25 Mhz Init not working

[AtariAndre]

Hi Pavel,

I found this library and it seems just what I need. I am using a "China" Attinny85 board with an original Adafruit SI5351 breakout board.

I tried a simple program to run 1 clock (0) at 16 Mhz. However when I measure I get an output of 14.8 Mhz instead. I think the Si.init(25000000); command seems to be ignored somehow (The Adafruit uses a 25Mhz crystal.

When I use Si.init(); I get also 14.8 Mhz on the output.

Am I doing something wrong ?

Thanks !

[AtariAndre]

here is the code, basically your demo with added in some (stupid) fixed texts to a OLED display.

/*

• si5351mcu - Si5351 library for Arduino, MCU tuned for size and click-less
• This is the packed simplest example.
• Copyright (C) 2017 Pavel Milanes pavelmc@gmail.com
• Many chunk of codes are derived-from/copied from other libs
• all GNU GPL licenced:
• • Linux Kernel (www.kernel.org)
• • Hans Summers libs and demo code (qrp-labs.com)
• • Etherkit (NT7S) Si5351 libs on github
• • DK7IH example.
• • Jerry Gaffke integer routines for the bitx20 group
• This program 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.
• This program 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
• along with this program. If not, see http://www.gnu.org/licenses/.
  */

/***************************************************************************

• Just put two frequencies out in clk0 and clk1 at different power levels
• Take into account your XTAL error, see Si.correction(###) below
  ***************************************************************************/

#include <DigisparkOLED.h>
#include "si5351mcu.h"

// lib instantiation as "Si"
Si5351mcu Si;

// some variables
long F1 = 16000000; // 16.0 MHz to CLK0

void setup() {
// init the Si5351 lib
Si.init(25000000);

// For a different xtal (from the default of 27.00000 Mhz)
// just pass it on the init procedure, just like this
// Si.init(26570000);

// set & apply my calculated correction factor
// Si.correction(-1250);

// set max power to both outputs
Si.setPower(0, SIOUT_8mA);

// Set frequencies
Si.setFreq(0, F1);

// reset the PLLs
Si.reset();

oled.begin();
oled.setFont(FONT8X16);
//oled.println(millis());"

}
byte bCursor = 0x20;
// the loop routine runs over and over again forever:

void loop() {
oled.setCursor(0, 0); //top left
oled.print(F("Lynx Turbo Boost"));
oled.write(10); // write NewLine [save 30 bytes over println]
oled.write(10); // write NewLine [save 30 bytes over println]
oled.print(F("Frequency 16 Mhz"));
delay(1000); // keep usb alive // can also use SerialUSB.refresh();
oled.write(bCursor = ~bCursor); // Toggle 'SPACE' with some whitish char 223
// do nothing

}

[AtariAndre]

I have now fixed this by changing the value of 27000000 to 25000000 in the library. Now I do get 16 Mhz output. Sometimes the Si5351 doesn't seem to initialize correctly after first upload of the Sketch. power off- on helps.

[AtariAndre]

Mmmm, very strange......very often I now get 25 Mhz instead of 16 Mhz after powering off/on.

weird.

[pavelmc]

Hi Atari Andre, I will check with the hardware at home, but at leas with a Arduino Pro-mini it worked fine 100% of the time... Maybe it's a platform specific condition of the Attinny85 ?

A catch 22 tip: when you power cycle the arduino Attinny85 board the +3.3 voltage in the Si5351 board do get power cycled also?

If not, you are facing a re-initialization problem, a user with a custom board confronted a problem like that a time ago (here in my town) he put a 1000uF cap in the +3.3v and a reset of a fast power cycle does not give time for the +3.3v line to really drop and that cause troubles, a 47uF do the trick for him.

Cheers.