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Pulpissimo progress

Aug 11, 20246 min read

Pulpissimo

Outstanding questions

none at this time

Progress

2024-07-30

  • Implementation properties — change some strategies
  • Install FrontPanel software
  • Use JTAG to download the bitstream
  • Check if board is actually receiving inputs
  • Modify pin assignments
  • Roberto to find cable
  • Study how they assign JTAG pins and change it on the board
  • 4 things
    • Fix any hold time violations by changing implementation strategy on Vivado
    • Install OpalKelly FrontPanel software and try to download the bitstream to the board
    • Study current pin assignments (intended for Genesys board) and adapt to OpalKelly board using the existing constraint file
    • Checking the options for JTAG communication to the board
      • JTAG may not be necessary

2024-07-29

  • Bitstream has been built. Some notes:
    • Vivado currently mentions possible hold time violations, due to bad/faulty connections.
    • Also possible poor usage of resources: Vivado assumes certain ports are registers (perhaps not mapping RAM correctly?).
  • Also rebuilt OpenOCD from source. Pulpissimo requires a custom version of OpenOCD since there’s a longstanding issue with the official RISC-V OpenOCD port.

2024-07-26

  • Trying to compile any arbitrary bitstream (verifying it’s not a problem with the custom part I tried to input). So far none of the Digilent Nexys boards are compiling and neither is the Xilinx ZCU104.
    • For Digilent boards, it doesn’t even launch Vivado. I suspect either a problem with the installed Vivado version (I’m unsure of this, since 2022.1 was a suggested version for the Digilent boards) or the files were not correctly installed.
    • For the ZCU104, the compilation’s killed past a certain point. I believe this is due to insufficient RAM memory.
      • This fix was to create an extra swap memory partition, which Vivado relies on.
  • Replicated a new build process for the OpalKelly ZEM7310.

2024-07-25

  • Mustafa is away with COVID and is unable to hand over the Arty Z7.
  • In lieu of this, Roberto suggested attempting to build a bitstream for the Opal Kelly XEM7310 (with a Xilinx Artix-7)
  • I’ve been having space issues with the Vivado installation — 2022.1 requires 150 GB free and my Linux machine only had ~30 GB free
    • I’ve since wiped the Windows 11 install on my Linux machine and repartitioned it as a Linux filesystem drive
    • Installed Vivado on a newly partitioned drive
  • So far running into problems relating to dependencies — Vivado is telling me that the specific board part isn’t found, even if it’s definitely installed (and verifiable with the get_board_parts Tcl command)

2024-07-24

  • Mustafa has a Digilent Arty Z7 but this is unverified to work and missing a power supply cable
  • Spent today running regression tests and familiarising myself with the codebase more

2024-07-23

  • Currently running regression tests — previous script that automated each test is no longer available
    • Most tests working, exceptions include: machine learning tests, I2C
  • Meeting notes
    • Progress — simple runtime working with Questa, most tests are working with some exceptions
    • Outstanding questions
      • If I run into problems with Questa, I’d need to ask the professor to create a user for me on the ECE (graduate?) machines and give access to a license
      • Re: communication, a weekly sync meeting looks like the best option. I can reach out to Roberto via Discord if I run into any problems
    • Previous PULP work
      • SDK was previously not explored, since the simple runtime required a significant amount of set-up/fix work from the previous student. Once the simple runtime was working, they went straight to the FPGA implementation
      • Pulpissimo was taped out, not the full PULP SoC or just the smaller RI5CY core
      • Main purpose of Pulpissimo was to do “mask generation” for one of the image sensor group’s projects — there were three main platforms taped out: 2 mask accelerators that were custom designed, and a RISC-V microcontroller that would generate arbitrary masks
        • The mask accelerators were debugged, but not the RISC-V core. This is probably going to be my responsibility
    • Next steps
      • Can start working with FPGA board, Genesys 2, Nexys 2, Nexys Video; to contact Mustafa to get a board
      • To learn how to use OpenOCD to program the board with JTAG and figure out a communication system between the FPGA and ASIC
      • If there’s remaining time and/or interest, we can think about possible custom modifications (not specific)

2024-07-22

2024-07-19

  • Runtime is now working with hello world example in Questa — some notes
    • Simple runtime works as promised in the repository
    • SDK is not working whatsoever — I’ve tried around 5 different build methods and the C++ requires a few dozen hotfixes at compile-time. Python incompatibilities as well within the code
    • Python 3.{11, 12} breaks the runtime build — this requires a small hotfix with the string 'rU' to just 'r'
    • We’re running the most recent version of Pulpissimo and the GNU toolchain — there are likely material changes and fixes from when the previous student was using this in 2022
  • Shell commands above for best reproducibility

2024-07-18

  • Recompiling RISC-V GNU toolchain: two main problems I’m facing with recommended build settings
    • Original path settings don’t properly compile binary files
      • Changing this to a less permissive directory fixes a problem with a missing GCC binary
    • Architecture settings do not actually build for Pulp, but instead a generic arch
  • Potentially going to run into problems with Questa. Currently running on Questa Intel FPGA Starter Version — so far Pulpissimo has been able to build with Questa but:
    • Performance issues compared to full edition of Questa
    • Potential to stall due to unsupported simulation settings between full/starter versions of Questa
    • Resolved by getting a full license of ModelSim/Questa — past student worked with lab computers for this

2024-07-17

  • Software installations, Git repository cloning
    • Able to build Pulpissimo with Questa
  • Path problems with Questa, toolchain — later resolved

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