Sweep frequency DDS

jbroz

han94ros Will do. So far, I've just been playing with the amplitude modulation. But for the most part I'm doing everything the same way as you and it seems to be working fine. I don't know how much there is to improve.

I'm still surprised that you can't set the profiles individually for the different DDS chips on the board (if this is, in fact, the case -- though, I haven't tested it yet).

Also, thanks for pointing out the osk_enable hack! I'm sure that will save me some time tomorrow.

han94ros

jbroz Sure no worries, I am also working on the amplitude modulation today and perhaps we can compare codes. I will post it here after I have completed it.

han94ros

jbroz Have you been able to find a workaround to setting different modulation profiles for the different chips/channels on the board?

I can only seem to run this script on a single channel, it is suprising the RAM cannot be made to output to more than one channel simulatenously.

han94ros

jbroz seems to work if you do not disable the RAM when writing the waveform to another chip/channel. This allows for the setting of independent frequency modulated signals to the different chips.

It says in the manual however that it is strongly recommended that RAM_enable = 0 when performing load/retrieve operations - do you believe writing to the RAM whilst it is still enabled would cause any damage.

jbroz

Ahh, that makes sense. I think the warning in the manual doesn't apply since the load/retrieve operations are just being performed on a single DDS (even though we've switched the profile setting on all of them). But I could be wrong.

isaac

airwoodix Is there any update on the DRG api development mentioned in #1344?

airwoodix

isaac Not that I know of. But @rjo surely knows better.

isaac

airwoodix Thanks for the information.
rjo Exposure of the DRG api would simplify the programming significantly in some frequency sweep tasks. Is there any advice on what I can do since I really need the function?

rjo

No additional interest or development that I know of.

rjo

As always: fund the development and talk to people that can implement it or if you feel up to it, do it yourself.

isaac

rjo Okay, got it.

han94ros

isaac why can't you simulate the ramp using the RAM mode?

isaac

han94ros Thanks for the advice. In fact, I've implemented a workable solution with DMA. But I still think that being able to get direct access to DRG would enable us to tackle the problem in a more elegant way.

occheung

airwoodix
I tried your method and the DDS frequency was stuck in the lower limit for >250 us.

I am not sure how to control/eliminate the time gap (where its stuck at lower limit). Couldn't find anything relevant in the datasheet. Alternatively I have fixed the DRCTL pins to high in the CPLD, and just use the increment fields instead. This is what I got by combining the DRG (frequency) and RAM (amplitude).

Amplitude and frequency changes simultaneously at a defined interval.

~~Are there any interest for this CPLD patch?~~
Nvm, just enable load LRR @ I/O Update in CFR1. See the DRG usage in ARTIQ.

« Previous Page