Enjoy in high-resolution inductance-to-digital conversion thanks to the LDC1101 and PIC18F2455

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™.

Curiosity HPC, standing for Curiosity High Pin Count (HPC) development board, supports 28- and 40-pin 8-bit PIC MCUs specially designed by Microchip for the needs of rapid development of embedded applications. This board has two unique PDIP sockets, surrounded by dual-row expansion headers, allowing connectivity to all pins on the populated PIC MCUs. It also contains a powerful onboard PICkit™ (PKOB), eliminating the need for an external programming/debugging tool, two mikroBUS™ sockets for Click board™ connectivity, a USB connector, a set of indicator LEDs, push button switches and a variable potentiometer. All

these features allow you to combine the strength of Microchip and Mikroe and create custom electronic solutions more efficiently than ever. Each part of the Curiosity HPC development board contains the components necessary for the most efficient operation of the same board. An integrated onboard PICkit™ (PKOB) allows low-voltage programming and in-circuit debugging for all supported devices. When used with the MPLAB® X Integrated Development Environment (IDE, version 3.0 or higher) or MPLAB® Xpress IDE, in-circuit debugging allows users to run, modify, and troubleshoot their custom software and hardware

quickly without the need for additional debugging tools. Besides, it includes a clean and regulated power supply block for the development board via the USB Micro-B connector, alongside all communication methods that mikroBUS™ itself supports. Curiosity HPC development board allows you to create a new application in just a few steps. Natively supported by Microchip software tools, it covers many aspects of prototyping thanks to many number of different Click boards™ (over a thousand boards), the number of which is growing daily.