Electronics > Projects, Designs, and Technical Stuff

IC for function generator

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MarkF:
I see. And since I choose a clock frequency (32.768MHz) with an exact binary value and limited my frequency selection to increments of 1Hz, I always have an exact fraction of the clock. Therefore, no jitter.

Kleinstein:
With the 32,768 MHz clock you can not get a low jitter 4 MHz clock, just from the digital circuit part: One period is somewhat slightly more than 8 clock periods - so most of the time 8 and sometimes 9.

The clock frequency might still have some advantages, as for frequencies that are multiples of 1 kHz the DDS phase increment is a simple value with quite some zeros at the end. This would cause less spurious signals at these frequencies.

rs20:

--- Quote from: MarkF on November 10, 2016, 07:36:11 am ---
--- Quote from: testian on November 08, 2016, 02:47:16 pm ---I will go with the AD9834. Simply because I don't have to worry much about generating a clock signal and the better resolution. Another benefit is the better documentation.
But I will try to make it that way, that the AD9834 could be replace with an AD9102 module.

--- End quote ---

I think you made a wise choice. I spent a little time looking at the AD9102 interface and it looks like it is pretty involved to program. (Not a good choice for the beginner.)

--- End quote ---

Sorry for necro-posting, but I gotta say I disagree with this. Compared to the very real difficulties of doing actual electronics (take handling RF signals, avoiding crosstalk, poor decoupling which can all result in hours of time designing and building a board resulting in an unuseable thing and all the effort going down the drain; or soldering fine pitch components which, if it goes wrong, can spell a frustrating end to the project), "programming" a device like a AD9102 is absolutely trivial. Yes, it would be hard if you had to get it working on the first try. But this is firmware, you don't need to do so at all.  Once you have a board with an AD9102 on it, you can just tinker away. Getting a simple sine wave out of an AD9102 is perfectly straightforward. Then keep slowly adding features.

TL;DR: Needing to modify and rebuild hardware 10 times would be tear-inducingly awful, weeks of pain. Whereas modifying and rebuilding the firmware 10 times is a standard evening of light tinkering/development. The 'difficulties' of an AD9102 fall into the latter category.

MarkF:

--- Quote from: rs20 on June 26, 2019, 01:57:33 am ---
--- Quote from: MarkF on November 10, 2016, 07:36:11 am ---
--- Quote from: testian on November 08, 2016, 02:47:16 pm ---I will go with the AD9834. Simply because I don't have to worry much about generating a clock signal and the better resolution. Another benefit is the better documentation.
But I will try to make it that way, that the AD9834 could be replace with an AD9102 module.

--- End quote ---

I think you made a wise choice. I spent a little time looking at the AD9102 interface and it looks like it is pretty involved to program. (Not a good choice for the beginner.)

--- End quote ---

Sorry for necro-posting, but I gotta say I disagree with this. Compared to the very real difficulties of doing actual electronics (take handling RF signals, avoiding crosstalk, poor decoupling which can all result in hours of time designing and building a board resulting in an unuseable thing and all the effort going down the drain; or soldering fine pitch components which, if it goes wrong, can spell a frustrating end to the project), "programming" a device like a AD9102 is absolutely trivial. Yes, it would be hard if you had to get it working on the first try. But this is firmware, you don't need to do so at all.  Once you have a board with an AD9102 on it, you can just tinker away. Getting a simple sine wave out of an AD9102 is perfectly straightforward. Then keep slowly adding features.

TL;DR: Needing to modify and rebuild hardware 10 times would be tear-inducingly awful, weeks of pain. Whereas modifying and rebuilding the firmware 10 times is a standard evening of light tinkering/development. The 'difficulties' of an AD9102 fall into the latter category.

--- End quote ---

You have got to be kidding!

No RF here.  And both devices have fine pitch.

Minimal documentation!
34 registers with one-line bit descriptions being the total extent of the programming documentation.
A 3-wire or 4-wire SPI interface with two data pins for double SPI transfers.
Far from standard and the double SPI transfer mode would necessitate bit-bang software transfers (i.e. no hardware SPI).

Not for the novice programmer!  Especially for the people who search for libraries to do all the hard work.
Far far far from a trivial interface.
Sure, you turn it on and a sine wave comes out.  Simple.  You're done.  Right?
I predict weeks of trial-and-error and pain.  Then giving up!

Do you want to tinker or accomplish something?


Before you ask...  E.E. degree with 35+ years of professional software development.

ogden:
SPI double mode argument is BS. By default interface is plain 3 wire SPI.

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