Measure how much electrical current is flowing through a circuit with INA196 and PIC18LF47K40

Current sensing has never been this electrifying!

Published Jun 19, 2023

Click board™

Current Click

Dev. board

EasyPIC v8

Compiler

NECTO Studio

MCU

PIC18LF47K40

Achieve precise current measurements (from 2mA up to 2Amps) by sensing voltage drops across the added shunt resistor

Hardware Overview

How does it work?

Current Click is based on the INA196, a current shunt monitor from Texas Instruments. The INA196 has a voltage output that can sense drops across shunts at common-mode voltages from −16V to +80V, independent of its supply voltage. It is also characterized by a gain of 20V/V and 500kHz bandwidth, simplifying current control loops' use across a vast temperature range, making it suitable for many consumer, enterprise, telecom, and automotive applications. This Click board™ measures current values in various bands. The board receives current from the output circuit connected to IN(+) and OUT(-) pins of the first

screw terminal, where the INA196 converts this current into a voltage, while the second screw terminal is used for the external shunt connection. Users need to provide the shunt of the appropriate value allowing the measurement up to 2048mA, based on the reference voltage set by MAX6106. Therefore, four shunts with different values are provided in the package (0.05, 0.2, 1, and 10Ω). The output signal of the INA196 can be converted to a digital value using MCP3201, a successive approximation A/D converter with a 12-bit resolution from Microchip using a 3-wire SPI 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 OUTPUT, placing it in an appropriate position marked as AN or ADC. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the PWRSEL 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.

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)

128

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

3728

Used MCU Pins

mikroBUS™ mapper

Analog Output

RA2

RST

SPI Chip Select

RE0

SPI Clock

RC3

SCK

SPI Data OUT

RC4

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

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.

GNSS2 Click front image hardware assembly

GNSS2 Click complete accessories setup image hardware assembly

EasyPIC v8 Access DIPMB 1 - 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 Current Click driver.

Key functions:

current_get_current_data - This function calculates the current in mA

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 Current Click example
 * 
 * # Description
 * This is an example that shows the capabilities of the Current click board 
 * by measuring current in miliampers. Current click board can be used to safely
 * measure DC current in the range of 2-2048mA depending on shunt resistor.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initalizes SPI, LOG and click drivers.
 * 
 * ## Application Task  
 * Measures DC current and displays the results on USB UART each second.
 * 
 * @note
 * Shunt resistor used in the example covers 4 default values (0.05 Ohm, 0.2 Ohm, 1 Ohm, 10 Ohm).
 * To operate in linear range of INA196 check table bellow for shunt selection.
 * |------------------------------------|
 * | Rshunt  | Imin [mA]  | Imax  [mA]  |
 * |------------------------------------|
 * |   0.05  |    400     |   2048      |
 * |   0.2   |    100     |    512      |
 * |   1     |     20     |    102      |
 * |  10     |      2     |     10      |
 * --------------------------------------
 * 
 * \author Jovan Stajkovic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "current.h"

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

static current_t current;
static log_t logger;
static float curr;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    current_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.

    current_cfg_setup( &cfg );
    CURRENT_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    current_init( &current, &cfg );
    log_printf( &logger, "-----------------------\r\n" );
    log_printf( &logger, "    Current  Click     \r\n" );
    log_printf( &logger, "-----------------------\r\n" );
}

void application_task ( void )
{
    curr = current_get_current_data( &current, CURRENT_RSHUNT_0_05 );
    
    if ( curr == CURRENT_OUT_OF_RANGE )
    {
        log_printf( &logger, "Out of range!\r\n" );
    }
    else
    {
       log_printf( &logger, " Current: %.2f mA\r\n", curr );
    }
    
    log_printf( &logger, "-----------------------\r\n" );
    Delay_ms( 1000 );
}

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

    return 0;
}

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