Upgrade your projects with accurate force sensing using 34-00004 and STM32F091RC
Capturing forces with precision
Published Feb 26, 2024
Click board™
Force 3 Click
Dev Board
Nucleo-64 with STM32F091RC MCU
Compiler
NECTO Studio
MCU
STM32F091RC
Gain real-time insights into applied forces for improved analysis
A
A
Hardware Overview
How does it work?
Force 3 Click is based on the FSR 400 series 34-00004 single zone Force Sensing Resistor IC from Interlink Electronics. Force-sensing resistors consist of a conductive polymer, which predictably changes resistance following applying force to its surface. As the force on the sensor is increased, the resistance is decreased. This thin sensor comprises two membranes separated by a spacer around the edges. The top layer of the sensor consists of the area of the force-sensitive layer on the flexible film, while the bottom layer comprises conductive circuit traces on the flexible film. When pressed, the gap between the two membranes gets closed. This shorts the two membranes together with a resistance proportional to an applied force. Force 3 Click also contains all the necessary circuitry
required to obtain precise measurements from the sensor. It communicates with the MCU using the MCP3221, a low-power 12-bit resolution A/D converter with an I2C interface. Data on the I2C bus can be transferred at rates of up to 100 kbit/s in the standard mode and up to 400 kbit/s in the fast mode. Maximum sample rates of 22.3 kSPS are possible with the MCP3221 in a continuous-conversion mode and SCL clock rate of 400 kHz. The sensor is placed in a voltage divider configuration with a fixed resistor R2 (10k). The output voltage is measured across resistor R2 and then sent to the analog pin of the A/D converter MCP3221. Output voltage value was calculated using the voltage divider formula, which was later used in the Test Example to accurately determine
the strength of the applied force. The Test Example is made in such a way that, based on the value of the applied force, it is possible to obtain four output values: Light Touch, Weak Squeeze, Medium Squeeze, and Strong Squeeze. This Click Board™ uses the I2C communication interface. It is designed to be operated only with 3.3V logic levels. A proper logic voltage level conversion should be performed before the Click board™ is used with MCUs with logic levels of 5V. More information about the 34-00004 Force Sensing Resistor can be found in the attached datasheet. However, the Click board™ comes equipped with a library that contains easy-to-use functions and a usage example that may be used as a reference for the development.
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.
Microcontroller Overview
MCU Card / MCU
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.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Nucleo-64 with STM32F091RC MCU as your development board.
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 Force 3 Click driver.
Key functions:
force3_read_raw_data- Read 12bit raw data
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 Force3 Click example
*
* # Description
* This application demonstrates the use of Force 3 click board.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver and makes an initial log.
*
* ## Application Task
* Reads the sensor raw data and displays it on the USB UART.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "force3.h"
// ------------------------------------------------------------------ VARIABLES
static force3_t force3;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
force3_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.
force3_cfg_setup( &cfg );
FORCE3_MAP_MIKROBUS( cfg, MIKROBUS_1 );
force3_init( &force3, &cfg );
}
void application_task ( void )
{
uint16_t raw_data;
raw_data = force3_read_raw_data( &force3 );
log_printf( &logger, "Raw data: %d \r\n", raw_data );
if ( ( raw_data > 5 ) && ( raw_data <= 200 ) )
{
log_printf( &logger, ">> Light touch \r\n" );
}
else if ( ( raw_data > 200 ) && ( raw_data <= 500 ) )
{
log_printf( &logger, ">> Light squeeze \r\n" );
}
else if ( ( raw_data > 500 ) && ( raw_data <= 800 ) )
{
log_printf( &logger, ">> Medium squeeze \r\n" );
}
else if ( raw_data > 800 )
{
log_printf( &logger, ">> Big squeeze \r\n" );
}
log_printf( &logger, "----------------------\r\n" );
Delay_ms( 1000 );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
