Intermediate
30 min

Unlock data-driven decisions with precise weight measurements using AD7780 and STM32F091RC

Weight matters, accuracy counts

Load Cell 5 Click with Nucleo-64 with STM32F091RC MCU

Published Feb 26, 2024

Click board™

Load Cell 5 Click

Dev. board

Nucleo-64 with STM32F091RC MCU

Compiler

NECTO Studio

MCU

STM32F091RC

Achieve your health goals with accurate weight tracking for personalized progress

A

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Hardware Overview

How does it work?

Load Cell 5 Click is based on the AD7780, a pin programmable, low power, low drift 24-bit ΣΔ ADC from Analog Devices that includes a PGA and uses an internal clock. The AD7780 typically consumes only 330μA and simplifies this weigh scale design since most of the system building blocks are already on the chip. The AD7780 has two filter options selectable via FIL pin(low state - 16.7Hz, high state - 10Hz) and a Power-Down Mode, allowing the user to switch off the power to the bridge sensor and power down the AD7780 when not converting, increasing the battery life. Since the AD7780 provides an integrated solution for weighing scales, it interfaces directly with the load cell. The only required external components, which are also on the Click board™, are filters on the analog inputs and capacitors on the reference pins for EMC purposes. The low-level signal from the load cell is amplified by the AD7780's internal PGA programmed via the PWM pin of the mikroBUS™ socket, labeled as GN, to operate with

a gain of 128 or 1. The conversions from the AD7780 are then sent to the MCU through the SPI serial interface, where the digital information is converted to weight. This Click board™ uses the 6-wire load cell configuration, which has two sense pins, ground, power supply, and two output connections. The load cell differential SENSE lines connected to the AD7780 reference inputs create a ratiometric configuration immune to low-frequency changes in the power supply excitation voltage. 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. The AD7780 has separate analog and digital power supply pins. The analog and digital power supplies are independent of each other to be different, or the same, potentials achieved with the AVDD SEL jumper. This feature allows selecting the AD7780 power supply between an external power supply (2.7 - 5.25V) and logic

voltage levels supplied via mikroBUS™ rails. Load Cell 5 Click communicates with MCU using a standard SPI interface with a dual-purpose DOUT/RDY line. This line can function as a regular data output pin for the SPI interface or as a data-ready pin (interrupt) labeled as RDY and routed on the INT pin of the mikroBUS socket. Also, it uses the RST pin on the mikroBUS™ socket, which performs the Hardware Reset function by putting this pin in a logic low state, and a blue diode labeled as ACTIVE is used to indicate the device's Active Operational Status. 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.

Load Cell 5 Click hardware overview image

Features overview

Development board

Nucleo-64 with STM32F091RC MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin

headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is

provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.

Nucleo 64 with STM32F091RC MCU double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

ARM Cortex-M0

MCU Memory (KB)

256

Silicon Vendor

STMicroelectronics

Pin count

64

RAM (Bytes)

32768

You complete me!

Accessories

Click Shield for Nucleo-64 comes equipped with two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the STM32 Nucleo-64 board with no effort. This way, Mikroe allows its users to add any functionality from our ever-growing range of Click boards™, such as WiFi, GSM, GPS, Bluetooth, ZigBee, environmental sensors, LEDs, speech recognition, motor control, movement sensors, and many more. More than 1537 Click boards™, which can be stacked and integrated, are at your disposal. The STM32 Nucleo-64 boards are based on the microcontrollers in 64-pin packages, a 32-bit MCU with an ARM Cortex M4 processor operating at 84MHz, 512Kb Flash, and 96KB SRAM, divided into two regions where the top section represents the ST-Link/V2 debugger and programmer while the bottom section of the board is an actual development board. These boards are controlled and powered conveniently through a USB connection to program and efficiently debug the Nucleo-64 board out of the box, with an additional USB cable connected to the USB mini port on the board. Most of the STM32 microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the STM32 Nucleo-64 board with our Click Shield for Nucleo-64, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.

Click Shield for Nucleo-64 accessories 1 image

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
Reset
PC12
RST
Filter Selection
PB12
CS
SPI Clock
PB3
SCK
SPI Data OUT
PB4
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
Gain Selection
PC8
PWM
Interrupt / Data Ready
PC14
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

Click board™ Schematic

Load Cell 5 Click Schematic schematic

Step by step

Project assembly

Click Shield for Nucleo-64 accessories 1 image hardware assembly

Start by selecting your development board and Click board™. Begin with the Nucleo-64 with STM32F091RC MCU as your development board.

Click Shield for Nucleo-64 accessories 1 image hardware assembly
Nucleo 64 with STM32F401RE MCU front image hardware assembly
LTE IoT 5 Click front image hardware assembly
Prog-cut hardware assembly
LTE IoT 5 Click complete accessories setup image hardware assembly
Nucleo-64 with STM32XXX MCU Access MB 1 Mini B Conn - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
Clicker 4 for STM32F4 HA MCU Step hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image 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 Load Cell 5 Click driver.

Key functions:

  • loadcell5_set_power_mode - Load Cell 5 set power mode function

  • loadcell5_read_adc - Load Cell 5 reading ADC data function

  • loadcell5_get_weight - Load Cell 5 get weight function

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 main.c
 * @brief LoadCell5 Click example
 *
 * # Description
 * This library contains API for Load Cell 5 Click driver.
 * The library initializes and defines the SPI bus drivers to read status and ADC data. 
 * The library also includes a function for tare, calibration and weight measurement.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * The initialization of SPI module, log UART, and additional pins
 * and performs the power on. Sets tare the scale, calibrate scale 
 * and start measurements. 
 *
 * ## Application Task
 * This is an example that demonstrates the use of the Load Cell 5 click board.
 * The Load Cell 5 click board can be used to measure weight,
 * shows the measurement of scales in grams [ g ].
 * Results are being sent to the Usart Terminal where you can track their changes.
 *
 * @author Nenad Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "loadcell5.h"

static loadcell5_t loadcell5;
static log_t logger;

static uint8_t status_val;
static uint32_t adc_val;

static loadcell5_data_t cell_data;
static float weight_val;

void application_init ( void ) {
    log_cfg_t log_cfg;  /**< Logger config object. */
    loadcell5_cfg_t loadcell5_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.

    loadcell5_cfg_setup( &loadcell5_cfg );
    LOADCELL5_MAP_MIKROBUS( loadcell5_cfg, MIKROBUS_1 );
    err_t init_flag  = loadcell5_init( &loadcell5, &loadcell5_cfg );
    if ( init_flag == SPI_MASTER_ERROR ) {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );
    }

    loadcell5_default_cfg ( &loadcell5 );
    log_info( &logger, " Application Task " );
    Delay_ms( 500 ); 
    
    log_printf( &logger, "-------------------------\r\n");
    log_printf( &logger, "     Tare the scale :    \r\n");
    log_printf( &logger, "- - - - - - - - - - - - -\r\n");
    log_printf( &logger, " >> Remove all object << \r\n");
    log_printf( &logger, "- - - - - - - - - - - - -\r\n");
    log_printf( &logger, " In the following 10 sec \r\n");
    log_printf( &logger, " please remove all object\r\n");
    log_printf( &logger, "     from the scale.     \r\n");
    Delay_ms( 10000 );

    log_printf( &logger, "-------------------------\r\n");
    log_printf( &logger, "    Start tare scales    \r\n");
    loadcell5_tare ( &loadcell5, &cell_data );
    Delay_ms( 500 );

    log_printf( &logger, "-------------------------\r\n");
    log_printf( &logger, "   Tarring is complete   \r\n");
    log_printf( &logger, "-------------------------\r\n");
    log_printf( &logger, "    Calibrate Scale :    \r\n");
    log_printf( &logger, "- - - - - - - - - - - - -\r\n");
    log_printf( &logger, "   >>> Load etalon <<<   \r\n");
    log_printf( &logger, "- - - - - - - - - - - - -\r\n");
    log_printf( &logger, " In the following 10 sec \r\n");
    log_printf( &logger, "place 100g weight etalon\r\n");
    log_printf( &logger, "    on the scale for     \r\n");
    log_printf( &logger, "   calibration purpose.  \r\n");
    Delay_ms( 10000 );

    log_printf( &logger, "-------------------------\r\n");
    log_printf( &logger, "    Start calibration    \r\n");

    if ( loadcell5_calibration ( &loadcell5, LOADCELL5_WEIGHT_100G, &cell_data ) == LOADCELL5_OK ) {
        log_printf( &logger, "-------------------------\r\n");
        log_printf( &logger, "    Calibration  Done    \r\n");

        log_printf( &logger, "- - - - - - - - - - - - -\r\n");
        log_printf( &logger, "  >>> Remove etalon <<<  \r\n");
        log_printf( &logger, "- - - - - - - - - - - - -\r\n");
        log_printf( &logger, " In the following 10 sec \r\n");
        log_printf( &logger, "   remove 100g weight   \r\n");
        log_printf( &logger, "   etalon on the scale.  \r\n");
        Delay_ms( 10000 );
    }
    else {
        log_printf( &logger, "-------------------------\r\n");
        log_printf( &logger, "   Calibration  Error   \r\n");
        for ( ; ; );
    }

    log_printf( &logger, "-------------------------\r\n");
    log_printf( &logger, "   Start measurements :  \r\n");
    log_printf( &logger, "-------------------------\r\n");
}

void application_task ( void ) {   
    weight_val = loadcell5_get_weight( &loadcell5, &cell_data );

    log_printf(&logger, "   Weight : %.2f g\r\n", weight_val );

    Delay_ms( 1000 );
}

void main ( void ) {
    application_init( );

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

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

Additional Support

Resources

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