Intermediate
30 min

Measure force or weight of an object with ADS1230 and PIC18F4620

Force meter

Load Cell 7 Click with EasyPIC v7

Published Mar 04, 2023

Click board™

Load Cell 7 Click

Development board

EasyPIC v7

Compiler

NECTO Studio

MCU

PIC18F4620

Complete front-end for bridge sensing applications

A

A

Hardware Overview

How does it work?

Load Cell 7 Click is based on the ADS1230, a high accuracy, low noise, and low power 20-bit ΣΔ ADC with an outstanding noise performance from Texas Instruments. It includes a low-noise PGA, internal oscillator, third-order delta-sigma (ΔΣ) modulator, and fourth-order digital filter, thus providing a complete front-end solution for bridge sensor applications. The ADS1230 is easy to configure, and all digital control is accomplished through dedicated pins; there are no programmable registers. The conversions from the ADS1230 are sent to the MCU through SPI serial interface, with the digital information converted to weight. The low-noise PGA has a selectable gain,

performed by an onboard SMD jumper labeled as GAIN SEL to an appropriate position marked as 64 and 128, supporting a full-scale differential input of ±39mV or ±19.5mV, respectively. Besides, data can be output at 10SPS for excellent 50Hz and 60Hz rejection or at 80SPS when higher speeds are needed. The onboard SMD jumper labeled SPS SEL can select this feature, placing it in an appropriate position marked as 10 and 80. The ADS1230 can be put in a low-power standby mode or shut off completely in power-down mode. This Click board™ uses the 4-wire load cell configuration, with two sense pins and two output connections. The load cell differential S lines connected to

the AD7780 reference inputs create a ratiometric configuration immune to low-frequency power supply excitation voltage changes. Those sense pins are connected to the high and low sides of the Wheatstone bridge, where voltage can be accurately measured, regardless of the voltage drop due to the wiring resistance. 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. 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.

Load Cell 7 Click top side image
Load Cell 7 Click lateral side image
Load Cell 7 Click bottom side image

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.

EasyPIC v7 horizontal image

Microcontroller Overview

MCU Card / MCU

PIC18F4620

Architecture

PIC

MCU Memory (KB)

64

Silicon Vendor

Microchip

Pin count

40

RAM (Bytes)

3968

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
SPI Chip Select
RE0
CS
SPI Clock
RC3
SCK
SPI Data OUT
RC4
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
NC
NC
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

Load Cell 7 Click Schematic 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.

EasyPIC v7 front image hardware assembly
GNSS2 Click front image hardware assembly
MCU DIP 40 hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
EasyPIC v7 Access 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 DIP image step 7 hardware assembly
EasyPIC PRO v7a Display Selection Necto Step 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 Load Cell 7 Click driver.

Key functions:

  • loadcell7_tare_scale This function calculates the @b ctx->tare_scale which is the raw ADC readings of the empty container.

  • loadcell7_calibrate_weight This function calibrates the weight by calculating the @b ctx->weight_scale for the input calibration weight.

  • loadcell7_get_weight This function calculates the weight of the goods in grams.

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 Load Cell 7 Click example
 *
 * # Description
 * This example demonstrates the use of Load Cell 7 click by measuring the weight
 * in grams of the goods from the load cell sensor connected to the click board.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and reads the tare scale of the empty container, and after
 * that, it calibrates the weight scale with a known calibration weight.
 *
 * ## Application Task
 * Reads the net weight of the goods in grams approximately once per second and logs the
 * results on the USB UART. 
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "loadcell7.h"

// Enter below the weight in grams of the goods with a known weight which 
// you will use to calibrate the scale weight.
#define LOADCELL7_CALIBRATION_WEIGHT_G  1000.0

static loadcell7_t loadcell7;
static log_t logger;

void application_init ( void )
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    loadcell7_cfg_t loadcell7_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 );
    log_info( &logger, " Application Init " );

    // Click initialization.
    loadcell7_cfg_setup( &loadcell7_cfg );
    LOADCELL7_MAP_MIKROBUS( loadcell7_cfg, MIKROBUS_1 );
    if ( SPI_MASTER_ERROR == loadcell7_init( &loadcell7, &loadcell7_cfg ) )
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    log_printf( &logger, " Remove all goods from the scale in the following 5 sec.\r\n");
    Delay_ms ( 5000 );
    log_printf( &logger, " Calculating tare scale...\r\n");
    if ( LOADCELL7_OK == loadcell7_tare_scale ( &loadcell7 ) ) 
    {
        log_printf( &logger, " Tarring complete!\r\n\n");
    }
    else 
    {
        log_error( &logger, " Calculating tare scale.");
        for ( ; ; );
    }
    
    log_printf( &logger, " Place a %ug calibration weight on the scale in the following 5 sec.\r\n", 
                ( uint16_t ) LOADCELL7_CALIBRATION_WEIGHT_G );
    Delay_ms ( 5000 );
    log_printf( &logger, " Calibrating weight...\r\n");
    if ( LOADCELL7_OK == loadcell7_calibrate_weight ( &loadcell7, LOADCELL7_CALIBRATION_WEIGHT_G ) ) 
    {
        log_printf( &logger, " Calibration complete!\r\n\n");
    }
    else 
    {
        log_error( &logger, " Calibrating weight.");
        for ( ; ; );
    }

    log_info( &logger, " Application Task " );
}

void application_task ( void )
{
    float weight;
    if ( LOADCELL7_OK == loadcell7_get_weight ( &loadcell7, &weight ) ) 
    {
        log_printf(&logger, " Weight : %.2f g\r\n", weight );
    }
}

void main ( void )
{
    application_init( );

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

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

Additional Support

Resources