diff --git a/openfpga/src/fpga_bitstream/build_mux_bitstream.cpp b/openfpga/src/fpga_bitstream/build_mux_bitstream.cpp
new file mode 100644
index 000000000..3b7e06354
--- /dev/null
+++ b/openfpga/src/fpga_bitstream/build_mux_bitstream.cpp
@@ -0,0 +1,178 @@
+/********************************************************************
+ * This file includes functions to build bitstream from routing multiplexers
+ * which are based on different technology
+ *******************************************************************/
+/* Headers from vtrutil library */
+#include "vtr_log.h"
+#include "vtr_assert.h"
+#include "vtr_vector.h"
+
+/* Headers from openfpgautil library */
+#include "openfpga_decode.h"
+
+#include "mux_utils.h"
+#include "decoder_library_utils.h"
+
+#include "build_mux_bitstream.h"
+
+/* begin namespace openfpga */
+namespace openfpga {
+
+/* Default path ID of a unused multiplexer */
+#define DEFAULT_PATH_ID -1
+
+/* Default path ID of a unused multiplexer when there are no constant inputs*/
+#define DEFAULT_MUX_PATH_ID 0
+
+/********************************************************************
+ * Find the default path id of a MUX
+ * This is applied when the path id specified is DEFAULT_PATH_ID,
+ * which is not correlated to the MUX implementation 
+ * This function is binding the default path id to the implemented structure
+ * 1. If the MUX has a constant input, the default path id will be 
+ *    directed to the last input of the MUX, which is the constant input
+ * 2. If the MUX does not have a constant input, the default path id 
+ *    will the first input of the MUX.
+ *
+ * Restriction:
+ *   we assume the default path is the first input of the MUX
+ *   Change if this is not what you want
+ *******************************************************************/
+size_t find_mux_default_path_id(const CircuitLibrary& circuit_lib,
+                                const CircuitModelId& mux_model,
+                                const size_t& mux_size) {
+  size_t default_path_id;
+
+  if (true == circuit_lib.mux_add_const_input(mux_model)) {
+    default_path_id = mux_size - 1; /* When there is a constant input, use the last path */
+  } else {
+    default_path_id = DEFAULT_MUX_PATH_ID; /* When there is no constant input, use the default one */
+  }
+
+  return default_path_id; 
+}
+
+/********************************************************************
+ * This function generates bitstream for a CMOS routing multiplexer
+ * Thanks to MuxGraph object has already describe the internal multiplexing 
+ * structure, bitstream generation is simply done by routing the signal
+ * to from a given input to the output
+ * All the memory bits can be generated by an API of MuxGraph
+ *
+ * To be generic, this function only returns a vector bit values
+ * without touching an bitstream-relate data structure
+ *******************************************************************/
+static 
+std::vector<bool> build_cmos_mux_bitstream(const CircuitLibrary& circuit_lib,
+                                           const CircuitModelId& mux_model,
+                                           const MuxLibrary& mux_lib,
+                                           const size_t& mux_size,
+                                           const int& path_id) {
+  /* Note that the size of implemented mux could be different than the mux size we see here,
+   * due to the constant inputs 
+   * We will find the input size of implemented MUX and fetch the graph-based representation in MUX library 
+   */
+  size_t implemented_mux_size = find_mux_implementation_num_inputs(circuit_lib, mux_model, mux_size);
+  /* Note that the mux graph is indexed using datapath MUX size!!!! */
+  MuxId mux_graph_id = mux_lib.mux_graph(mux_model, mux_size);
+  const MuxGraph mux_graph = mux_lib.mux_graph(mux_graph_id);
+
+  size_t datapath_id = path_id;
+
+  /* Find the path_id related to the implementation */
+  if (DEFAULT_PATH_ID == path_id) {
+    datapath_id = find_mux_default_path_id(circuit_lib, mux_model, implemented_mux_size);
+  } else { 
+    VTR_ASSERT( datapath_id < mux_size);
+  }
+  /* Path id should makes sense */
+  VTR_ASSERT(datapath_id < mux_graph.inputs().size());
+  /* We should have only one output for this MUX! */
+  VTR_ASSERT(1 == mux_graph.outputs().size());
+
+  /* Generate the memory bits */
+  vtr::vector<MuxMemId, bool> raw_bitstream = mux_graph.decode_memory_bits(MuxInputId(datapath_id), mux_graph.output_id(mux_graph.outputs()[0]));
+
+  std::vector<bool> mux_bitstream;
+  for (const bool& bit : raw_bitstream) {
+    mux_bitstream.push_back(bit);
+  }
+
+  /* Consider local encoder support, we need further encode the bitstream */
+  if (false == circuit_lib.mux_use_local_encoder(mux_model)) {
+    return mux_bitstream;
+  }
+
+  /* Clear the mux_bitstream, we need to apply encoding */
+  mux_bitstream.clear();
+
+  /* Encode the memory bits level by level,
+   * One local encoder is used for each level of multiplexers 
+   */
+  for (const size_t& level : mux_graph.levels()) {
+    /* The encoder will convert the path_id to a binary number 
+     * For example: when path_id=3 (use the 4th input), using a 2-input encoder 
+     * the sram_bits will be the 2-digit binary number of 3: 10
+     */
+    std::vector<size_t> encoder_data;
+
+    /* Exception: there is only 1 memory at this level, bitstream will not be changed!!! */
+    if (1 == mux_graph.memories_at_level(level).size()) {
+      mux_bitstream.push_back(raw_bitstream[mux_graph.memories_at_level(level)[0]]);
+      continue;
+    }
+
+    /* Otherwise: we follow a regular recipe */
+    for (size_t mem_index = 0; mem_index < mux_graph.memories_at_level(level).size(); ++mem_index) {
+      /* Conversion rule: true = 1, false = 0 */
+      if (true == raw_bitstream[mux_graph.memories_at_level(level)[mem_index]]) {
+        encoder_data.push_back(mem_index);
+      } 
+    }
+    /* There should be at most one '1' */
+    VTR_ASSERT( (0 == encoder_data.size()) || (1 == encoder_data.size()));
+    /* Convert to encoded bits */
+    std::vector<size_t> encoder_addr;
+    if (0 == encoder_data.size()) { 
+      encoder_addr = itobin_vec(0, find_mux_local_decoder_addr_size(mux_graph.memories_at_level(level).size()));
+    } else {
+      VTR_ASSERT(1 == encoder_data.size());
+      encoder_addr = itobin_vec(encoder_data[0], find_mux_local_decoder_addr_size(mux_graph.memories_at_level(level).size()));
+    }
+    /* Build final mux bitstream */
+    for (const size_t& bit : encoder_addr) {
+      mux_bitstream.push_back(1 == bit);
+    }
+  } 
+
+  return mux_bitstream;
+}
+
+/********************************************************************
+ * This function generates bitstream for a routing multiplexer
+ * supporting both CMOS and ReRAM multiplexer designs 
+ *******************************************************************/
+std::vector<bool> build_mux_bitstream(const CircuitLibrary& circuit_lib,
+                                      const CircuitModelId& mux_model,
+                                      const MuxLibrary& mux_lib,
+                                      const size_t& mux_size,
+                                      const int& path_id) {
+  std::vector<bool> mux_bitstream;
+
+  switch (circuit_lib.design_tech_type(mux_model)) {
+  case CIRCUIT_MODEL_DESIGN_CMOS:
+    mux_bitstream = build_cmos_mux_bitstream(circuit_lib, mux_model, mux_lib, mux_size, path_id);
+    break;
+  case CIRCUIT_MODEL_DESIGN_RRAM:
+    /* TODO: ReRAM MUX needs a different bitstream generation strategy */
+    break;
+  default:
+    VTR_LOGF_ERROR(__FILE__, __LINE__,
+                   "Invalid design technology for circuit model '%s'!\n",
+                   circuit_lib.model_name(mux_model).c_str());
+    exit(1);
+  }
+  return mux_bitstream;
+}
+
+} /* end namespace openfpga */
diff --git a/openfpga/src/fpga_bitstream/build_mux_bitstream.h b/openfpga/src/fpga_bitstream/build_mux_bitstream.h
new file mode 100644
index 000000000..639e086bc
--- /dev/null
+++ b/openfpga/src/fpga_bitstream/build_mux_bitstream.h
@@ -0,0 +1,30 @@
+#ifndef BUILD_MUX_BITSTREAM_H
+#define BUILD_MUX_BITSTREAM_H
+
+/********************************************************************
+ * Include header files that are required by function declaration
+ *******************************************************************/
+#include <vector>
+#include "circuit_library.h"
+#include "mux_library.h"
+
+/********************************************************************
+ * Function declaration
+ *******************************************************************/
+
+/* begin namespace openfpga */
+namespace openfpga {
+
+size_t find_mux_default_path_id(const CircuitLibrary& circuit_lib,
+                                const CircuitModelId& mux_model,
+                                const size_t& mux_size);
+
+std::vector<bool> build_mux_bitstream(const CircuitLibrary& circuit_lib,
+                                      const CircuitModelId& mux_model,
+                                      const MuxLibrary& mux_lib,
+                                      const size_t& mux_size,
+                                      const int& path_id);
+
+} /* end namespace openfpga */
+
+#endif