Fine-tune circuit characteristics easier than ever using MAX5494 and PIC18LF45K22

Taming currents in the digital realm

Published Aug 21, 2023

Click board™

DIGI POT 4 Click

Dev Board

EasyPIC v8

Compiler

NECTO Studio

MCU

PIC18LF45K22

Redesign your approach to precision control by integrating our digital potentiometers, achieving unparalleled customization and stability

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

EasyPIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, EasyPIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the EasyPIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector.

Communication options such as USB-UART, USB DEVICE, and CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC v8 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)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

1536

Used MCU Pins

mikroBUS™ mapper

RST

SPI Chip Select

RE0

SPI Clock

RC3

SCK

MISO

SPI Data IN

RC5

MOSI

Power Supply

3.3V

Ground

GND

PWM

INT

SCL

SDA

Power Supply

Ground

GND

Take a closer look

Schematic

Step by step

Project assembly

EasyPIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v8 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

EasyPIC v8 Access DIPMB 1 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

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 DIGI POT 4 Click driver.

Key functions:

digipot4_write_reg - This function writes data in wiper register and NV register
digipot4_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

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

/*!
 * \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