Enjoy in high-resolution inductance-to-digital conversion thanks to the LDC1101 and PIC18F57Q43

Inductance meets digital

LDC1101 click with Curiosity Nano with PIC18F57Q43

Published Feb 13, 2024

Click board™

LDC1101 click

Dev. board

Curiosity Nano with PIC18F57Q43

Compiler

NECTO Studio

MCU

PIC18F57Q43

Our inductance-to-digital converter solution redefines precision sensing, offering unmatched accuracy and versatility for applications in industries like automotive, automation, and healthcare

Hardware Overview

How does it work?

LDC1101 Click is based on the LDC1101, an integrated high-resolution, high-speed inductance-to-digital converter from Texas Instruments. This IC is a versatile inductance converter used for fast, short-range, contactless position, rotation, or motion of an object. Due to the technology that allows precise and reliable inductivity sensing even in harsh environments, the LDC1101 is well-suited for industrial and automotive applications. The LDC1101 uses the standard SPI interface to be interfaced with the host MCU. Two sensing cores work independently. One core offers fast impedance and inductance (RP+L) readings with 16-bit resolution, while the other offers high-resolution 24-bit lessons of the inductance (LHR). While the RP+L can run without the input clock, the LHR mode requires a clock signal at the CLKIN pin. Therefore, the CLKIN pin is routed to the mikroBUS™ PWM pin. The LHR mode will not be available without the valid clock at this pin. The LDC 1101 offers two low-power modes: Shutdown mode and Sleep mode. In both modes, the IC does not actively run any conversions. While in the Shutdown mode, all the sections of the LDC1101 are turned off, so the least current is consumed. The logic section of the LDC1101 becomes active while in Sleep mode, and this mode is used to configure the working parameters. Configuring the IC is only valid when in Sleep mode. The Active mode uses the most

power as the entire IC becomes operational. The main working principle is based on measuring the parameters of the LC oscillator, formed by a PCB copper trace and a capacitor: when a conductive object approaches, it becomes magnetically coupled with the LC oscillator, driven by the LDC1101 IC. The LDC1101 then measures the energy it needs to provide to sustain the oscillation. The power loss of the oscillator circuit is proportional to the impedance of the conducting object, which is then sampled and becomes available as a digital value. Since the impedance value is affected by the object's distance, it can be used to determine its distance from the LC oscillator. Similarly, it is possible to determine its composition by having a fixed, known distance of the conductive object and by measuring the impedance (and inductance) parameters. The PCB copper trace becomes an impedance sensor in this case. The LHR mode is a better choice when more accurate inductance sensing is required. Unlike the impedance, the inductivity of a conductive object is not affected by its temperature that much. By utilizing the ability of the LDC1101 to measure the resonant frequency of the LC oscillator, it is also possible to accurately measure the distance of an object. The resonant frequency of the LC oscillator is affected by the conductive object, which becomes magnetically coupled with it. The resonant frequency of the LC oscillator

is a function of the inductance, so by measuring the change in the resonant frequency, it is possible to calculate the influence of the conductive object and, therefore, its distance very accurately. However, an accurate clock signal is required on the mikroBUS™ PWM pin to use the LHR mode. An integrated interrupt engine allows various events to be reported to the host MCU. For example, it is important to read the data before the result is corrupted by another conversion cycle. The interrupt can be triggered at the end of the conversion cycle for the RP+L mode and the LHR mode so that the MCU can fetch the data before the next conversion is started. The LDC1101 can also trigger an interrupt when a threshold is exceeded. If the conversion data is below or above the configured thresholds for both the inductance and the impedance parameters, an interrupt event will be triggered. Depending on the interrupt type, the INTB pin of the LDC1101 will be driven to a LOW logic level in case of an interrupt. This pin is multiplexed with the SDO pin, so there is a certain procedure to be followed when using this pin as the interrupt output: Besides configuring the SDO/INTB pin as the interrupt pin, an onboard SMD jumper needs to be switched to the appropriate position, routing the interrupt signal to the INT pin of the mikroBUS™.

Features overview

Development board

PIC18F57Q43 Curiosity Nano evaluation kit is a cutting-edge hardware platform designed to evaluate microcontrollers within the PIC18-Q43 family. Central to its design is the inclusion of the powerful PIC18F57Q43 microcontroller (MCU), offering advanced functionalities and robust performance. Key features of this evaluation kit include a yellow user LED and a responsive

mechanical user switch, providing seamless interaction and testing. The provision for a 32.768kHz crystal footprint ensures precision timing capabilities. With an onboard debugger boasting a green power and status LED, programming and debugging become intuitive and efficient. Further enhancing its utility is the Virtual serial port (CDC) and a debug GPIO channel (DGI

GPIO), offering extensive connectivity options. Powered via USB, this kit boasts an adjustable target voltage feature facilitated by the MIC5353 LDO regulator, ensuring stable operation with an output voltage ranging from 1.8V to 5.1V, with a maximum output current of 500mA, subject to ambient temperature and voltage constraints.

PIC18F57Q43 Curiosity Nano double side image

Microcontroller Overview

MCU Card / MCU

Architecture

PIC

MCU Memory (KB)

128

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

8196

You complete me!

Accessories

Curiosity Nano Base for Click boards is a versatile hardware extension platform created to streamline the integration between Curiosity Nano kits and extension boards, tailored explicitly for the mikroBUS™-standardized Click boards and Xplained Pro extension boards. This innovative base board (shield) offers seamless connectivity and expansion possibilities, simplifying experimentation and development. Key features include USB power compatibility from the Curiosity Nano kit, alongside an alternative external power input option for enhanced flexibility. The onboard Li-Ion/LiPo charger and management circuit ensure smooth operation for battery-powered applications, simplifying usage and management. Moreover, the base incorporates a fixed 3.3V PSU dedicated to target and mikroBUS™ power rails, alongside a fixed 5.0V boost converter catering to 5V power rails of mikroBUS™ sockets, providing stable power delivery for various connected devices.

Used MCU Pins

mikroBUS™ mapper

RST

SPI Chip Select

PD4

SPI Clock

PC6

SCK

SPI Data OUT

PC5

MISO

SPI Data IN

PC4

MOSI

Power supply

3.3V

Ground

GND

Time-Base Clock

PB0

PWM

Interrupt

PA6

INT

SCL

SDA

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

Curiosity Nano Base for Click boards front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Curiosity Nano with PIC18F57Q43 as your development board.

Barometer 13 Click front image hardware assembly

PIC18F57Q43 Curiosity Nano front image hardware assembly

Curiosity Nano with PICXXX MB 1 - upright/background hardware assembly

PIC18F57Q43 Curiosity MCU Step hardware assembly

Necto No Display image step 8 hardware assembly

Debug Image 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 LDC1101 Click driver.

Key functions:

ldc1101_get_rp_data - Functions for reads RP data
ldc1101_get_l_data - Functions for reads L data
ldc1101_get_interrupt - Functions for get interrupt pin status

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 Ldc1101 Click example
 * 
 * # Description
 * Example demonstrates measurement of inductance change depending on the linear motion of the metal object.
 * Induction of the linear metal position depends on the type of metal and the configuration.
 * 
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes I2C module and sets CS pin as OUTPUT and PWM and INT pin sa INPUT.
 * Driver intialization, standard configurations and start measurement.
 * 
 * ## Application Task  
 * Reads RP data and logs data to USBUART every 1 sec.
 * 
 * \author Nenad Filipovic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "ldc1101.h"

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

static ldc1101_t ldc1101;
static log_t logger;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    ldc1101_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.

    ldc1101_cfg_setup( &cfg );
    LDC1101_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    ldc1101_init( &ldc1101, &cfg );

    log_printf( &logger, "     LDC1101 Click\r\n" );
    log_printf( &logger, "------------------------\r\n" );
    
    ldc1101_default_cfg ( &ldc1101 );
    Delay_ms( 100 );
}

void application_task ( void )
{
    uint16_t rp_data;
    
    rp_data = ldc1101_get_rp_data( &ldc1101 );
    log_printf( &logger, " Inductive Linear Position : %u\r\n", rp_data );
    
    Delay_ms( 1000 );
}

void main ( void )
{
    application_init( );

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


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