ztoa-team-group-caravel

NOTE: The original non-flattened version of this repo is found here: https://github.com/algofoogle/algofoogle-multi-caravel

Group GFMPW-1 ASIC design organised by "Zero to ASIC" participants

Table of Contents

• Summary
• License
• Die layout
• Design 0: top_raybox_zero_fsm - raybox-zero FSM version
• Design 1: 2nd instance of top_raybox_zero_fsm for characterisation
• Design 2: wrapped_wb_hyperram - Wishbone connected HyperRAM memory driver
• Design 3: user_proj_cpu - CPUy 8-bit CPU
• Design 4: urish_simon_says - Simon Says game for GFMPW-1 Shuttle
• Design 5: top_solo_squash
• Design 6: top_vga_spi_rom
• Mux, including other internal 'test designs'
• Hardening guide
• Running tests

Summary

A team of participants from the Zero to ASIC Course decided to independently assemble this group submission to GFMPW-1 as a way to test/debug/characterise some of their more complex, larger, and experimental designs.

There are 7 designs in this one die, selectable via a mux. Each of the individual designs is referenced below with a link to its original repo.

For my comprehensive notes about the journey to get this submitted, start here with my final journal entry 0189 and work backwards by using the 'Previous journal' link atop each page.

License

This repo is licensed with Apache 2.0.

Die layout

The die layout (as shown in the cover image above) can be downloaded as a PDF: docs/ztoa-team-layout--gfmpw-1.pdf.

Design 0: top_raybox_zero_fsm - raybox-zero FSM version

By: algofoogle (Anton Maurovic) - original repo: raybox-zero @ gf180-for-mux

This project is an attempt to do a minimalist ray caster (Wolf3D-like) VGA renderer in hardware, as a sort of primitive GPU. Earlier, simpler version was previously submitted to be made as part of a community ASIC via the Tiny Tapeout program (see tt04-raybox-zero).

This version features support for an external SPI memory containing wall texture data, and extra registers for changing the appearance of the rendering. It also has a reworked wall tracer.

For additional documentation and details about the project, please see algofoogle/raybox-zero

Design 1: 2nd instance of top_raybox_zero_fsm for characterisation

Same as Design 0 above, but with different placement, different routing via mux.

Design 2: wrapped_wb_hyperram - Wishbone connected HyperRAM memory driver

By: embelon (Pawel Sitarz) - Original repo: wb_hyperram @ 186838b

This is an implementation of a HyperRAM memory driver connected to Wishbone bus.

For additional documentation and details about the project, please see embelon/wb_hyperram

Design 3: user_proj_cpu - CPUy 8-bit CPU

By: dsatizabal (Diego Satizabal) - original repo: cpuy

CPUy is an 8-bits CPU "mind-crafted by experience" and inspired in the AT89S5X series of processors from Atmel which were used by the author at the university to develop microcontrollers projects. The design does not follow any particular well-known architecture for its implementation.

CPUy is meant to be used with an external ROM chip like one of the 27CXXX series that must be flashed with the desired program to be executed supporting a maximum of 4KB of program memory.

The characteristics of CPUy are:

• 10-bits address bus for a maximum external memory of 4096 bytes.
• 8-bits data bus.
• 256 bytes internal scratch pad memory.
• 8 8-bits registers, some used for specific purposes functions as CPU and Timers config.
• 44 supported instructions (arithmetic, logic, branching, movement), some instructions requiring 2 clock cycles and more complex instructions requiring 3 clock cycles for execution.
• 2 bidirectional/configurable I/O ports: P0 8-bits, P1 4-bits.
• 2 16-bits timers with configurable mode (up/down count), autoreload and interrupt.
• 1 dedicated pin for external interrupt.
• 16-levels LIFO stack.
• Combinational-logic ALU and microcode.

For additional documentation and details about the project, please see dsatizabal/cpuy

Design 4: urish_simon_says - Simon Says game for GFMPW-1 Shuttle

By: urish (Uri Shaked) - original repo: gfmpw1-simon-says @ gds_north

Simon says is a simple electronic memory game: the user has to repeat a growing sequence of colors. The sequence is displayed by lighting up the LEDs. Each color also has a corresponding tone.

In each turn, the game will play the sequence, and then wait for the user to repeat the sequence by pressing the buttons according to the color sequence. If the user repeated the sequence correctly, the game will play a "leveling-up" sound, add a new color at the end of the sequence, and move to the next turn.

The game continues until the user has made a mistake. Then a game over sound is played, and the game restarts.

You can play the game using the online Wokwi simulation at https://wokwi.com/projects/371755521090136065. The simulation also shows the wiring diagram.

For additional documentation and details about the project, please see urish/gfmpw1-simon-says

Design 5: top_solo_squash

By: algofoogle (Anton Maurovic) - original repo: solo_squash @ main

This is a Verilog HDL project that implements a primitive digital-logic-based video game that resembles Pong, but with one player just bouncing a ball within a 3-walled space, resembling a game of squash but with just 1 paddle. It also uses a subset of the vertical timing to produce speaker tones for different game states.

For additional documentation and details about the project, please see algofoogle/solo_squash

Design 6: top_vga_spi_rom

By: algofoogle (Anton Maurovic) - original repo: tt05-vga-spi-rom @ main

This is an experiment to see if we can generate a VGA display that uses a constant stream of data from an external SPI ROM, demonstrating a few specific goals:

• Have an option to switch between timing for a 640x480 VGA display and a 1440x900 VGA display using the same source clock.
• Have alternating modes that switch between registered and unregistered output.
• Alternate between Quad SPI mode and single SPI mode.
• Attempt to demonstrate any actual IO, memory, and other logic delays visually.

For additional documentation and details about the project, please see algofoogle/tt05-vga-spi-rom

Mux, including other internal 'test designs'

For documentation on controlling the mux, see: Using LA pins to control the mux

For example firmware, see C source files in test subdirectories of verilog/dv/cocotb/, e.g. hyperram_test.c.

Hardening guide

NOTE: The original repo with all development progress branches can be found on GitHub: https://github.com/algofoogle/algofoogle-multi-caravel

All work branches from gf180-base, which in turn is a simpler<sup id="fnref:1">1</sup> 'template-like' base that branches from efabless/caravel_user_project's gfmpw-1d tag.

Here's a very high-level overview of hardening any given design, assuming you already have at least something of a working OpenLane environment (or at least the prerequisites installed; see the original efabless guide for more info, but note that the PDK version in that doco might be outdated):

NOTE: Zero to ASIC VM also redirects certain other things (MGMT_AREA_ROOT, DESIGNS, CARAVEL_ROOT, etc. to subdirectories of ~/asic_tools/caravel_user_project). Check your ~/.bashrc for details. I've been trying to make this a bit more flexible (see Tip 2312A point 5) but note that I've not completed this work yet.

1. Switch to the branch you want (default for the submission is gf180) set it up for the first time:

   ```bash git checkout gf180 mkdir -p dependencies

   Changing OPENLANE_ROOT & PDK_ROOT optional if using Zero to ASIC VM:

   export OPENLANE_ROOT=$(pwd)/dependencies/openlane_src export PDK_ROOT=$(pwd)/dependencies/pdks

   Required:

   export PDK=gf180mcuD

   This will download and install caravel, the PDK, required OpenLane version, etc.

   make setup ```

2. Each time you want to harden:

   ```bash

   Optional, as above:

   export OPENLANE_ROOT=$(pwd)/dependencies/openlane_src export PDK_ROOT=$(pwd)/dependencies/pdks

   Required:

   export PDK=gf180mcuD

   MAIN HARDENING STEP:

   make top_design_mux ```

3. To harden all:

   bash make top_design_mux \ top_raybox_zero_fsm \ top_solo_squash \ top_vga_spi_rom \ urish_simon_says \ user_proj_cpu \ wrapped_wb_hyperram \ user_project_wrapper

NOTE: The final user_project_wrapper harden is expected to end with reporting hold violations. These are intentional: They relate specifically to secondary reset lines connected to the designs, each controlled by a separate la_data_in[] pin. While other more-stable system-wide reset options are provided, these are intended for specific experimentation/characterisation.

Running tests

Running tests assumes you have set your environment (as above), have run make setup, and have done pip install caravel-cocotb. Additionally, you might also need to use verilog/dv/setup-cocotb.py (or otherwise modify verilog/dv/cocotb/design_info.yaml). For more info, see efabless/caravel_user_project @ gfmpw-1d (or a more recent gfmpw* tag), but note that at the time of writing some of the documentation needs an update or clarification.

Anyway, given a working test environment, you can run (for example):

cd verilog/dv/cocotb
SIM=RTL  # or GL for a much slower and more-thorough gate-level simulation.
RUNTAG=my_RTL_test_run_123  # Set to whatever you want to store results in a specific directory.
caravel_cocotb -sim $SIM -tag $RUNTAG -test mux_test hyperram_test simon_test

Artefacts include .vcd files also for all internal traces of the caravel framework, IOs, and the specific user designs.

Acknowledgements

Thank you to everyone who both contributed to this submission and also helped me along the way:

• embelon (Pawel Sitarz)
• urish (Uri Shaked)
• dsatizabal (Diego Satizabal)

Special thanks goes to:

• Matt Venn who provided great training through the Zero to ASIC course to allow me (and maybe all of us) to get to this point, and who was a vital source of expert knowledge during the more nail-biting moments of wrapping everything up.
• Many helpful and friendly people in the Discord communities of Zero to ASIC and Tiny Tapeout.
• Google, Efabless, and Global Foundries who made this all possible through, respectively: Google's Open MPW program; chipIgnite (and the foundation of all the tooling used to develop/harden this chip); and the GF180 Open PDK.