diff --git a/bluetooth/hci/h4_protocol.cc b/bluetooth/hci/h4_protocol.cc
new file mode 100644
index 0000000..97ba7aa
--- /dev/null
+++ b/bluetooth/hci/h4_protocol.cc
@@ -0,0 +1,144 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "h4_protocol.h"
+
+#define LOG_TAG "android.hardware.bluetooth.hci-h4"
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/uio.h>
+
+#include "log/log.h"
+
+namespace android::hardware::bluetooth::hci {
+
+H4Protocol::H4Protocol(int fd, PacketReadCallback cmd_cb,
+                       PacketReadCallback acl_cb, PacketReadCallback sco_cb,
+                       PacketReadCallback event_cb, PacketReadCallback iso_cb,
+                       DisconnectCallback disconnect_cb)
+    : uart_fd_(fd),
+      cmd_cb_(std::move(cmd_cb)),
+      acl_cb_(std::move(acl_cb)),
+      sco_cb_(std::move(sco_cb)),
+      event_cb_(std::move(event_cb)),
+      iso_cb_(std::move(iso_cb)),
+      disconnect_cb_(std::move(disconnect_cb)) {}
+
+size_t H4Protocol::Send(PacketType type, const std::vector<uint8_t>& vector) {
+  return Send(type, vector.data(), vector.size());
+}
+
+size_t H4Protocol::Send(PacketType type, const uint8_t* data, size_t length) {
+  /* For HCI communication over USB dongle, multiple write results in
+   * response timeout as driver expect type + data at once to process
+   * the command, so using "writev"(for atomicity) here.
+   */
+  struct iovec iov[2];
+  ssize_t ret = 0;
+  iov[0].iov_base = &type;
+  iov[0].iov_len = sizeof(type);
+  iov[1].iov_base = (void*)data;
+  iov[1].iov_len = length;
+  while (1) {
+    ret = TEMP_FAILURE_RETRY(writev(uart_fd_, iov, 2));
+    if (ret == -1) {
+      if (errno == EAGAIN) {
+        ALOGE("%s error writing to UART (%s)", __func__, strerror(errno));
+        continue;
+      }
+    } else if (ret == 0) {
+      // Nothing written :(
+      ALOGE("%s zero bytes written - something went wrong...", __func__);
+      break;
+    }
+    break;
+  }
+  return ret;
+}
+
+size_t H4Protocol::OnPacketReady(const std::vector<uint8_t>& packet) {
+  switch (hci_packet_type_) {
+    case PacketType::COMMAND:
+      cmd_cb_(packet);
+      break;
+    case PacketType::ACL_DATA:
+      acl_cb_(packet);
+      break;
+    case PacketType::SCO_DATA:
+      sco_cb_(packet);
+      break;
+    case PacketType::EVENT:
+      event_cb_(packet);
+      break;
+    case PacketType::ISO_DATA:
+      iso_cb_(packet);
+      break;
+    default: {
+      LOG_ALWAYS_FATAL("Bad packet type 0x%x",
+                       static_cast<int>(hci_packet_type_));
+    }
+  }
+  return packet.size();
+}
+
+void H4Protocol::SendDataToPacketizer(uint8_t* buffer, size_t length) {
+  std::vector<uint8_t> input_buffer{buffer, buffer + length};
+  size_t buffer_offset = 0;
+  while (buffer_offset < input_buffer.size()) {
+    if (hci_packet_type_ == PacketType::UNKNOWN) {
+      hci_packet_type_ =
+          static_cast<PacketType>(input_buffer.data()[buffer_offset]);
+      buffer_offset += 1;
+    } else {
+      bool packet_ready = hci_packetizer_.OnDataReady(
+          hci_packet_type_, input_buffer, buffer_offset);
+      if (packet_ready) {
+        // Call packet callback and move offset.
+        buffer_offset += OnPacketReady(hci_packetizer_.GetPacket());
+        // Get ready for the next type byte.
+        hci_packet_type_ = PacketType::UNKNOWN;
+      } else {
+        // The data was consumed, but there wasn't a packet.
+        buffer_offset = input_buffer.size();
+      }
+    }
+  }
+}
+
+void H4Protocol::OnDataReady() {
+  if (disconnected_) {
+    return;
+  }
+  uint8_t buffer[kMaxPacketLength];
+  ssize_t bytes_read =
+      TEMP_FAILURE_RETRY(read(uart_fd_, buffer, kMaxPacketLength));
+  if (bytes_read == 0) {
+    ALOGI("No bytes read, calling the disconnect callback");
+    disconnected_ = true;
+    disconnect_cb_();
+    return;
+  }
+  if (bytes_read < 0) {
+    ALOGW("error reading from UART (%s)", strerror(errno));
+    return;
+  }
+  SendDataToPacketizer(buffer, bytes_read);
+}
+
+}  // namespace android::hardware::bluetooth::hci