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A simple PLL circuit with prescaler and ATtiny45 My good friend DL7CH asked me one day to build a Low Phase Noise and frequency-stable 1GHz oscillator for one of his RF projects. As such oscillators are a significant part for many HAM homemade projects, I decided to publish my design and my source code to make it easier for you to make your own PLL Oscillator :) I used a Crystek 1 GHz VCO, divided by 8 with a MC12093D and the PLL IC itself is a ADF4002. Quite simple, quite effective, quite cheap. The output signal is coupled by a MiniCircuits 17dB coupler DBTC-17-5 (U106 in the schematic). To amplify the decoupled signal I used a cheap and small BGA614.
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Find the source code below:
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/* * ===================================================================================== * * Filename: pll.c * * Description: ADF4002 mit 1GHz Crystek und 10MHz Ref, ATtiny45 * * Version: 1.0 * Created: 17.12.2019 21:17:36 * Revision: none * Compiler: gcc * * Author: Andre Schoch (), contact@dl4uny.de * Organization: DL4UNY * * ===================================================================================== */ /********************************************************* USI to SPI communication routine Controller: ATtiny 45, Osc. = 1 MHz *********************************************************/ #define F_CPU 1000000UL #include <avr/io.h> #include <stdlib.h> #include <util/delay.h> #define LED PB3 #define USCK PB2 //CLK #define DO PB1 //Data Out #define DI PB0 //Data In #define LE PB4 //Latch Enable void SPI_init(void) { DDRB |= (1<<USCK)|(1<<DO); //Output: PB2=USCK, PB1=DO DDRB &= ~(1<<DI); //Input: PB0=DI PORTB |= (1<<DI); //int. Pull-up an PB0 aktivieren DDRB |= (1<<LED); //LED auf Ausgang USICR = (1<<USIWM0) | (1<<USICLK)|(1<<USITC)| (1<<USICS1); // USIWM0 = 1: SPI-Betrieb mit DO, DI und USCK // USICLK = 1, USITC = 1, USICS1 = 1: generiert den Taktimpuls für das Schieberegister und // den 4bit Timer. Der Takt wird am USCK-Pin (PA4) ausgegeben. } void SPI_transfer(int data) { USIDR = data; //Daten in Data Register laden USISR |= (1<<USIOIF); //Überlaufflag löschen while (!(USISR & (1<<USIOIF))) //solange kein Timerüberlauf... { USICR |= (1<<USITC); //Toggle clk (2x) USICR |= (1<<USITC); } } void pll(void) { //ADF4002 //initialization latch uint8_t I_LATCH_H = 0b00011011; //X X PD2 CPI6 CPI5 CPI4 CPI3 CPI2 uint8_t I_LATCH_M = 0b01110000; //CPI1 TC4 TC3 TC2 TC1 F5 F4 F3 uint8_t I_LATCH_L = 0b00000011; //F2 M3 M2 M1 PD1 F1 C2 C1 //function latch uint8_t F_LATCH_H = 0b00011011; //X X PD2 CPI6 CPI5 CPI4 CPI3 CPI2 uint8_t F_LATCH_M = 0b01110000; //CPI1 TC4 TC3 TC2 TC1 F5 F4 F3 uint8_t F_LATCH_L = 0b00000010; //F2 M3 M2 M1 PD1 F1 C2 C1 //main counter uint8_t N_COUNTER_H = 0b00100000; //X X G1 B13 B12 B11 B10 B9 uint8_t N_COUNTER_M = 0b01111101; //B8 B7 B6 B5 B4 B3 B2 B1 uint8_t N_COUNTER_L = 0b00000001; //X X X X X X C2 C1 //reference counter uint8_t R_COUNTER_H = 0b00010011; //X 0 0 LDP T2 T1 ABP2 ABP1 uint8_t R_COUNTER_M = 0b00000000; //R14 R13 R12 R11 R10 R9 R8 R7 uint8_t R_COUNTER_L = 0b00101000; //R6 R5 R4 R3 R2 R1 C2 C1 PORTB &= ~(1<<LE); //LE auf Low SPI_transfer(I_LATCH_H); SPI_transfer(I_LATCH_M); SPI_transfer(I_LATCH_L); PORTB |= (1<<PB0); //LE auf High _delay_us(1); PORTB &= ~(1<<LE); //LE auf Low SPI_transfer(F_LATCH_H); SPI_transfer(F_LATCH_M); SPI_transfer(F_LATCH_L); PORTB |= (1<<LE); //LE auf High _delay_us(1); PORTB &= ~(1<<LE); //LE auf Low SPI_transfer(R_COUNTER_H); SPI_transfer(R_COUNTER_M); SPI_transfer(R_COUNTER_L); PORTB |= (1<<LE); //LE auf High _delay_us(1); PORTB &= ~(1<<LE); //LE auf Low SPI_transfer(N_COUNTER_H); SPI_transfer(N_COUNTER_M); SPI_transfer(N_COUNTER_L); PORTB |= (1<<LE); //LE auf High _delay_ms(1); } void blink(void) { PORTB &= !(1<<LED); // LED on _delay_ms(100); PORTB |= (1<<LED); // LED off _delay_ms(100); } int main(void) { blink(); SPI_init(); blink(); pll(); _delay_ms(10); pll(); blink(); _delay_ms(500); blink(); /* while(1) { pll(); PORTB |= (1<<LED); // Led on _delay_ms(100); PORTB &= !(1<<LED); // Led off _delay_ms(100); } */ } |