diff --git a/.gitignore b/.gitignore
index 89e509d..ba5791d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -152,4 +152,7 @@ cython_debug/
 #.idea/
 
 # VSCode
-.vscode/
\ No newline at end of file
+.vscode/
+
+# Secrets file
+.secrets.yml
diff --git a/hci.py b/hci.py
new file mode 100644
index 0000000..7aaffed
--- /dev/null
+++ b/hci.py
@@ -0,0 +1,73 @@
+import base64
+import subprocess
+from time import sleep
+from struct import pack
+
+
+class HCIBroadcaster:
+    def __init__(self, b64key):
+        self.key = base64.b64decode(b64key)
+
+    def _advertisement_template():
+        adv = ""
+        adv += "1e"  # length (30)
+        adv += "ff"  # manufacturer specific data
+        adv += "4c00"  # company ID (Apple)
+        adv += "1219"  # offline finding type and length
+        adv += "00"  # state
+        for _ in range(22):  # key[6:28]
+            adv += "00"
+        adv += "00"  # first two bits of key[0]
+        adv += "00"  # hint
+        return bytearray.fromhex(adv)
+
+    def _bytes_to_strarray(self, bytes_, with_prefix=False):
+        if with_prefix:
+            return [hex(b) for b in bytes_]
+        else:
+            return [format(b, "x") for b in bytes_]
+
+    def _run_hci_cmd(self, cmd, hci="hci0", wait=1):
+        cmd_ = ["hcitool", "-i", hci, "cmd"]
+        cmd_ += cmd
+        print(cmd_)
+        subprocess.run(cmd_)
+        if wait > 0:
+            sleep(wait)
+
+    def start_advertising(self, interval_ms=2000):
+        key = self.key
+        addr = bytearray(key[:6])
+        addr[0] |= 0b11000000
+
+        adv = self._advertisement_template()
+        adv[7:29] = key[6:28]
+        adv[29] = key[0] >> 6
+
+        print(f"key     ({len(key):2}) {key.hex()}")
+        print(f"address ({len(addr):2}) {addr.hex()}")
+        print(f"payload ({len(adv):2}) {adv.hex()}")
+
+        # Set BLE address
+        self._run_hci_cmd(
+            ["0x3f", "0x001"] + self._bytes_to_strarray(addr, with_prefix=True)[::-1]
+        )
+        subprocess.run(["systemctl", "restart", "bluetooth"])
+        sleep(1)
+
+        # Set BLE advertisement payload
+        self._run_hci_cmd(
+            ["0x08", "0x0008"] + [format(len(adv), "x")] + self._bytes_to_strarray(adv)
+        )
+
+        # Set BLE advertising mode
+        interval_enc = pack("<h", interval_ms)
+        hci_set_adv_params = ["0x08", "0x0006"]
+        hci_set_adv_params += self._bytes_to_strarray(interval_enc)
+        hci_set_adv_params += self._bytes_to_strarray(interval_enc)
+        hci_set_adv_params += ["03", "00", "00", "00", "00", "00", "00", "00", "00"]
+        hci_set_adv_params += ["07", "00"]
+        self._run_hci_cmd(hci_set_adv_params)
+
+        # Start BLE advertising
+        self._run_hci_cmd(["0x08", "0x000a"] + ["01"], wait=0)
diff --git a/main.py b/main.py
index 94e2c6a..cc0f23f 100644
--- a/main.py
+++ b/main.py
@@ -1,7 +1,9 @@
 from time import sleep
+import yaml
 import smbus2
 import si7201
 import tmp006
+import hci
 
 bus = smbus2.SMBus(1)  # set up I2C bus 1
 
@@ -20,7 +22,16 @@ print(irtempsensor.manID)  # read the manufacturer ID and print
 print(irtempsensor.devID)  # read the device ID and print
 print(irtempsensor.temperature)  # read the temperature and print
 
-print("========= TMP006 Test Loop =========")
+print("========= Testing HCI Cast =========")
+with open(".secrets.yml", "r") as secrets:
+    try:
+        secrets = yaml.safe_load(secrets)
+        key = secrets["key"]  # Get Base64 encoded device public key from secrets file
+    except yaml.YAMLError as exc:
+        print(exc)
+
+btcast = hci.HCIBroadcaster(key)  # set up HCI Broadcaster
+btcast.start_advertising(5000)  # start advertising with interval of 5 seconds
+
 while True:
-    print(irtempsensor.temperature)  # read the temperature and print
-    sleep(1)  # wait for 1 second
+    btcast.start_advertising(5000)  # start advertising with interval of 5 seconds
diff --git a/requirements.txt b/requirements.txt
index c3ea966..bf38714 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
 colorzero==2.0
 gpiozero==1.6.2
+PyYAML==6.0
 smbus2==0.4.1