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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();
         if (swp != wp) {
             swp = wp;
         lcd.printf("%f MHz", si570.get_frequency());



Import library

Public Member Functions

SI570 (PinName sda, PinName scl, int address)
Create an instance of the SI570 connected to specified I2C pins, with the specified address.
void si570reset (void)
Resets the SI570 .
double get_frequency (void)
Read the current frequency.
double get_rfreq (void)
Read the current rfreq value.
int get_n1 (void)
Read the current n1.
int get_hsdiv (void)
Read the current hsdiv.
int set_frequency (double frequency)
Set a new frequency.

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