This is the page for the Silicon Laboratories Si570 frequency synthesizer, with I2C interface.¶

The Si570 XO/Si571 VCXO utilizes Silicon Laboratories’ advanced DSPLL® circuitry to provide a low-jitter clock at any frequency. The Si570/Si571 are user-programmable to any output frequency from 10 to 945 MHz and select frequencies to 1400 MHz with <1 ppb resolution. The device is programmed via an I2C serial interface. Unlike traditional XO/VCXOs where a different crystal is required for each output frequency, the Si57x uses one fixed- frequency crystal and a DSPLL clock synthesis IC to provide any-frequency operation. This IC-based approach allows the crystal resonator to provide exceptional frequency stability and reliability. In addition, DSPLL clock synthesis provides superior supply noise rejection, simplifying the task of generating low-jitter clocks in noisy environments typically found in communication systems.

The Si570 is very popular for amateur radio use. It can be used as the local oscillator in a superheterodyne receiver, or it can be the local oscillator in a direct conversion quadrature receiver for software defined radio (SDR) such as the Softrock. In addition to its use inside a receiver, the Si570 kit can be used as a stand-alone signal source for test and measurement and for other purposes, such as a VFO for your old Heathkit DX40 for that matter. Just keep in mind that the Si570's output is a square wave and may require additional filtering for some purposes.

Hello World!¶

 #include "mbed.h"
 #include "TextLCD.h"
 #include "SI570.h"
 #include "QEI.h"
 
 TextLCD lcd(p11, p12, p15, p16, p29, p30); // rs, e, d0-d3
 SI570 si570(p9, p10, 0xAA);
 QEI wheel (p5, p6, NC, 360);
 
 int main() {
     int wp,swp=0;
     float startfreq=7.0;
     float freq;
 
     while (1) {
         wp =  wheel.getPulses();
         freq=startfreq+wp*0.00001;
         if (swp != wp) {
             si570.set_frequency(freq);
             swp = wp;
         }                
         lcd.locate(0,0);
         lcd.printf("%f MHz", si570.get_frequency());
     }
 }

Links¶

• NXP mbed design challenge entry: Si570-Based Universal HAM Radio VFO
• www.agri-vision.nl (home of this project)
• Experiments with software defined radio (SDR) using Softrock, the Si570 VCXO, and a hacked Linux based ADM5120 router to control the Si570, using a web browser.
• Review of Si570 Frequency Synthesizer Kit from K5JHF and K5BCQ
• DG8SAQ - Si570 control with AVR

Reference¶

• Si570 Datasheet
• Aplication note AN334