Alright, thank you all for the support,

as usual I started too fast... well:=A0

answer to question 1: I have to build a=A0local oscillator, so rotating an =
encoder=20
or using a keyboard, I have to set the frequency value in MHz.

answer to question 2: To get that frequency value into the DDS, I have to s=
end a=20
32bit word into the DDS via serial port.

No matter, so far, about sending bytes to the DDS (I'll take a look to spec=
ific=20
app notes later), the trouble now comes when I have to manage frequency val=
ue=20
and get it in 32bit.

The formula is M =3D (f0 * 2^32)/fc=20

M is the 32bit word to send to the DDS
f0 is the variable that=A0user may change
fc is the DDS clock (assume it 50MHz)

I'll have 4 bytes to send to the DDS: W1 W2 W3 and W4.
W1 is the=A0"upper" byte containing bit=A031=A0and W4 is the "lower" byte c=
ontaining=20
bit 0.=20

Sending procedure will start from the LSB of W4 (bit 0) ending with MSB in =
W1=20
(bit 32).=20

Then, another word will be sent, but this won't be a problem because there =
won't=20
be changes in it.

So, at the end, my problem is not how to cut 32bit in 4 but how to manage t=
he=20
frequency and the 32bit word.=20

It comes obvious that I have to think ALWAYS about 4 bytes while doing the=
=20
calculations. That's hard for me... but maybe I can do it :-)=A0=A0
I planned to set a start frequency and let the PIC do the first calculation=
 to=20
send the first M in the DDS (this could be also the last frequency memorize=
d or=20
simply a "reset value" related to an external switch).

First of all, I thought about mikrobasic language bue to the 32bit word, bu=
t I=20
do not really like to write in basic, I want to try in ASSY. Only if f I wi=
ll=20
fail, I'll get back to mikrobasic: I own a mikroe EasyPIC5 board... but I a=
lways=20
used MPLAB to program.

So, that's all so far, I am coming back to programming and this is a true=20
challenge for me, thank you once againn for your help.
Matteo


--=20
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