Generate high-frequency clock output with ICS501 and ATmega644

Phase-Locked Loop (PLL) mechanism

Published Aug 09, 2023

Click board™

PLL Click

Dev. board

EasyAVR v7

Compiler

NECTO Studio

MCU

ATmega644

Generate highly stable and coherent high-frequency signals for applications requiring tight synchronization and minimal phase noise

Hardware Overview

How does it work?

PLL Click is based on the ICS501, a LOCO™ PLL clock multiplier, from Integrated Device Technology. This IC uses the Phase-Locked Loop to provide a high-frequency clock output, deriving input from a much cheaper, standard fundamental frequency crystal oscillator. Besides the onboard crystal oscillator fixed at 12MHz, it is possible to select the signal from the mikroBUS™ PWM pin as the clock input source. To select the desired multiplication factor, the states of the two input pins, S0 and S1, are routed to the mikroBUS™ pins RST and AN, respectively. These pins can be set to a HIGH or LOW logic state or disconnected (by tri-stating the MCU pins). The combination of these pins states will set the PLL

Click to a specific multiplier. The Output Enable (OE) pin of the ICS501 is used to turn off the output clock by setting it to a LOW logic level. It will additionally set the clock output pin in high impedance (Hi-Z) mode, allowing complete disconnection and no influence on the rest of the circuit, which is useful for experimenting and prototyping purposes. This pin is internally pulled to a HIGH logic level. The OE pin is routed to the CS pin of the mikroBUS™. PLL Click is equipped with two onboard SMD jumpers. The SMD jumper labeled as the VCC SEL is used to select the operating voltage level, consequently limiting the amplitude of the clock output signal with respect to the selected voltage. The other SMD jumper

labeled as the OSC SEL chooses the clock input source between the onboard 12MHz crystal oscillator or the external clock signal. The output signal is routed through the onboard SMA connector, which provides a secure connection and good signal shielding. PLL Click has a library containing functions for all the MIKROE compilers (mikroBASIC, mikroPASCAL, and mikroC). Although relatively easy to control, the library offers comprehensive functions that make the code readable and easy to use. The included example application demonstrates the use of these functions, and it can be used as a reference for custom projects.

Features overview

Development board

EasyAVR v7 is the seventh generation of AVR development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 16-bit AVR microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB. 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, EasyAVR v7 allows you to connect accessory boards, sensors, and custom electronics more

efficiently than ever. Each part of the EasyAVR 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 a wide range of external power sources, including an external 12V power supply, 7-12V AC or 9-15V 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 which cover a wide range of 16-bit AVR MCUs. EasyAVR 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

AVR

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

4096

Used MCU Pins

mikroBUS™ mapper

Multiplier Adjustment

PA7

Multiplier Adjustment

PA6

RST

Output Enable

PA5

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

External Clock Source

PD4

PWM

INT

SCL

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

EasyAVR v7 front image hardware assembly

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

EasyAVR v7 Access DIP 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

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 PLL Click driver.

Key functions:

pll_set_clock_output - This function settings clock output
pll_set_pll_4x - This function settings PLL x4
pll_set_pll_6x - This function settings PLL x6

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 PLL Click example
 * 
 * # Description
 * This app sets PLL signals.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes device.
 * 
 * ## Application Task  
 * Every 2 seconds, the PLL increases the input clock from min (x2) to max (x8) level.
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "pll.h"

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

static pll_t pll;
static log_t logger;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    pll_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.
    pll_cfg_setup( &cfg );
    PLL_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    pll_init( &pll, &cfg );
    pll_set_clock_output( &pll, PLL_CLOCK_ENABLE );
}

void application_task ( void )
{
    log_printf( &logger, " PLL level: x2\r\n\n" );
    pll_set_pll_2x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x3\r\n\n" );
    pll_set_pll_3x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x3.125\r\n\n" );
    pll_set_pll_3_125x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x4\r\n\n" );
    pll_set_pll_4x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x5\r\n\n" );
    pll_set_pll_5x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x5.3125\r\n\n" );
    pll_set_pll_5_3125x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x6\r\n\n" );
    pll_set_pll_6x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x6.25\r\n\n" );
    pll_set_pll_6_25x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
    log_printf( &logger, " PLL level: x8\r\n\n" );
    pll_set_pll_8x( &pll );
    Delay_ms ( 1000 );
    Delay_ms ( 1000 );
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}

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