Interaktive Kalibration eines Si5351 Chips. Es ist eine Auflösung auf 1 Herz möglich. DieLangzeitkonstanz ist eine andere Frage, ebenso der Einsatz eins TXCO mit wenig Frequenzsprüngen (siehe Jason’s Webseite).

 

/* Simple calibration routine for the Si5351 breakout board.
*
* Copyright 2015 Paul Warren <pwarren@pwarren.id.au>
*
* Uses code from https://github.com/darksidelemm/open_radio_miniconf_2015
* and the old version of the calibration sketch
*
* This sketch  is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* Foobar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License.
* If not, see <http://www.gnu.org/licenses/>.
*/

#include "si5351.h"
#include "Wire.h"

Si5351 si5351;

int32_t cal_factor;
int32_t old_cal;

uint64_t rx_freq;
uint64_t target_freq = 1000000000ULL; // 10 MHz, in hundredths of hertz

void setup()
{
  // Start serial and initialize the Si5351
  Serial.begin(57600);
  si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0);

  // get old cal factor
  //old_cal = si5351.get_correction();  
  si5351.set_correction(0);
  // start on target frequency
  si5351.set_pll(SI5351_PLL_FIXED, SI5351_PLLA);
  si5351.set_freq(target_freq, SI5351_PLL_FIXED, SI5351_CLK0);
  si5351.output_enable(SI5351_CLK1, 0);
  si5351.output_enable(SI5351_CLK0, 1);
}

void loop()
{
  si5351.update_status();
  if (si5351.dev_status.SYS_INIT == 1) {
     Serial.println("Initialising Si5351, you shouldn't see many of these!");
     delay(500);
  } else {
    cal_factor = 0;
//    Serial.print("Old cal factor was: ");
//    Serial.println(old_cal);
//    Serial.println("Cal factor now set to 0");
//    si5351.set_correction(0);
    Serial.println();
    Serial.println(F("Adjust until your frequency counter reads as close to 10 MHz as possible"));
    vfo_interface();
    Serial.print(F("Calibration factor is "));
    Serial.println(cal_factor);
    Serial.println("Setting calibration factor");
    si5351.set_correction(cal_factor);
    Serial.println("Resetting target frequency");
    si5351.set_freq(target_freq, SI5351_PLL_FIXED, SI5351_CLK0);
  }  
  
  
}

static void flush_input(void)
{
  while (Serial.available() > 0)
  Serial.read();
}

static void vfo_interface(void)
{
  rx_freq = target_freq;
  Serial.println(F("   Up:   r   t  y  u  i   o  p"));
  Serial.println(F(" Down:   f   g  h  j  k   l  ;"));
  Serial.println(F("   Hz: 0.01 0.1 1 10 100 1K 10k"));
  while (1) {
  if (Serial.available() > 0) {
    char c = Serial.read();
    switch (c) {
      case 'q':
        flush_input();
        return;
      case 'r': rx_freq += 1; break;
      case 'f': rx_freq -= 1; break;
      case 't': rx_freq += 10; break;
      case 'g': rx_freq -= 10; break;
      case 'y': rx_freq += 100; break;
      case 'h': rx_freq -= 100; break;
      case 'u': rx_freq += 1000; break;
      case 'j': rx_freq -= 1000; break;
      case 'i': rx_freq += 10000; break;
      case 'k': rx_freq -= 10000; break;
      case 'o': rx_freq += 100000; break;
      case 'l': rx_freq -= 100000; break;
      case 'p': rx_freq += 1000000; break;
      case ';': rx_freq -= 1000000; break;
      default:
        // Do nothing
      continue;
    }
    si5351.set_freq(rx_freq,SI5351_PLL_FIXED,SI5351_CLK0);
    cal_factor = (int32_t)(target_freq - rx_freq);
    Serial.print("Current difference:");
    Serial.println(cal_factor);
    }
  }
}