Writing to/Reading from RP registers with SCPI

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jonbean27
Posts: 10
Joined: Thu Jun 11, 2015 9:19 pm

Writing to/Reading from RP registers with SCPI

Post by jonbean27 » Sat Jan 28, 2017 1:41 am

Hey Folks,

As best I can tell, it is impossible to use the standard build's SCPI to write directly to, or read directly from, the FPGA's memory mapped registers-- is this still the case? To be clear: I have generated my own .bit files that repurposes the RP entirely, and I would like to control them remotely. Up to now, I did this with pyRedPitaya, but I'm hoping for a solution which is more easily distributed, as I'd like to make several devices that I've developed available to the public.

In case anyone is interested, the devices I'm planning to share are:
1) a realtime FIR filter with 30000 taps and latency of 2.5uS
2) a 2 channel scriptable triggerable DDS
3) a single channel scriptable triggerable multichromatic DDS which can simultaneously put out up to 20 frequencies

Cheers,
Jon

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Writing to/Reading from RP registers with SCPI

Post by Nils Roos » Sat Jan 28, 2017 2:31 pm

Hi,

you can load your own bitstream with an scpi-command (as long as its name follows the pattern "fpga_*.bit"), but there is no command for accessing addresses directly. In my opinion such a command should be avoided in the scpi-server, it is much better to offer higher level controls for your new logic functions - for example, something to set all the coefficients of your FIR filter.
All in a day's work for Bicycle Repair Man

jonbean27
Posts: 10
Joined: Thu Jun 11, 2015 9:19 pm

Re: Writing to/Reading from RP registers with SCPI

Post by jonbean27 » Sat Jan 28, 2017 5:51 pm

Hi Nils --

Thanks for the quick reply-- I agree completely! What I am trying to avoid is requiring a non-standard OS build to use my .bit files!

Historically I have just provided a full OS distro with the .bit file from our paper (http://aip.scitation.org/doi/10.1063/1.4973470) already included (along with pyRedPitaya, etc...), but this is bulky and inconvenient for users. Maybe I've misunderstood how things are _supposed_ to be done -- is there a facility for this already?

Please assume I'm an idiot and enlighten me, especially if there is a simple approach that I've overlooked -- I know lots about FPGAs and algorithms, and almost zero about doing things easy way -- I'm a physicist, you see :)

Cheers,
Jon

jonbean27
Posts: 10
Joined: Thu Jun 11, 2015 9:19 pm

Re: Writing to/Reading from RP registers with SCPI

Post by jonbean27 » Sun Jan 29, 2017 6:58 pm

should i take this silence to mean that there isn't a simple solution without require modifying things/running additional code on the linux side?

Cheers,
J

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Writing to/Reading from RP registers with SCPI

Post by Nils Roos » Mon Jan 30, 2017 12:31 am

Nah, just take it as a sign that I've got other hobbies besides Red Pitaya.

The 'traditional' method of getting custom stuff into the stock RP ecosystem and controlling it remotely is the bazaar. It provides a simple interface to deploy a zipped folder from a web-location into the RP filesystem and to interactively run the contents.

Although most people associate the bazaar and the web-apps with browser-based interactions, it is also possible to handle the underlying host-side http communication directly, eg. through a python or C program.
All in a day's work for Bicycle Repair Man

jonbean27
Posts: 10
Joined: Thu Jun 11, 2015 9:19 pm

Re: Writing to/Reading from RP registers with SCPI

Post by jonbean27 » Mon Jan 30, 2017 3:44 pm

Thanks Nils! I'll look into that as an option :)

Cheers,
Jon

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