diff --git a/src/main/scala/CapturePositions.scala b/src/main/scala/CapturePositions.scala
new file mode 100644
index 0000000..9ed6286
--- /dev/null
+++ b/src/main/scala/CapturePositions.scala
@@ -0,0 +1,104 @@
+package Rs
+
+import chisel3._
+import circt.stage.ChiselStage
+import chisel3.util._
+
+class CapturePositions(c:Config) extends Module {
+  val io = IO(new Bundle {
+    val bitPos = Input(new BitPosIf(c.chienRootsPerCycle))
+    val errPosIf = Output(Valid(new vecFfsIf(c.T_LEN, c.SYMB_WIDTH)))    
+  })
+
+  ////////////////////////////////
+  // Extract position from incomming 
+  // bit vector where bits are asserted
+  ////////////////////////////////
+
+  val extrPos = Module(new ExtractPositions(c.chienRootsPerCycle, c.T_LEN, 4))
+  val numStages = extrPos.numStages
+
+  extrPos.io.in.bits := io.bitPos.pos
+  extrPos.io.in.valid := io.bitPos.valid
+
+  // Shift last
+  val lastQ = Reg(Vec(numStages, Bool()))
+
+  lastQ(0) := io.bitPos.last
+  for(i <- 1 until numStages) {
+    lastQ(i) := lastQ(i-1)
+  }
+
+  ////////////////////////////////
+  // insertVec is used to capture and shift
+  // valid positions into shift register of
+  // length T_LEN.
+  //
+  // outShift is used to remove bubbles in
+  // the shift registers since number of
+  // errors could be less than T_LEN.
+  ////////////////////////////////
+
+  val insertVec = Module(new InsertVec(new PositionsVld,c.T_LEN, c.T_LEN))
+  val baseVec = Reg(Vec(c.T_LEN, new PositionsVld))
+  val vecIn   = Wire(Vec(c.T_LEN, new PositionsVld))
+  val baseCntr = RegInit(UInt(log2Ceil(c.SYMB_NUM).W), 0.U)
+
+  // Final shift
+  val outShift = Module(new BarrelShifter(new PositionsVld, c.T_LEN))
+  val outputVec = Reg(Vec(c.T_LEN, new PositionsVld))
+
+  class PositionsVld extends Bundle {
+    val positions = UInt(c.SYMB_WIDTH.W)
+    val vld = Bool()
+  }
+
+  insertVec.io.vecIn := vecIn
+  insertVec.io.baseVec := baseVec
+  insertVec.io.shiftVal := extrPos.io.outTkeep.map(_.asUInt).reduce(_ +& _)
+
+  outShift.io.vecIn := insertVec.io.vecOut
+  outShift.io.shiftVal := insertVec.io.vecOut.map(bundle => (!bundle.vld).asUInt).reduce(_ +& _)
+
+  // need to add baseCntr to get a proper position:
+  when(extrPos.io.outValid) {
+    when(lastQ(numStages-1)) {
+      baseCntr := 0.U
+      baseVec.foreach(x => x := 0.U.asTypeOf(new PositionsVld))
+      outputVec := outShift.io.vecOut
+      //outputVec := outShift.io.vecOut
+    }.otherwise{
+      baseCntr := baseCntr + c.chienRootsPerCycle.U
+      baseVec := insertVec.io.vecOut
+    }
+  }
+
+  for(i <- 0 until c.T_LEN) {
+    vecIn(i).positions := extrPos.io.positions(i) + baseCntr
+    vecIn(i).vld := extrPos.io.outTkeep(i)
+    io.errPosIf.bits.vec(i) := outputVec(i).positions
+  }
+
+  //io.errPosIf.bits.ffs := Reverse((VecInit(outputVec.map(_.vld))).asUInt)
+  //io.errPosIf.bits.vec := insertVec.io.vecOut
+  
+  io.errPosIf.valid := lastQ(numStages-1)
+  io.errPosIf.bits.ffs := (VecInit(insertVec.io.vecOut.map(_.vld))).asUInt
+  io.errPosIf.bits.vec := (VecInit(insertVec.io.vecOut.map(_.positions)))
+}
+
+object GenCapturePositions extends App {
+
+  val projectRoot = System.getProperty("project.root")
+
+  ConfigParser.parse(args) match {
+    case Some(config) =>
+      JsonHandler.writeToFile(config, "rs.json")
+      // Get 
+      val rsCfg = RSDecoderConfigs.getConfig(config.N_LEN, config.K_LEN)
+      val c = Config(config, rsCfg)
+      ChiselStage.emitSystemVerilogFile(new CapturePositions(c), Array())
+    case None =>
+      sys.exit(1)      
+  }  
+}
diff --git a/src/main/scala/ExtractPositions.scala b/src/main/scala/ExtractPositions.scala
new file mode 100644
index 0000000..da11040
--- /dev/null
+++ b/src/main/scala/ExtractPositions.scala
@@ -0,0 +1,104 @@
+package Rs
+
+import chisel3._
+import circt.stage.ChiselStage
+import chisel3.util._
+
+class ExtractPositions(val InWidth: Int, val PosNum: Int, val pipelineInterval: Int) extends Module {
+  val io = IO(new Bundle {
+    val in = Input(Valid(UInt(InWidth.W)))
+    val positions = Output(Vec(PosNum, UInt(log2Ceil(InWidth).W)))
+    val outTkeep = Output(Vec(PosNum, Bool()))
+    val outValid = Output(Bool())
+  })
+
+  // Number of pipeline stages required
+  val numStages = (InWidth + pipelineInterval - 1) / pipelineInterval
+
+  // Convert input to a vector of Bools
+  val inVec = io.in.bits.asBools
+
+  val prefSumOut = Wire(Vec(InWidth, UInt(log2Ceil(InWidth).W)))
+  val prefSumVldOut = Wire(Bool())
+
+  val inOut = Wire(UInt(InWidth.W))
+  val inQ = Reg(Vec(numStages, (UInt(InWidth.W))))
+  val inVecQ = Reg(Vec(numStages, (Vec(InWidth, Bool()))))
+
+  val prefSumQ = Reg(Vec(numStages, Vec(InWidth, UInt(log2Ceil(InWidth).W))))
+  val vldQ = Reg(Vec(numStages, Bool()))
+  
+  // Compute prefix sum with pipeline registers
+  for (stage <- 0 until numStages+1) {
+
+    val prefSumInit = Wire(Vec(InWidth, UInt(log2Ceil(InWidth).W)))
+    val prefSum = Wire(Vec(InWidth, UInt(log2Ceil(InWidth).W)))
+
+    if(stage == 0) {
+      prefSumInit := VecInit(inVec.map(b => Mux(b, 1.U, 0.U)))
+    } else {
+      prefSumInit := prefSumQ(stage-1)
+    }
+
+    val startIdx = stage * pipelineInterval
+    val endIdx = stage * pipelineInterval + pipelineInterval
+
+    prefSum(0) := prefSumInit(0)
+
+    for(pos <- 1 until InWidth) {
+      if(pos < startIdx)
+        prefSum(pos) := prefSumInit(pos)
+      else if(pos < endIdx)
+        prefSum(pos) := prefSumInit(pos) + prefSum(pos-1)
+      else
+        prefSum(pos) := prefSumInit(pos)
+    }
+
+    if(stage == numStages) {
+      prefSumOut := prefSum.map(b => b - 1.U)
+      prefSumVldOut := vldQ(stage-1)
+      inOut := inQ(stage-1)
+    }
+    else {
+      prefSumQ(stage) := prefSum
+      if(stage == 0) {
+        vldQ(stage) := io.in.valid
+        inQ(stage) := io.in.bits
+      }
+      else {
+        vldQ(stage) := vldQ(stage-1)
+        inQ(stage) := inQ(stage-1)
+      }
+    }
+  }
+
+  // Initialize outputs
+  val positionsReg = Reg(Vec(PosNum, UInt(log2Ceil(InWidth).W)))
+  val outTkeepReg = Reg(Vec(PosNum, Bool()))
+  val outputOutValid = RegInit(false.B)
+
+  // Default assignments
+  for (i <- 0 until PosNum) {
+    positionsReg(i) := 0.U
+    outTkeepReg(i) := false.B
+  }
+
+  // Assign positions
+  for (i <- 0 until InWidth) {
+    when(inOut.asBools(i) && prefSumOut(i) < PosNum.U) {
+      val index = prefSumOut(i)(log2Ceil(PosNum)-1, 0) // Truncate prefSumOut(i) to the correct width
+      positionsReg(index) := i.U
+      outTkeepReg(index) := true.B
+    }
+  }
+
+  // Connect outputs
+  io.positions := positionsReg
+  io.outTkeep := outTkeepReg
+  io.outValid := RegNext(prefSumVldOut, init=false.B )
+  //io.outValid := io.in.valid
+}
+
+object GenExtractPositions extends App {
+  ChiselStage.emitSystemVerilogFile(new ExtractPositions(8, 4, 4), Array())
+}
diff --git a/src/main/scala/InsertVec.scala b/src/main/scala/InsertVec.scala
new file mode 100644
index 0000000..787e390
--- /dev/null
+++ b/src/main/scala/InsertVec.scala
@@ -0,0 +1,38 @@
+package Rs
+
+import chisel3._
+import circt.stage.ChiselStage
+import chisel3.util._
+
+class InsertVec[T <: Data](shiftUnit: T, inWidth: Int, outWidth: Int) extends Module {
+  val io = IO(new Bundle {
+    val baseVec  = Input(Vec(outWidth, shiftUnit))
+    val vecIn = Input(Vec(inWidth, shiftUnit))
+    val shiftVal = Input(UInt(log2Ceil(inWidth+1).W))
+    val vecOut  = Output(Vec(outWidth, shiftUnit))
+  })
+
+  val alignInVec = Module(new AlignInVec(shiftUnit, inWidth, outWidth))
+  val barrelShifter = Module(new BarrelShifter(shiftUnit, outWidth))
+
+  alignInVec.io.vecIn := io.vecIn
+  alignInVec.io.shiftVal := io.shiftVal
+
+  barrelShifter.io.vecIn := io.baseVec
+  barrelShifter.io.shiftVal := io.shiftVal
+
+  // Perform the OR operation element-wise
+  for (i <- 0 until outWidth) {
+    io.vecOut(i) := (barrelShifter.io.vecOut(i).asUInt | alignInVec.io.vecOut(i).asUInt).asTypeOf(shiftUnit)
+  }
+
+}
+
+object GenInsertVec extends App {
+  class ShiftUnit extends Bundle {
+    val formDerSymb = UInt(10.W)
+    val errEvalXlInvSymb = UInt(8.W)
+    val XlSymb = UInt(1.W)
+  }
+  ChiselStage.emitSystemVerilogFile(new InsertVec(new ShiftUnit, 4, 8), Array())
+}