Chisel Tips

This page lists some tips for Chisel that I could glean here and there.

UInt() to Vec()

An UInt() can be converted to a Vec of Bool() with asBools:

val foo = Vec(5, Bool())
val bar = UInt(5.W)

foo := bar.asBools
Initialize Vec() of Reg()

Initialize Vec() of Reg()

 val initRegOfVec = RegInit(VecInit(Seq.fill(4)(0.U(32.W))))

Concatenate value in one UInt()

Of course we can use Cat(), but it take only 2 parameters. With ‘##’ we can chain more signals:

val a = Reg(UInt(1.W))
val b = Reg(UInt(1.W))
val c = Reg(UInt(1.W))
val y = Reg(UInt(3.W))

y := a ## b ## c

Test some chisel code in console

It can be usefull to be able to test code in console before launching the big compilation. It’s possible in directory where your project build.sbt is :

$ cd myproject/
$ sbt
sbt:myproject> console
scala>

And once in the scala console chisel import can be done :

scala> import chisel3._
import chisel3._
scala> val plop = "b0010101010001".U(13.W)
plop: chisel3.UInt = UInt<13>(1361)

Type Ctrl+D to quit.

For more Chisel Cookbook

See the official cookbook on chisel website.

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