Arduino Math using Nano

Projects Programming
1

I am developing code to have a si5351 replace the crystals of a vintage 2m radio. I need to be able to calculate the frequency of both the receive and transmit crystals. My code for the transmit crystal frequency works but I can't get the the receive code to work. The receive crystal is much higher in frequency, than the transmit crystal. Anyway here is a code fragment, I am grateful for any help.

union longlong  
{
  unsigned long long c;
  unsigned long      a;
  unsigned long      b;

};
union longlong Mylonglong;
unsigned long long ReceiverFreq = 147165000;
void setup() {
  Serial.begin(57600);
  ReceiverFreq = ReceiverFreq - 10700000;
  ReceiverFreq = ReceiverFreq / 3 ;

  Mylonglong.c = ReceiverFreq;
  Serial.print("rec freq ");
  Serial.println(Mylonglong.a, DEC);

  ReceiverFreq = ReceiverFreq * 100L;

  Mylonglong.c = ReceiverFreq;
  Serial.print("rec freq ");
  Serial.println(Mylonglong.a, DEC); // the result I wanr is 454883300
}

void loop() {

}
2

Please give us the actual formula for each type of crystal.

3

This is my output:

rec freq 45488333
rec freq 253866004
4

Thanks:
For receive: CrystalFrequency = (Receive_frequency - 10700000) / 3
my Receive_frequency is 147165000
The Receive crystal frequency has to be multiplied by 100 to work with the si5351
For Transmit : transmitFRequency / 24
My Transmit frequency 147765000
The Transmit crystal frequency has to be multiplied by 100 to work with the si5351

5

That's what I get. I need to get 4548833300 .

6

Why not make it easy on yourself and use floats and mHz with decimal points instead of everything in Hz and guess at the decimal point?

7

Why do you need the names a and b that refer to the same long?
Maybe a and b should be part of a struct?

8

4,548,833,300 = about 4.5 Billion
An unsigned long can only hold about 4.29 billion. You have an overflow.

1 Like
9

... or tack on a "00" in text

10

My first thought as well, but the float math is not accurate enough to give me an accurate crystal frequency.

11

I am trying to convert it to unsigned long long.

12

It will certainly give you any frequency for any crystal you can buy. Remember ALL crystals have a error value that is NOT constant and varies by both temperature and other changes in the circuitry.

13

This is the only way I know of to get Serial.print to print out an unsigned long long, it's only used for debug.

14

Your "way" does not work.

15

It IS an unsigned long long:

unsigned long long ReceiverFreq = 147165000;
  ReceiverFreq = ReceiverFreq - 10700000;
  ReceiverFreq = ReceiverFreq / 3 ;
  ReceiverFreq = ReceiverFreq * 100L;

It's too bad that Serial.print() can't do unsigned long long.

Try this:

void printULL(unsigned long long value)
{
  if (value == 0)
    return;
  printULL(value/10);
  Serial.print(int(value % 10));
}
1 Like
16

You are correct. I just converted an SSB rig to use the si5351. I keep the si5351 in a temperature controlled enclosure to ensure that it stays exactly on frequency.

17

You're more knowledgeable than me, I did what I could with what I know. Thanks for sharing.

18

Nonsense, nothing ever stays exactly on frequency.

19

works great for printing out an unsigned long long. Thanks for sharing

20

You didn't notice the * *? Drift is less than 1 Hz. Good enough for me. I control the enclosure temperature to +- .2 Celcius.