RGB to gray

Let’s imagine a component that converts an RGB color into a gray one, and then writes it into external memory.

io name	Direction	Description
clear	in	Clear all internal registers
r,g,b	in	Color inputs
wr	out	Memory write
address	out	Memory address, incrementing each cycle
data	out	Memory data, gray level

case class RgbToGray() extends Component {
  val io = new Bundle {
    val clear = in Bool()
    val r,g,b = in UInt(8 bits)

    val wr = out Bool()
    val address = out UInt(16 bits)
    val data = out UInt(8 bits)
  }

  def scaled(value : UInt,by : Float): UInt = value * U((255*by).toInt,8 bits) >> 8

  val gray = RegNext(
    scaled(io.r,0.3f) +
      scaled(io.g,0.4f) +
      scaled(io.b,0.3f)
  )

  val address = CounterFreeRun(stateCount = 1 << 16)
  io.address := address
  io.wr := True
  io.data := gray

  when(io.clear) {
    gray := 0
    address.clear()
    io.wr := False
  }
}