回路図
si5351a Xtal代替発振器の回路図通り。ボリューム変化量
10BitのADCの為、0-1023の値を持つ。この為、発振周波数＋1023 が目標周波数でであれば簡単だが、VXOとして使える範囲が限定される。そこで、水晶発振子を使ったVXOと同等な性能を目指す事にした。目標可変範囲を±30kHzとした。これをADC分解能で現すと±30倍スケーリングしなければならない。1Bitの変化が30Hzとして計算されるので、ADCによる変換誤差、外来ノイズなど顕著に周波数に反映された結果、周波数が揺らぐ。この揺らぎは、5倍のスケーリングした時でも受信機にトーン変化として感じられた。使い勝手と揺らぎ有無判断から、ADC値2倍のスケーリング（分解能 ２Hz）を行うことにした。従って、ADC＊2（0-2046）がボリューム変化量となる。周波数中心値
ADC値を2倍した値をボリュームの最小位置から最大位置として使うので、ボリューム中心値を発振周波数（初期値）と操作性が良い。そこでオフセット 発振周波数ー1023 にした。可変範囲拡張方法
今迄の説明で、発振周波数±1023 即ち、発振周波数±1kHz変化する事が想像出来た思うが、30kHz程安定して可変させるには工夫がいる。SSB運用形態を観ていると、1kHzステップ刻みが多い。そこで1kHzスキップさせる為、SKIP SWを付けた。SKIPを押すと、+1kHzまたは-1kHzスキップさせる事にした。+またはー判断は、ボリュームの中心値を基準に大小判断にした。SKIPを押す度にEEPROMに周波数を保存して可変範囲を拡張した。このVXOを仮称「GQP VXO」と呼ぶ。EEPROM初期化の方法
表示器を持たないシステムの場合、初期化は重要である。SKIP SWを押しながら電源スイッチを投入すると、EEPROMが初期化される方式にした。(初めて使う時は、初期化が必要）スケッチ
Mplab X X8Cを使って開発を行った。スケッチはJA2GQP's Download siteのPICフォルダからダウンロード可能。////////////////////////////////////////////////////////////
// si5351a PLL control(PIC12F1840)
//
// 2018/09/03
// JA2GQP
////////////////////////////////////////////////////////////
//---------- Header file include -------------------------//
#include <xc.h>
//----------Configuration setting ------------------------//
////////////////////////////
// config1
////////////////////////////
#pragma config FOSC = INTOSC // Internal clock
#pragma config WDTE = OFF // Watchdog timer off
#pragma config PWRTE = ON // Power on start
#pragma config MCLRE = OFF // External reset not used
#pragma config CP = OFF // Program memory not protected
#pragma config CPD = OFF // Data memory not protected
#pragma config BOREN = ON // Power drop monitoring
#pragma config CLKOUTEN = OFF // Clock out pin is RA4
#pragma config IESO = OFF // No activation with clock switching
#pragma config FCMEN = OFF // Do not monitor external clock
////////////////////////////
// config2
////////////////////////////
#pragma config WRT = OFF // Flash memory not protected
#pragma config PLLEN = OFF // It does not work at 32 MHz
#pragma config STVREN = ON // Reset with stack overflow(underflow)
#pragma config BORV = HI // Voltage drop monitoring
#pragma config LVP = OFF // Low voltage programming not used
//---------- Define value setting ------------------------//
#define DEF_FREQ 14000000-AD_OFFSET // Default frequency
#define EEP_ADR 0x00 // EEPROM address
#define SCL RA1 // I2C Clock
#define SDA RA2 // I2C Data
#define AD_OFFSET 1023 // Frequency offset
#define _XTAL_FREQ 16000000 // clock 16MHz(Use with delay)
////////////////////////////
// si5351a parameter
////////////////////////////
#define CLK0_CTRL 16 // Register definitions
#define CLK1_CTRL 17
#define MSNA_ADDR 26
#define MS0_ADDR 42
#define PLL_RESET 177
#define XTAL_LOAD_C 183
#define R_DIV_1 0b00000000 // R-division ratio definitions
#define Si5351A_ADDR 0xC0 // address(cip address<<1)
#define XTAL_FREQ 25000000 // Crystal frequency for Hans' board
#define _6pF 0b01010010 // 6pF
#define _8pF 0b10010010 // 8pF
#define _10pF 0b11010010 // 10pF
#define XTAL_CL _8pF // XTAL_CL 8pF set
#define _2mA 0x4C // 2mA(1dBm))
#define _4mA 0x4D // 4mA(5dBm))
#define _6mA 0x4E // 6mA(10dBm))
#define _8mA 0x4F // 8mA(12dBm)
#define mA _6mA // output lebel 10dBm set
//---------- Memory define -------------------------------//
static unsigned long frequency=DEF_FREQ; // Frequency data
//------------- Initial proc. ----------------------------//
void PIC12F1840_set(){
OSCCON = 0b01111000 ; // clock set(16MHz=0x78,8MHz=0x70,4MHz=0x68)
ANSELA = 0b00010000 ; // Anarog = AN3,Othe digital
TRISA = 0b00011000; // I/O set(0=output,1=input)
PORTA = 0b00000000 ; // Output pin initial value
EECON1bits.CFGS =0; // EEPROM
EECON1bits.EEPGD = 0;
ADCON1 = 0b11010000 ; // FOSC/16,VDD=Ref
ADCON0 = 0b00001101 ;
__delay_us(5) ; // 5us(at clock 16MHz))
}
//------------- wait proc. -------------------------------//
void await(unsigned long ct){
while(ct>0) ct--;
}
//------------- I2C start proc. --------------------------//
void I2C_start(){
SCL = 1; // start condition
await(3);
SDA = 1;
await(3);
SDA = 0;
await(3);
SCL = 0;
await(3);
}
//------------- I2C stop proc. ---------------------------//
void I2C_stop(){
await(3);
SCL = 1; // stop condition
await(3);
SDA = 0;
await(3);
SDA = 1;
await(3);
SCL = 0;
await(3);
}
//------------- I2C write byte proc. ---------------------//
void wr_Byte(unsigned char x){
unsigned int k;
for(k=0;k<8;k++){
if(x & 0x80) SDA = 1; else SDA = 0;
await(3);
SCL = 1;
await(3);
SCL = 0;
await(3);
SDA = 0;
x <<= 1;
}
SCL = 1;
await(3);
SCL = 0;
}
//------------- si5351 command processing ----------------//
void Si5351_write(unsigned char reg_No, unsigned char x){
I2C_start();
wr_Byte(Si5351A_ADDR); // address set
wr_Byte(reg_No);
wr_Byte(x);
I2C_stop();
}
//------------- si5351 Initialization --------------------//
void Si5351_init(void){
SDA=1;
SCL=1;
await(200);
Si5351_write(XTAL_LOAD_C,XTAL_CL); // XTAL_CL set
Si5351_write(CLK0_CTRL,0x80); // Disable CLK0
Si5351_write(PLL_RESET,0xA0); // Reset PLL_A
Si5351_write(CLK0_CTRL,mA);
}
//------------- si5351 PLL data set --------------------------//
void setupPLL(unsigned char pll, unsigned char mult, unsigned long num, unsigned long denom){
unsigned long P1; // PLL config register P1
unsigned long P2; // PLL config register P2
unsigned long P3; // PLL config register P3
P1 = (unsigned long)(128 * ((float)num / (float)denom));
P1 = (unsigned long)(128 * (unsigned long)(mult) + P1 - 512);
P2 = (unsigned long)(128 * ((float)num / (float)denom));
P2 = (unsigned long)(128 * num - denom * P2);
P3 = denom;
Si5351_write(pll + 0, (P3 & 0x0000FF00) >> 8);
Si5351_write(pll + 1, (P3 & 0x000000FF));
Si5351_write(pll + 2, (P1 & 0x00030000) >> 16);
Si5351_write(pll + 3, (P1 & 0x0000FF00) >> 8);
Si5351_write(pll + 4, (P1 & 0x000000FF));
Si5351_write(pll + 5, ((P3 & 0x000F0000) >> 12) | ((P2 & 0x000F0000) >> 16));
Si5351_write(pll + 6, (P2 & 0x0000FF00) >> 8);
Si5351_write(pll + 7, (P2 & 0x000000FF));
}
//------------- Set up MultiSynth --------------------------//
void setupMultisynth(unsigned char synth, unsigned long divider, unsigned char rDiv){
unsigned long P1; // Synth config register P1
unsigned long P2; // Synth config register P2
unsigned long P3; // Synth config register P3
P1 = 128 * divider - 512;
P2 = 0; // P2 = 0, P3 = 1 forces an integer value for the divider
P3 = 1;
Si5351_write(synth + 0, (P3 & 0x0000FF00) >> 8);
Si5351_write(synth + 1, (P3 & 0x000000FF));
Si5351_write(synth + 2, ((P1 & 0x00030000) >> 16) | rDiv);
Si5351_write(synth + 3, (P1 & 0x0000FF00) >> 8);
Si5351_write(synth + 4, (P1 & 0x000000FF));
Si5351_write(synth + 5, ((P3 & 0x000F0000) >> 12) | ((P2 & 0x000F0000) >> 16));
Si5351_write(synth + 6, (P2 & 0x0000FF00) >> 8);
Si5351_write(synth + 7, (P2 & 0x000000FF));
}
//------------- si5351 data set --------------------------//
void si5351aSetFrequency(unsigned long frequency){
unsigned long pllFreq;
unsigned long xtalFreq = XTAL_FREQ;
unsigned long l;
float f;
unsigned char mult;
unsigned long num;
unsigned long denom;
unsigned long divider;
divider = 900000000 / frequency; // Calculate the division ratio. 900,000,000 is the maximum internal
// PLL frequency: 900MHz
if (divider % 2) divider--; // Ensure an even integer
//division ratio
pllFreq = divider * frequency; // Calculate the pllFrequency:
//the divider * desired output frequency
mult = pllFreq / xtalFreq; // Determine the multiplier to
//get to the required pllFrequency
l = pllFreq % xtalFreq; // It has three parts:
f = l; // mult is an integer that must be in the range 15..90
f *= 1048575; // num and denom are the fractional parts, the numerator and denominator
f /= xtalFreq; // each is 20 bits (range 0..1048575)
num = f; // the actual multiplier is mult + num / denom
denom = 1048575; // For simplicity we set the denominator to the maximum 1048575
// Set up PLL A with the calculated multiplication ratio
setupPLL(MSNA_ADDR, mult, num, denom);
// Set up MultiSynth divider 0, with the calculated divider.
// The final R division stage can divide by a power of two, from 1..128.
// reprented by constants SI_R_DIV1 to SI_R_DIV128 (see si5351a.h header file)
// If you want to output frequencies below 1MHz, you have to use the
// final R division stage
setupMultisynth(MS0_ADDR, divider, R_DIV_1);
}
//------------- ADconverter ------------------------------//
unsigned int adconv(){
unsigned int temp;
GO_nDONE = 1 ; // Anarog read start
while(GO_nDONE) ; // PIC wait
temp = ADRESH ; // Data high set
temp = ( temp << 8 ) | ADRESL ; // low set
return temp * 2 ; // (0-1023) * 2 = 0-2046
}
//------------- EEPROM read ------------------------------//
unsigned long eep_rd(unsigned char address){
unsigned long temp = 0;
temp = eeprom_read(address+3);
temp = temp << 8;
temp = temp | eeprom_read(address+2);
temp = temp << 8;
temp = temp | eeprom_read(address+1);
temp = temp << 8;
temp = temp | eeprom_read(address+0);
return temp;
}
//------------- EEPROM write -----------------------------//
void eep_wt(unsigned char address,unsigned long frequency){
eeprom_write(address+0,(frequency & 0xff));
eeprom_write(address+1,((frequency >> 8) & 0xff));
eeprom_write(address+2,((frequency >> 16) & 0xff));
eeprom_write(address+3,((frequency >> 24) & 0xff));
}
//------------- EEPROM initialize -----------------------------//
void eep_init(){
if(RA3 == 0){
while(RA3 == 0)
;
eep_wt(EEP_ADR,frequency);
eeprom_write(0x0f,0x49);
}
if(eeprom_read(0x0f) == 0x49)
frequency = eep_rd(EEP_ADR);
}
//------------- main -------------------------------------//
void main(){
int wk,wk1,i;
char skip;
eep_init();
PIC12F1840_set(); // Cip Initialization
Si5351_init(); // si5351a Initialization
while(1){
wk = adconv();
if(RA3 == 0){
if(wk < 1024)
frequency = frequency - 1000;
else
frequency = frequency + 1000;
eep_wt(EEP_ADR,frequency);
si5351aSetFrequency(frequency + wk); // Frequency data set
while(RA3 == 0)
;
}
else{
if(wk != wk1){
si5351aSetFrequency(frequency + wk); // Frequency data set
wk1 = wk;
}
}
__delay_ms(30);
}
}
