output stage topology, which can both sink and source the current. Working with the Nano Power 2 click is very easy and straightforward. Only a single pin is used, which can be used to either trigger an interrupt (therefore it is routed to the INT pin), or its status can be read via the input pin of the host MCU. However, MikroElektronika provides a library that contains a function which can be used for simplified control of the Nano Power 2 click. The library also contains an example application, which demonstrates the use of the function. This example application can be used as a reference for custom designs. 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.

Nano Power 2 Click hardware overview image

Features overview

Development board

EasyPIC 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. 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 v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the EasyPIC 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 CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC 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.

Microcontroller Overview

MCU Card / MCU

Architecture

PIC

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

3936

Used MCU Pins

mikroBUS™ mapper

RST

SCK

MISO

MOSI

3.3V

Ground

GND

PWM

Comparator Output

RB1

INT

SCL

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

EasyPIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v8 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 v8 28pin-DIP - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

Track your results in real time

Application Output

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for Nano Power 2 Click driver.

Key functions:

nanopower2_check_output - Function gets output voltage from comparator

Open Source

Code example

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * \file 
 * \brief Nano Power 2 Click example
 * 
 * # Description
 * This application logs the comparators output value on USBUART.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes GPIO driver.
 * 
 * ## Application Task  
 * Checks the comparator's output and logs output value on USBUART.
 * 
 * \author Petar Suknjaja
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "nanopower2.h"

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

static nanopower2_t nanopower2;
static log_t logger;

uint8_t out_check;
uint8_t out_check_prev;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    nanopower2_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.
    nanopower2_cfg_setup( &cfg );
    NANOPOWER2_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    nanopower2_init( &nanopower2, &cfg );

    log_printf( &logger, "NANO POWER 2 is initialized\r\n" );
    out_check_prev = 2;
}

void application_task ( void )
{
    out_check = nanopower2_check_output( &nanopower2 );
    if ( out_check != out_check_prev )
    {
        log_printf( &logger, "OUT is: %d\r\n", ( uint16_t ) out_check );

        out_check_prev = out_check;
    }
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}


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