Bring unprecedented accuracy and versatility to voltage control with MCP4361 and ATmega324P

Ohm-inous possibilities

Published Aug 21, 2023

Click board™

DIGI POT 5 click

Dev. board

EasyAVR v7

Compiler

NECTO Studio

MCU

ATmega324P

Replace cumbersome mechanical potentiometers with our digital alternative, improving reliability, durability, and allowing for advanced automation

Hardware Overview

How does it work?

DIGI POT 5 Click is based on the MCP4361, an 8-bit quad digital potentiometer from Microchip. This is a very versatile quad-digital potentiometer controlled via the SPI interface. The device has four integrated digital potentiometer sections, which consist of a string of resistors - serially connected, with digitally controlled analog switches, used to connect the wiper terminal position. The wiper position value of 0x000h corresponds to the lower end of the resistor ladder, while 0x100h corresponds to the upper end. These values can be written in the volatile wiper registers, with one address for each of the four wipers. Each of the four wipers can be controlled in several ways. Writing data directly to the volatile wiper register will move the wiper to the specified location. Wiper value can also be incremented or decremented by writing data to the incrementing or decrementing registers, providing that the wiper is not locked and that the wiper register value is not 0x000h (prevents further decrease) or above 0x100h (prevents further increase). Increasing and decreasing commands will be disregarded if the wiper register is set to a value greater than 0x100h. The incrementing and decrementing registers allow for less overhead if the wiper position has to be increased or decreased, making it easy to interface with the

rotary encoder applications, for example. The MCP4361 also features the WiperLock™ function, which prevents further changes in the wiper position, effectively locking the wiper in place. The CS pin must be pulled beyond the predefined voltage level threshold (8.5V to 12.5V) to enable this functionality. When this happens, the device enters the high voltage communication mode (HV mode), and the WiperLock™ functions can be accessed. The click board has a dedicated high-voltage input pad (VIHH), which can drive the CS pin with the appropriate voltage level when the HV mode is required. The resistor ladder network can be completely turned off by writing to the terminal control registers. This effectively disconnects the potentiometer terminals from a circuit, reducing the power consumption of the MCP4361 and the electrical circuit the IC is used in. The terminal control registers can switch the wiper terminals and the two resistor terminals separately. A STATUS register is also used for storing various status-related information, such as the WiperLock™ status, EEPROM writes to protect the status, and so on. The EEPROM memory holds the wiper data, even after the power is down. Several (five) general purpose 9bit addresses and 4 NV wiper register addresses are copied to the wiper register addresses after the restart or

power-up, allowing the device to resume the wiper position from a previous, stored state. By default, the data registers are zeroed out, while the NV wiper registers hold the middle scale position for the wiper. DIGI POT 5 Click has one 2x10 pin standard, 2.54mm pitch header connecting the four potentiometer terminals. There are three SMD jumpers onboard: The SMD jumper labeled WP is used to set the WP pin state of the MCP4361. The WP pin is used as the hardware EEPROM write protection and a software WP bit of the STATUS register (writable in HV mode only). The hardware WP pin and the software WP bit must be set to disabled mode to write to EEPROM. The SMD jumper labeled PWR SEL selects the power supply voltage - 3.3V or 5V. This also affects the logic voltage levels used for the SPI communication. The SMD jumper labeled CS SEL selects the CS pin voltage level. If the HV mode is required, this jumper should be moved to the VIHH position so that the externally connected 8.5V to 12.5V power source can pull up the CS pin. If HV mode is not required, this SMD jumper should stay at the default position (CS). Note that while in the HV mode, the CS pin is used the same way as with the regular SPI communication, with a difference in logical levels - the HV mode logical HIGH is at least 8.5V.

DIGI POT 5 click hardware overview image

Features overview

Development board

EasyAVR v7 is the seventh generation of AVR development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 16-bit AVR microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB. 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, EasyAVR v7 allows you to connect accessory boards, sensors, and custom electronics more

efficiently than ever. Each part of the EasyAVR 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 a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V 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 which cover a wide range of 16-bit AVR MCUs. EasyAVR 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

AVR

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

2048

Used MCU Pins

mikroBUS™ mapper

Reset

PA6

RST

SPI Chip Select

PA5

SPI Clock

PB7

SCK

SPI Data OUT

PB6

MISO

SPI Data IN

PB5

MOSI

Power Supply

3.3V

Ground

GND

PWM

INT

SCL

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

EasyAVR v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyAVR v7 as your development board.

NECTO Output Selection Step Image hardware assembly

In the advanced settings, pay special attention to the Redirect standard output field. By default, it is set to Application output as the method of displaying final results. To show results via a UART terminal, select the “UART” option in that field and click the “SAVE” button. You will be returned to the Compiler field, and now you can move on to the next step by pressing the “NEXT” button.

GNSS2 Click front image hardware assembly

GNSS2 Click complete accessories setup image hardware assembly

EasyAVR v7 Access DIP MB 1 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

EasyPIC PRO v7a Display Selection 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 DIGI POT 5 Click driver.

Key functions:

digipot5_generic_write - Generic Write function
digipot5_generic_read - Generic Read function
digipot5_increment_wiper - Increment Wiper 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 DIGI POT 5 Click example
 *
 * # Description
 * This example demonstrates the use of the DIGI POT 5 click board.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes all necessary peripherals and pins used for the DIGI POT 5 click.
 * Also allows the device to be reset and configured to enable all wipers (4).
 * UART console module will be initialized also in this function.
 *
 * ## Application Task
 * Demonstrates the use of click driver functions by performing a control of
 * the all wipers positions. By checking the uart console, user can be informed
 * about the all current wipers positions.
 *
 * *note:*
 * Increment/decrement command can be issued only to volatile wiper locations.
 *
 * \author Nemanja Medakovic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "digipot5.h"


// ------------------------------------------------------------------ VARIABLES

static digipot5_t digipot5;
static log_t console;
static uint8_t i;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init( void )
{
    digipot5_cfg_t digipot5_cfg;
    log_cfg_t console_cfg;

    //  Click initialization.
    digipot5_cfg_setup( &digipot5_cfg );
    DIGIPOT5_MAP_MIKROBUS( digipot5_cfg, MIKROBUS_1 );
    digipot5_init( &digipot5, &digipot5_cfg );
    digipot5_reset( &digipot5 );
    digipot5_default_cfg( &digipot5 );

    /** 
     * 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( console_cfg );
    log_init( &console, &console_cfg );
    log_printf( &console, "***  DIGI POT 5 Initialization Done  ***\r\n" );
    log_printf( &console, "****************************************\r\n" );
}

void application_task( void )
{
    log_printf( &console, "* Setting wiper 0 to zero scale.\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER0_VOL,
                            DIGIPOT5_RES_ZEROSCALE );
    log_printf( &console, "* Setting wiper 1 to 3k Ohm.\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER1_VOL,
                            DIGIPOT5_RES_3KOHM );
    log_printf( &console, "* Setting wiper 2 to half scale (5k Ohm).\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER2_VOL,
                            DIGIPOT5_RES_5KOHM_HALFSCALE );
    log_printf( &console, "* Setting wiper 3 to full scale (10k Ohm).\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER3_VOL,
                            DIGIPOT5_RES_10KOHM_FULLSCALE );

    Delay_ms( 3000 );
    log_printf( &console, "* Decrementing wiper 3 by 5 steps.\r\n" );
    for ( i = 0; i < 5; i++ )
    {
        digipot5_decrement_wiper( &digipot5, DIGIPOT5_REG_WIPER3_VOL );
    }

    Delay_ms( 3000 );
    log_printf( &console, "* Incrementing wiper 0 by 10 steps.\r\n" );
    for ( i = 0; i < 10; i++ )
    {
        digipot5_increment_wiper( &digipot5, DIGIPOT5_REG_WIPER0_VOL );
    }

    Delay_ms( 3000 );
    log_printf( &console, "* Setting wiper 0 to 2k Ohm.\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER0_VOL,
                            DIGIPOT5_RES_2KOHM );
    log_printf( &console, "* Setting wiper 1 to 2k Ohm.\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER1_VOL,
                            DIGIPOT5_RES_2KOHM );
    log_printf( &console, "* Setting wiper 2 to 2k Ohm.\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER2_VOL,
                            DIGIPOT5_RES_2KOHM );
    log_printf( &console, "* Setting wiper 3 to 2k Ohm.\r\n" );
    digipot5_generic_write( &digipot5, DIGIPOT5_REG_WIPER3_VOL,
                            DIGIPOT5_RES_2KOHM );

    Delay_ms( 3000 );
    log_printf( &console, "****************************************\r\n" );
}

void main( void )
{
    application_init( );

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


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