Chisel-FFT

NOTE:
The branch BRAM contains codes using BRAM explicitely in FPGA flow.
The branch STFT contains a Chisel-STFT project applied to Short-time Fourier transform.
The branch FFT-Generator contains a project supporting more configurations for the flexiblity of construction and datafromat.This is the latest and most complete version.For more details, please refer to this branch's README.md

This Chisel project implements a R2MDC (Radix-2 Multipath Delay Commutator) FFT hardware design, and the source and test files are organized as follows.

src/
  main/
    scala/
      FFT/ <Chisel的源代码文件>
        Butterfly.scala
        Config.scala
        FFT.scala
        VerilogEmitter.scala
  test/
    scala/
      FFT/ <Chisel的测试代码文件>
        FFTTest.scala

The FPGA folder contains the tcl script and other necessary files for the FPGA flow running on Vivado 2019.2

How to generate Verilog ?

We designed VerilogEmitter.scala to handle all the generations of Verilog code.

In IntelliJ, you can click the green button near the elaborateFFT object defined in VerilogEmitter.scala to run this object and generate Verilog codes.

The object elaborateFFT is defined as follows, and some arguments (like the destination directory, etc) could be configured in this process.

object elaborateFFT extends App {
  (new chisel3.stage.ChiselStage).execute(
    Array("-X", "verilog", "--full-stacktrace"),
    Seq(ChiselGeneratorAnnotation(() => new FFT()),
      TargetDirAnnotation("Verilog"))
  )
}

Or you can run the following command in your terminal.

 sbt 'test:runMain FFT.elaborateFFT'

How to run the test ?

The testbench is defined in FFTTest.scala, and you could run the object FFTTestMain like what we did before to get the simulation results (like the error rate and the overflow rate, etc).

The object FFTTestMain is defined as follows.

object FFTTestMain extends App {
  iotesters.Driver.execute(args, () => new FFT) {
    c => new FFTTest(c)
  }
}

Or you can run the following command in your terminal.

sbt 'test:runMain FFT.FFTTestMain'

How to run the FPGA flow ?

We have already generated three Verilog files FFT128, FFT256 and FFT512 for the FPGA project, which adopts 128, 256 and 512 as the length of FFT. You can import the tcl script directly in the Vivado to run the FPGA implementation and evaluation.

For more information, please see our article published on https://zhuanlan.zhihu.com/p/137260660

Optimization1: Chisel-FFT with reorder buffer

For the complete process of FFT, a reorder buffer hardware is attached to the FFT module, which can be found in

src/
  main/
    scala/
      FFT/ <Chisel的源代码文件>
        Butterfly.scala
        Config.scala
        FFT.scala
        Reorder.scala
        VerilogEmitter.scala

The reorder buffer change the sequences with bit-reversed order to the sequences with normal order. And a new top module is got by connecting the two modules.

How to generater verilog

We designed VerilogEmitter.scala to handle all the generations of Verilog code.

In IntelliJ, you can click the green button near the elaborateFFTReorder object defined in VerilogEmitter.scala to run this object and generate Verilog codes.

The object elaborateFFTReorder is defined as follows, and some arguments (like the destination directory, etc) could be configured in this process.

object elaborateFFTReorder extends App {
  (new chisel3.stage.ChiselStage).execute(
    Array("-X", "verilog", "--full-stacktrace"),
    Seq(ChiselGeneratorAnnotation(() => new FFTReorder()),
      TargetDirAnnotation("Verilog"))
  )
}

Or you can run the following command in your terminal.

 sbt 'test:runMain FFT.elaborateFFTReorder'

How to run the test ?

The testbench is defined in FFTTest3.scala, and you could run the object FFTTestMain3 like what we did before to get the simulation results (like the error rate and the overflow rate, etc).

The object FFTTestMain3 is defined as follows.

object FFTTestMain3 extends App {
  iotesters.Driver.execute(Array("--backend-name", "verilator"), () => new FFTReorder) {
    c => new FFTTest3(c)
  }
}

Or you can run the following command in your terminal.

sbt 'test:runMain FFT.FFTTestMain'

Moreover, we can view the wave of the simualation of the generated verilog by the file with an extension .vcd.

How to run the FPGA flow ?

You need to generate the verilog file for the FPGA project and run the the FPGA implementation and evaluation by yourself