fixed point support on Chisel hdl

I am new to Chisel HDL, and I found the Chisel HDL does provide fixed point respresentation. (I found this link: Fixed Point Arithmetic in Chisel HDL)

when I try it in the chisel hdl it actually doesn't work:

import Chisel._

class Toy extends Module {
        val io = new Bundle {
                val in0 = SFix(4, 12).asInput
                val in1 = SFix(4, 12).asInput
                val out = SFix(4, 16).asOutput
                val oraw = Bits(OUTPUT, width=128)
        }
        val int_result = -io.in0 * (io.in0 + io.in1)
        io.out := int_result
        io.oraw := int_result.raw
}

class ToyTest(c: Toy) extends Tester(c) {
        for (i <- 0 until 20) {
                val i0 = 0.5
                val i1 = 0.25
                poke(c.io.in0, i0)
                poke(c.io.in1, i1)

                val res = -i0 * (i0+i1)
                step(1)
                expect(c.io.out, res)
        }
}

object Toy {
        def main(args: Array[String]): Unit = {
                val tutArgs = args.slice(1, args.length)
                chiselMainTest(tutArgs, () => Module(new Toy())) {
                        c => new ToyTest(c)
                }
        }
}

which produce the error that:

In my build.sbt file, I choose the latest release chisel by:

libraryDependencies += "edu.berkeley.cs" %% "chisel" % "latest.release"

Solution

According to Chisel code SFix seems to be deprecated, Fixed should be used instead. I modified your code to use it, but there is a problem with poke and expect. It seems that Fixed is not supported yet by poke and expect.

import Chisel._

class Toy extends Module {
        val io = new Bundle {
                val in0 = Fixed(INPUT, 4, 12)
                val in1 = Fixed(INPUT, 4, 12)
                val out = Fixed(OUTPUT, 8, 24)
                val oraw = Bits(OUTPUT, width=128)
        }
        val int_result = -io.in0 * (io.in0 + io.in1)
        io.out := int_result
        io.oraw := int_result.asUInt()
}

class ToyTest(c: Toy) extends Tester(c) {
        for (i <- 0 until 20) {
                val i0 = Fixed(0.5, 4, 12)
                val i1 = Fixed(0.25, 4, 12)
                c.io.in0 := i0
                c.io.in1 := i1
                //poke(c.io.in0, i0)
                //poke(c.io.in1, i1)

                val res = -i0 * (i0+i1)
                step(1)
                //expect(c.io.out, res)
        }
}

object Toy {
        def main(args: Array[String]): Unit = {
                val tutArgs = args.slice(1, args.length)
                chiselMainTest(tutArgs, () => Module(new Toy())) {
                        c => new ToyTest(c)
                }
        }
}