Embrace the future of potentiometers with AD5206 and PIC18F47K42

Simplify voltage adjustments

Published Nov 01, 2023

Click board™

DIGI POT 8 Click

Dev Board

EasyPIC v7

Compiler

NECTO Studio

MCU

PIC18F47K42

From audio equipment to industrial automation, our digital potentiometers offer an electronic means to finely tune parameters, enhancing overall system performance and accuracy

Hardware Overview

How does it work?

DIGI POT 8 Click is based on the AD5206, 6-channel 256-position digitally controlled device that performs the same electronic adjustment function as a potentiometer or variable resistor from Analog Devices. Each channel of the AD5206 contains a fixed resistor with a wiper contact that taps the fixed resistor value of 100kΩ at a point determined by a digital code loaded into the SPI-compatible serial-input register. The resistance between the wiper and either endpoint of the fixed resistor varies linearly concerning the digital code transferred into the variable resistor (VR) latch. The AD5206 also has an internal Power-On preset that places the wiper in a preset midscale condition at the Power-On state. The AD5206 communicates with MCU through the 3-wire

SPI serial interface with a maximum frequency 10MHz. Each VR has its VR latch that holds its programmed resistance value. These VR latches are updated from an internal serial-to-parallel shift register loaded from a standard 3-wire SPI serial-input digital interface. Eleven bits make up the data word clocked into the serial input register. The first three bits are decoded to determine which VR latch is loaded with the last eight bits of the data word when the CS pin of the SPI serial interface returns to a logic high state. In addition to the AD5206 present on the DIGI POT 8, this Click board™ has four 2x3 male headers. Three of them, under the labels A, W, and B, with the appropriate number, represent the corresponding DIGI POT terminal of the AD5206, while

the fourth header, with the label VCC and GND, represents an additional power supply output. Wiper terminal number 6, labeled as W6, also can be used as an auxiliary wiper output, routed to the AN pin of the mikroBUS ™ socket if the wiper back to the mikroBUS™ is required. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it comes equipped with a library containing 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)

128

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

8192

Used MCU Pins

mikroBUS™ mapper

Wiper Output

RA2

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

Ground

GND

Take a closer look

Schematic

Step by step

Project assembly

EasyPIC v7 front image hardware assembly

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

EasyPIC v7 Access 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

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 8 Click driver.

Key functions:

digipot8_write_data - DIGI POT 8 write data function
digipot8_set_wiper_1 - DIGI POT 8 set wiper 2 function
digipot8_set_wiper_2 - DIGI POT 8 set wiper 3 function

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 DIGIPOT8 Click example
 *
 * # Description
 * This example demonstrates the use of DIGI POT 8 Click board.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and makes an initial log.
 *
 * ## Application Task
 * Iterates through the entire wiper range and sets all wipers to 
 * the iterator value each second. 
 * The current wiper position will be displayed on USB UART.
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "digipot8.h"

static digipot8_t digipot8;
static log_t logger;

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    digipot8_cfg_t digipot8_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.

    digipot8_cfg_setup( &digipot8_cfg );
    DIGIPOT8_MAP_MIKROBUS( digipot8_cfg, MIKROBUS_1 );
    err_t init_flag  = digipot8_init( &digipot8, &digipot8_cfg );
    if ( init_flag == SPI_MASTER_ERROR ) 
    {
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );

        for ( ; ; );
    }

    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    for ( uint8_t cnt = DIGIPOT8_WIPER_POSITION_MIN; cnt < DIGIPOT8_WIPER_POSITION_MAX; cnt += 5 )
    {
        digipot8_set_wiper_1 ( &digipot8, cnt );
        digipot8_set_wiper_2 ( &digipot8, cnt );
        digipot8_set_wiper_3 ( &digipot8, cnt );
        digipot8_set_wiper_4 ( &digipot8, cnt );
        digipot8_set_wiper_5 ( &digipot8, cnt );
        digipot8_set_wiper_6 ( &digipot8, cnt );
        log_printf( &logger, " * All wipers position set to %d *\r\n", ( uint16_t ) cnt );
        
        Delay_ms( 1000 );
    }
}

void main ( void ) 
{
    application_init( );

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

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