satcat5 VS chisel

I needed 128-bit and 256-bit integers on an embedded project recently.

In short, it was for fixed-point digital signal processing. The raw input and output samples were int64_t. We needed to add, subtract, multiply, and accumulate these to do filtering and linear regression with no loss of precision.

Conventional bigintegers weren't an option because the target application doesn't allow heap allocation. So we rolled our own [1] stack-allocated, fixed-width big integer class.

[1] https://github.com/the-aerospace-corporation/satcat5/blob/ma...

And here's an open-source implementation I wrote a few years back. You can skip the part at the end that handles variable-length trailing bytes, since you have a fixed-width input.

My SatCat5 project also has a few options. Anything under src/vhdl/common/cfgbus_* can be connected to AXI or Wishbone with a simple adapter.

For an all-digital solution, here's an NCO that generates an arbitrary-frequency square wave from a numeric counter.

My first instinct was to ask "Does this play well with CIRCT?" And thankfully they answer that right away in the README.

I'm personally of the opinion that there is a LOT of room for improvement in the hardware design tooling space, but a combination of market consolidation, huge pressure to meet deadlines, and an existing functional pipeline of Verilog/VHDL talent is preventing changes.

That's not to say "Verilog/VHDL are bad", because clearly they've been good enough to support nearly all of the wonderful designs powering today's devices. But it is to say, "the startup scene for hardware will continue to look anemic compared to the SaaS scene until someone gives me all of the niceties I have for building SaaS tools in software."

A huge amount of ideas (and entire designs) start off as software sims, which enables kernel/compiler engineers to start building out support for new hardware before it's manufactured.

There is some interesting work going on at SiFive building hardware with Chisel[1], as well as some interesting work lead by a professor at William and Mary to improve simulations[2].

1: https://www.chisel-lang.org

2: https://github.com/sarchlab/akita

Inspired by Scala. Which can do a whole lot more, and worse. The currently biggest competitor to decades old hardware description languages is a Scala DSL.

Already mentioned Chisel: https://www.chisel-lang.org/

I'm also a hobbyist. There are a number of alternative HDLs out there, and as hobbyists we can deviate more from the mainstream of (System)Verilog and VHDL if we desire, though you'll still need to be able to read them. In the past I've done Verilog, but lately I've been using SpinalHDL and have been really enjoying it. Its close relative Chisel also makes appearances in the RISC-V space.

What are your thoughts on other HDLs like Chisel or BlueSpec when it comes to better type checking?

I started playing with FPGAs and HDLs a couple years ago with no hardware design background (I'm mostly a software architect/engineer) and in the end found that a "higher-level" HDL suited me better.

I chose Chisel (https://www.chisel-lang.org/) an HDL based on Scala (technically a Scala DSL) which can provide many facilities to hardware generation.

I'd highly advise looking into it although also knowing Verilog helps a lot.

But some go further and ask "what if when we add a soldering station on top of it?"

In recent years Chisel HDL, RISC V, and SiFive came out of their architecture group, to name a few.