Fine-tune circuit characteristics easier than ever using MAX5494 and STM32F091RC
Taming currents in the digital realm
Published Feb 26, 2024
Click board™
DIGI POT 4 Click
Dev. board
Nucleo-64 with STM32F091RC MCU
Compiler
NECTO Studio
MCU
STM32F091RC
Redesign your approach to precision control by integrating our digital potentiometers, achieving unparalleled customization and stability
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Hardware Overview
How does it work?
DIGI POT 4 Click is based on the MAX5494, a 10-bit dual, non-volatile, linear taper digital potentiometer from Analog Devices. This IC consists of the control logic and a resistors stream (i.e., 1024 equal resistors serially connected) through which the wiper moves. The end-to-end resistance of the resistors on the used IC is 10KΩ. The wiper movement is done by writing 10-bit data into the wiper registers, resulting in 1024 discrete positions the wiper can take. All three terminals of the digital pot are routed to the IC terminals and the onboard connectors for easy and secure connection to the rest of the circuit.
The MAX5494 contains two such potentiometers routed to the click board™ screw terminals. The voltage drop may occur while switching positions depending on the output impedance to which the wiper is connected. Therefore, it is not recommended to use it as the variable resistor. After the power is on, the content of the EEPROM NV memory will be copied to the volatile RAM, used as the shift register for the wiper position. This volatile memory register directly controls the wiper position. The wiper can be positioned by writing data into this register. The EEPROM NV registers are only written if requested using the
specific write command. This way, the EEPROM lifecycle is prolonged, although it can withstand up to 200000 read/write cycles. All the communication with the control logic of the MAX5494 is done through the SPI, so all the SPI signals are routed to the appropriate mikroBUS™ pins. The CS pin is held high, preventing the SPI communication, so as always - to initialize the SPI communication, the CS pin needs to be pulled LOW by the MCU. Besides two connectors used to connect the potentiometer terminals, the click board™ is equipped with the SMD jumper to choose between the 3.3V or 5V operating voltage.
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 DIGI POT 4 Click driver.
Key functions:
digipot4_write_reg- This function writes data in wiper register and NV registerdigipot4_copy_reg- This function is used to copy the data from the wipers to the NV memory and from the NV memory it wipers
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 DigiPot4 Click example
*
* # Description
* This application is a digitally controlled dual potentiometer.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Driver intialization
*
* ## Application Task
* Set the wiper position.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "digipot4.h"
// ------------------------------------------------------------------ VARIABLES
static digipot4_t digipot4;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( void )
{
log_cfg_t log_cfg;
digipot4_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.
digipot4_cfg_setup( &cfg );
DIGIPOT4_MAP_MIKROBUS( cfg, MIKROBUS_1 );
digipot4_init( &digipot4, &cfg );
}
void application_task ( void )
{
// Task implementation.
digipot4_write_reg( &digipot4, DIGIPOT4_WIPER_REG_1, 0 );
digipot4_write_reg( &digipot4, DIGIPOT4_WIPER_REG_2, 0 );
Delay_1sec( );
digipot4_write_reg( &digipot4, DIGIPOT4_WIPER_REG_1, 512 );
digipot4_write_reg( &digipot4, DIGIPOT4_WIPER_REG_2, 512 );
Delay_1sec( );
digipot4_write_reg( &digipot4, DIGIPOT4_WIPER_REG_1, 1023 );
digipot4_write_reg( &digipot4, DIGIPOT4_WIPER_REG_2, 1023 );
Delay_1sec( );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
