Powering a sustainable future using BQ25570 and PIC18F87J60

Efficient power, happy planet!

Published Jun 08, 2023

Click board™

Solar energy click

Dev. board

EasyPIC PRO v7

Compiler

NECTO Studio

MCU

PIC18F87J60

Provide power to your solution using the solar panel and charge the LiPo rechargeable battery efficiently

Hardware Overview

How does it work?

Solar energy Click is based on the BQ25570, a nano-power high-efficiency boost charger, and buck converter from Texas Instruments, designed to work with very low-power energy harvesting elements. It can both provide power to the connected external load and charge the LiPo rechargeable battery using the solar panel as the photovoltaic element - employing its energy harvesting capabilities. The connected load will be powered on from the connected LiPo battery or the supercapacitor soldered on board. When the battery voltage drops under 2.85V, the interrupt pin (routed to the mikroBUS™ INT pin) will be driven to a LOW logic state. The integrated nano-power management unit provides the proper

charging conditions for the battery. When the battery is charged up to 3.25V due to the hysteresis set with the voltage divider resistors, the INT pin will again go to a HIGH logic state. Also, thanks to the nano-power management unit, the battery will not get overcharged above 4.06V. The click board™ provides 2.6V/100mA for the connected external load on the output terminal. The internal supercapacitor will be used as the energy storage element when the battery is not connected. This is useful for continuous powering up of very low-power applications, as the supercapacitor should be able to provide power continuously since it will get recharged by the solar panel before the load drains it out.

The internal converter will be disabled if the storage element voltage drops under the internally set under-voltage level of 1.95V, preventing the damage of completely draining out the connected storage element. In addition to the INT pin, there are two more pins of the BQ25570 routed to the mikroBUS™, used to enable the BQ25570 internal sections (EN) and to enable the power output for the connected load (OUT). Setting the EN pin to the LOW logic level will allow the BQ25570 internal sections and the power charger features, while the HIGH logic level on the OUT pin will enable the power output for the connected load.

Features overview

Development board

EasyPIC PRO 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 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, such as switches, buttons, indicators, connectors, and others, in one place. With two different connectors for each port, EasyPIC PRO v7 allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of the EasyPIC PRO 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 a wide range of 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, RS-232, and Ethernet are also included, including the well-established

mikroBUS™ standard, two display options (graphical and character-based LCD), and a standard TQFP socket for the seventh-generation MCU cards. This socket covers a wide range of 8-bit PIC MCUs, from PIC18LF, PIC16LF, PIC16F, and PIC18F families. EasyPIC PRO 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

Type

7th Generation

Architecture

PIC

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

3808

You complete me!

Accessories

Li-Polymer Battery is the ideal solution for devices that demand a dependable and long-lasting power supply while emphasizing mobility. Its compatibility with mikromedia boards ensures easy integration without additional modifications. With a voltage output of 3.7V, the battery meets the standard requirements of many electronic devices. Additionally, boasting a capacity of 2000mAh, it can store a substantial amount of energy, providing sustained power for extended periods. This feature minimizes the need for frequent recharging or replacement. Overall, the Li-Polymer Battery is a reliable and autonomous power source, ideally suited for devices requiring a stable and enduring energy solution. You can find a more extensive choice of Li-Polymer batteries in our offer.

Solar Panel offers an efficient alternative powering solution for your device, harnessing the remarkable photoelectric effect to generate electricity when exposed to sunlight. Comprising monocrystalline silicon solar cells encapsulated with PC film lamination, this panel ensures durability and protection from environmental elements. The magic lies in the photoelectric effect, where sunlight excites electrons in the silicon cells, creating an electric current. The panel's construction optimizes sunlight absorption and conversion, enabling it to generate a minimum output of 4.0V. It can produce electrical power under a maximum load of 100mA, making it ideal for various applications. This solar panel offers a sustainable and eco-friendly approach, providing a renewable energy source that reduces reliance on conventional power grids and promotes environmental consciousness.

Used MCU Pins

mikroBUS™ mapper

Buck Enable

RA0

RST

Chip Enable

RE0

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

Battery OK Indication

RB0

INT

SCL

SDA

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

EasyPIC PRO v7 front image hardware assembly

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

GNSS2 Click front image hardware assembly

EasyPIC PRO v7 MCUcard with PIC18F8520 front image hardware assembly

GNSS2 Click complete accessories setup image hardware assembly

EasyPIC PRO v7 Access MB 1 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

EasyPIC PRO v7a MCU Selection Necto Step hardware assembly

EasyPIC PRO v7a Display Selection Necto Step 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 Solar energy Click driver.

Key functions:

solarenergy_charge_enable - Charge enable function
solarenergy_charge_disable - Charge disable functions
solarenergy_check_indicator - Battery good indicator functions

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 SOLAR ENERGY Click example
 * 
 * # Description
 * This application charge the batery when is empty.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initialization driver enables - GPIO and start to write log.
 * 
 * ## Application Task  
 * This is an example which demonstrates the use of Solar Energy Click board.
 * The following example will charge the battery if it is empty, and stop charging
 * when the battery is full. When battery full status is detected, the device is
 * disabled, but will check battery status every 10 seconds.
 * Results are being sent to the Usart Terminal where you can track their changes.
 *
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "solarenergy.h"

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

static solarenergy_t solarenergy;
static log_t logger;

void application_init ( void )
{
    log_cfg_t log_cfg;
    solarenergy_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.

    solarenergy_cfg_setup( &cfg );
    SOLARENERGY_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    solarenergy_init( &solarenergy, &cfg );

    log_printf( &logger, "   Initialization   \r\n" );
    log_printf( &logger, "--------------------\r\n" );
    log_printf( &logger, " Charge the battery \r\n" );
    log_printf( &logger, "--------------------\r\n" );
    Delay_ms( 1000 );
}

void application_task ( void )
{
    if ( solarenergy_check_indicator( &solarenergy ) )
    {
        solarenergy_charge_disable( &solarenergy );
        Delay_ms ( 10000 );
    }
    else
    {
        solarenergy_charge_enable( &solarenergy );
    }
}

void main ( void )
{
    application_init( );

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


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