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Setting up Hifiberry DSP Addon in piCorePlayer (so far)

tom roth

December 10, 2024 14:18

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Greetings

The Hifiberry DSP looks like a promising and affordable option to do DSP in hardware.
Unfortunately documentation especially on installation outside of Hifiberry OS is hard to find. 
I managed to get it running in piCorePlayer and would like to share my experiences here:

https://sites.google.com/view/theaudioniche/hifiberry-dsp

I hope this might help others in the same situation.
Also i would be thankful for correction on where i got things wrong.

And then there are concepts i am still struggling with:
- store_attributes stores attributes from RAM into DSP EEPROM.
When is this necessary? 
- Is this RAM of the DSP or of the Pi?
- Will a set_fir_filter command just write into RAM?
- Will apply-rew-filters make filters persistent or will they be gone after a reboot.
- Is there any documentation how filesystem, RAM and eeprom are working together?
- When i start sigmatcpserver with a host IP could i interact using a hifiberry instance running on another system?
- Is there an option or config to tell dsptoolkit what IP to use to talk to sigmatcpserver.
- Can i connect Sigma Studio to sigmatcpserver and read/send values of dsp?
- Is there a profile that provides a convolver?

Should i open a new post for every question a have?

 

 

 

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6 comments

• 0
  
  HiFiBerry team December 10, 2024 14:30

  >- store_attributes stores attributes from RAM into DSP EEPROM.
  > Is this RAM of the DSP or of the Pi?

  If an attribute is defined as storable, it will by written to the EEPROM with 
  dsptoolkit store
  This basically creates a new DSP profile with these registers set to their current values
  This is only for the DSP memory. 

  Any changes ôn the DSP (filters, registers, ...) are not persistant if the attribute is not stored.

  > Is there any documentation how filesystem, RAM and eeprom are working together?
  No. Basically the files on the file system are just there for the metadata. The DSP will run even without DSPToolkit installed at all. However, the dsptoolkit need the DSP profile on the file system for the metadata. Without this, it can't control specific functions as the mapping of functions to registers is only defined in the XML file.

  >  Is there a profile that provides a convolver?
  > Will a set_fir_filter command just write into RAM?
  Looks like you want to run FIR filters. Be aware, that you can't just copy/paste filter coefficients from some tools. This is a fixed point DSP and you would have to optimize coefficients for the specific architecture. We only recommend these to users that know the SigmaDSP architecture and their limitations in detail!
  
  > When i start sigmatcpserver with a host IP could i interact using a hifiberry instance running on another system?
  > Is there an option or config to tell dsptoolkit what IP to use to talk to sigmatcpserver.
  The --host option can control a server on another host if it's available over the network. Just run
  dsptoolkit -h
  to see the supported command line options
  
  > Should i open a new post for every question a have?
  No

• 0
  
  tom roth December 10, 2024 22:49

  Thank you a lot. This was helpful.

  Let me rephrase to see if I got it all correct:
  When the dsp is powered up it loads it’s profile from eeprom.
  The profile defines registers and their (default) values.
  Changes to registers done by dsptoolkit change the behavior of the dsp instantly but are lost after a powercycle.
  To make these changes persistent dsptoolkit store writes these values to eeprom, thereby creating a new prolife.
  Dsptoolkit install-profile would therefore also reset the active values back to their defaults.
  Some registers like sensitivitySPDIFRegister, are not storable.
  The metadata in the dspprofile is quasi a config file for dsptoolkit.
  Therefore after loading a profile it is important not to move or delete the file nor change the metadata.
  This point is especially important with piCorePlayer as files are not persistent there.
  Starts to make sense.

  I am fine with using iir filters generated by REW for now, but would like to have an idea how difficult it would be to also do phase correction. From your answer I gather it not being likely there will be a dsptoolkit apply-convolution impulse-response.wav provided by Hifiberry in the near future.

  The —host option is cool though.

  Another question: is it possible to read register values from dsp.
  Dsptoolkit save writes dspparameters.dat.
  Are these the values active in dsp?
  How can this file be read? Sigma Studio?
  What is the read-reg function doing?
  Is the address for this command the number in the metafile?
  Will dsptoolkit read-reg 57 give me the volume level?

  Edited by tom roth December 10, 2024 22:54
• 0
  
  HiFiBerry team December 11, 2024 07:48

  Just to clarify the definitions here:
  
  A DSP program is a set of command that the DSP runs. It is basically program code of the DSP. This also includes register settings.This is machine code of the DSP.
  
  A DSP profile wraps the DSP program and some metadata into an XML file that can be processed with dsptoolkit. Without this DSP profile, dsptoolkit doesn't know anything about the program that runs on the DSP.
  
  read-reg and read-mem just allow you access the memory of the DSP. The DSP has basically 2 different types of memory: RAM and registers. RAM cells are 32bits, registers 16 bits.

  > Will dsptoolkit read-reg 57 give me the volume level?
  
  No, it will just read 16bit at address 57. What's in there depends on the program that runs on the DSP. The XML file included the metadata what function is stored at what memory address. This will be totally different for different programs. 
  
  > is it possible to read register values from dsp.
  Yes, check the command line options of dsptoolkit by simply running dsptoolkit -h

  To fully understand the whole program/RAM/register setting, you need to understand the architecture and the internals of the DSP in use.
  DSP Profiles are our way to abstract these that you don't have to deal with these but can use commands like set-volume

  > From your answer I gather it not being likely there will be a dsptoolkit apply-convolution impulse-response.wav provided by Hifiberry in the near future.
  That's correct. While the DSP can handle FIR filters, due to it's fixed-point architecture, it's not really the best choice for very long FIR filters with lots of coefficients that are not zero.

• 0
  
  tom roth December 11, 2024 09:07

  Thanks for clarifying the definitions, that helps a lot.
  dsptoolkit -h is what I did. And often. Problem is, it just gives the names of the commands that can be used.
  It neither tells what the commands do nor what parameters can be used. I dived in the source code to find out how to use tonecontrol.
  I think dsptoolkit -h would be a lot more useful if it provided this information. This could be easily achieved by using python argparser.
  Output then would look like:
  …
  tonecontrol sets a highshelf or lowshelf filter

  I understand that your target audience is the inexperienced user who wants to click on colorful icons.
  And i applaud your effort to bridge that canyon of complexity.
  Yet to become an advanced user and for the community to participate in improving your product, I think good documentation is key.

  I would offer to write such an argparser for dsptoolkit and provide a pull request.
  Yet I am not sure whether you are interested to accept such an effort.

• 0
  
  HiFiBerry team December 11, 2024 09:16

  Sure, feel free to send a PR. We're always open to this kinds of improvements.
  
  Note that dsptoolkit is just a low-level tools. While there is some handling of REW filters, it is only designed to deal with stuff like memory cells and registers. Something like "tone control" would require some additional functionality.

• 0
  
  tom roth December 11, 2024 13:35

  i just opened a pull request

  https://github.com/hifiberry/hifiberry-dsp/pull/70