Measure force or weight of an object with ADS1230 and PIC18F4620
Force meter
Published Mar 04, 2023
Click board™
Load Cell 7 Click
Dev Board
EasyPIC v7
Compiler
NECTO Studio
MCU
PIC18F4620
Complete front-end for bridge sensing applications
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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.
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.
Microcontroller Overview
MCU Card / MCU
Architecture
PIC
MCU Memory (KB)
64
Silicon Vendor
Microchip
Pin count
40
RAM (Bytes)
3968
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the EasyPIC v7 as your development board.
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.
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.
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".
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.
Software Support
Library Description
This library contains API for Load Cell 7 Click driver.
Key functions:
loadcell7_tare_scaleThis function calculates the @b ctx->tare_scale which is the raw ADC readings of the empty container.loadcell7_calibrate_weightThis function calibrates the weight by calculating the @b ctx->weight_scale for the input calibration weight.loadcell7_get_weightThis 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
