30 min

Track time with laser precision using AS6500 and MK64FX512VDC12

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TDC 2 Click with Fusion for ARM v8

Published May 27, 2023

Click board™

TDC 2 Click

Development board

Fusion for ARM v8


NECTO Studio



Unleash the boundless possibilities of this high-performance time-to-digital converter today



Hardware Overview

How does it work?

TDC 2 Click is based on the AS6500, a high-resolution time-to-digital converter from ScioSense, featuring CMOS inputs, high measurement performance, and high data throughput. The AS6500 can measure time intervals as low as 5ns with 10ps resolution on all four STOP channels at a sampling rate of up to 1.5Ms/s. It is characterized by high configuration flexibility, a wide measurement range from 0 to 16s, and simple data post-processing thanks to calibrated results. It calculates calibrated stop measurements referenced to the applied reference clock. This Click board™ is ideal for optical applications, including general-purpose laser distance measurement in 1D, 2D, and 3D, speed control, object recognition, time-of-flight spectroscopy, and many more. The positive edges of the stop signals, applied on the STOP terminals (1-4), are measured versus the preceding reference clock edge. The reference clock can be brought externally via the CLR

pin on the middle header terminal or from the onboard 8MHz quartz oscillator. This feature is selectable through software – register-setting. The reference clock represents the framework for all time measurements and serves as a universal time base. The TDC measures the clock pulses continuously as a time reference point for STOP pulses and an internal reference period. The measurement of the STOP events always refers to the preceding reference clock. The reference clock is counted continuously, and the actual count is assigned as a reference index to a STOP pulse. TDC 2 Click communicates with the host MCU through a standard SPI interface to read data and configure the frontend, supporting high clock speed up to 50MHz and the most common SPI mode, SPI Mode 1. SPI pins also use an interrupt pin that indicates to the host MCU that data are available and ready for processing. The AS6500 uses several more signals available on the

mikroBUS™ socket for successful time measurements. With the RIR pin, the internal counter for the reference index is set back to zero, simplifying the overview of the reference index in the output data stream. Next, setting the disable pin, marked as DIS, to a high logic state, the measurements on all four stops are disabled. On the other hand, the reference clock is not affected, and internal reference measurements are continued. Apart from the mikroBUS™ socket, these signals can also be found on the middle header, grouped with the reference clock pin. This Click board™ can only be operated with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used as a reference for further development.

TDC 2 Click hardware overview image

Features overview

Development board

Fusion for ARM v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different ARM® Cortex®-M based MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. 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, Fusion for ARM v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the Fusion for ARM v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it 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 HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. Fusion for ARM 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.

Fusion for ARM v8 horizontal image

Microcontroller Overview

MCU Card / MCU



8th Generation


ARM Cortex-M4

MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Reference Index Reset
SPI Chip Select
SPI Clock
Power Supply
STOP Disable

Take a closer look


TDC 2 Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Fusion for ARM v8 as your development board.

Fusion for PIC v8 front image hardware assembly
GNSS2 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
v8 SiBRAIN Access MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
NECTO Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image 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.

UART Application Output Step 1

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.

UART Application Output Step 2

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".

UART Application Output Step 3

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.

UART Application Output Step 4

Software Support

Library Description

This library contains API for TDC 2 Click driver.

Key functions:

  • tdc2_read_results TDC 2 results data reading function.

  • tdc2_start_measuring TDC 2 start measuring function.

  • tdc2_set_resolution TDC 2 set resolution 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 TDC 2 Click example
 * # Description
 * This library contains API for TDC 2 Click driver. 
 * The library initializes and defines the SPI bus drivers to 
 * write and read data from registers, as well as the default 
 * configuration for a reading time between two STOP signals.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver after that resets the device and 
 * performs default configuration and sets the device in read mode.

 * ## Application Task
 * This example demonstrates the use of the TDC 2 Click board by 
 * measuring the time between two STOP signals. This example is set up to
 * generate stop signals until FIFO fil's up which is indicated by interrupt pin going to low state.
 * After that FIFO buffer is completely emptied by reading, and that data is used to calculate 
 * the time between STOP signals.
 * @note
 * In order to test this example, you will need to connect STOP1 with the DIS pin. Disable pin is 
 * disabled by software and it isn't going to affect the working state of the TDC 2 Click Bord.
 * @author Stefan Ilic

#include "board.h"
#include "log.h"
#include "tdc2.h"

static tdc2_t tdc2;
static log_t logger;

 * @brief Dev generate stop signal function.
 * @details This function generates the stop signal by toggling DIS pin.
 * @param[out] cfg : Click configuration structure.
 * See #tdc2_cfg_t object definition for detailed explanation.
 * @return Nothing.
 * @note DIS pin ( Disable STOP channels) is disabled by software and isn't affecting the example.
void dev_generate_stop( tdc2_t *ctx );

void application_init ( void )
    log_cfg_t log_cfg;  /**< Logger config object. */
    tdc2_cfg_t tdc2_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.
    tdc2_cfg_setup( &tdc2_cfg );
    TDC2_MAP_MIKROBUS( tdc2_cfg, MIKROBUS_1 );
    if ( SPI_MASTER_ERROR == tdc2_init( &tdc2, &tdc2_cfg ) )
        log_error( &logger, " Communication init." );
        for ( ; ; );
    if ( TDC2_ERROR == tdc2_default_cfg ( &tdc2 ) )
        log_error( &logger, " Default configuration." );
        for ( ; ; );
    tdc2_start_measuring ( &tdc2 );
    log_info( &logger, " Application Task " );

void application_task ( void )
    uint32_t reference_index [ 18 ] = { 0 };
    uint32_t stop_result [ 18 ] = { 0 };
    uint8_t cnt = 0;
    tdc2_reset_index( &tdc2 );
    Delay_ms( 10 );
    while ( tdc2_get_int_state( &tdc2 ) == 1 )
        dev_generate_stop( &tdc2 );
        Delay_ms( 100 );
    while ( tdc2_get_int_state( &tdc2 ) == 0 )
        tdc2_read_results( &tdc2, TDC2_REG_INDEX_CH1_BYTE3, &reference_index[ cnt ], &stop_result[ cnt ] );
        log_printf( &logger, "CH1: Reference Index[%d]: %lu, Stop Result[%d]: %lu \r\n", ( uint16_t ) cnt, 
                    reference_index[ cnt ], ( uint16_t ) cnt, stop_result[ cnt ] ); 
        Delay_ms( 10 ); 
        if ( cnt )
            uint32_t time = 0;
            tdc2_get_time_between_stops ( &tdc2, stop_result[ cnt - 1 ], reference_index[ cnt - 1 ],
                                          stop_result[ cnt ], reference_index[ cnt ], &time );
            log_printf( &logger, "Time between STOP %d and STOP %d is %lu ms \r\n", 
                        ( uint16_t ) ( cnt - 1 ), ( uint16_t ) cnt, time / TDC2_uS_TO_mS ); 
            Delay_ms( 10 );
    log_printf( &logger, "---------------------------------------------- \r\n" ); 

void main ( void )
    application_init( );

    for ( ; ; )
        application_task( );

void dev_generate_stop( tdc2_t *ctx )
    digital_out_high( &ctx->dis );
    Delay_ms( 1 );
    digital_out_low( &ctx->dis );

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

Additional Support