[Issue #4] - Adding support for sht4x sensors, configurable via the SENSOR_TYPE parameter

config.example.py

@@ -12,3 +12,6 @@ MQTT_PASS = "mqtt_password"  # MQTT password (leave blank for no login)
 NODE_NAME = "Room Weather"  # Name that's displayed on HA Device Card
 NODE_ID = "room_env"  # Unique slug for entity_id and MQTT topic path
 CLIENT_ID = f"pico2w_{NODE_ID}"  # Unique client ID used by the MQTT broker
+
+# Sensor selection: "bme280" or "sht41"
+SENSOR_TYPE = "bme280"

main.py

@@ -15,8 +15,8 @@ except ImportError:
     while True:
         time.sleep(2)
 
-# Default NODE_NAME to NODE_ID if not explicitly provided in config.py
 NODE_NAME = getattr(Config, "NODE_NAME", Config.NODE_ID)
+SENSOR_TYPE = getattr(Config, "SENSOR_TYPE", "bme280").lower()
 STATE_TOPIC = f"homeassistant/sensor/{Config.NODE_ID}/state"
 
 
@@ -35,19 +35,16 @@ class SimpleMQTT:
         self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         self.sock.connect(addr)
 
-        # Flags: Clean session (bit 1) + optional credentials
         flags = 0x02
         if username:
             flags |= 0x80
         if password:
             flags |= 0x40
 
-        # Variable header: Protocol Name (MQTT) + Level (4) + Flags + KeepAlive (60s)
         var_header = bytearray(
             [0x00, 0x04, ord("M"), ord("Q"), ord("T"), ord("T"), 0x04, flags, 0x00, 0x3C]
         )
 
-        # Payload
         payload = bytearray()
         payload.extend(self._encode_str(client_id))
         if username:
@@ -59,7 +56,6 @@ class SimpleMQTT:
         packet = bytearray([0x10]) + self._encode_len(len(body)) + body
         self.sock.write(packet)
 
-        # Read CONNACK (4 bytes: 0x20, 0x02, ack_flags, return_code)
         resp = self.sock.read(4)
         if not resp or resp[0] != 0x20 or resp[3] != 0x00:
             code = resp[3] if resp and len(resp) >= 4 else "nil"
@@ -202,16 +198,53 @@ class BME280:
         }
 
 
+# -------------------------------------------------------------
+# SHT41 Driver (I2C)
+# -------------------------------------------------------------
+class SHT41:
+    DEFAULT_ADDR = 0x44
+    CMD_MEASURE_HIGH_PRECISION = 0xFD
+
+    def __init__(self, i2c, addr=DEFAULT_ADDR):
+        self.i2c = i2c
+        self.addr = addr
+        # Soft reset
+        self.i2c.writeto(self.addr, b"\x94")
+        time.sleep(0.01)
+
+    def read_values(self):
+        # Trigger high precision measurement
+        self.i2c.writeto(self.addr, bytes([self.CMD_MEASURE_HIGH_PRECISION]))
+        # Conversion takes up to 8.2ms
+        time.sleep(0.01)
+
+        # 6 bytes: [Temp_MSB, Temp_LSB, CRC, Hum_MSB, Hum_LSB, CRC]
+        data = self.i2c.readfrom(self.addr, 6)
+
+        raw_t = (data[0] << 8) | data[1]
+        raw_h = (data[3] << 8) | data[4]
+
+        # Official Sensirion conversion equations
+        temp = -45.0 + 175.0 * (raw_t / 65535.0)
+        hum = -6.0 + 125.0 * (raw_h / 65535.0)
+        hum = max(0.0, min(hum, 100.0))
+
+        return {
+            "temperature": round(temp, 2),
+            "humidity": round(hum, 2),
+            "pressure": None,
+        }
+
+
 # -------------------------------------------------------------
 # Home Assistant MQTT Discovery
 # -------------------------------------------------------------
-def register_ha_discovery(mqtt):
-    # Device naming uses NODE_NAME so each board has its own clean device card in HA
+def register_ha_discovery(mqtt, sensor_type):
     device_info = (
         f'"device":{{'
         f'"identifiers":["{Config.NODE_ID}"],'
         f'"name":"{NODE_NAME}",'
-        f'"model":"Pico 2 W",'
+        f'"model":"Pico 2 W ({sensor_type.upper()})",'
         f'"manufacturer":"Raspberry Pi"'
         f"}}"
     )
@@ -231,15 +264,20 @@ def register_ha_discovery(mqtt):
             "cls": "humidity",
             "val_tpl": "{{ value_json.humidity }}",
         },
-        {
-            "id": "pressure",
-            "name": "Pressure",
-            "unit": "hPa",
-            "cls": "atmospheric_pressure",
-            "val_tpl": "{{ value_json.pressure }}",
-        },
     ]
 
+    # Only register atmospheric pressure if the sensor provides it
+    if sensor_type == "bme280":
+        configs.append(
+            {
+                "id": "pressure",
+                "name": "Pressure",
+                "unit": "hPa",
+                "cls": "atmospheric_pressure",
+                "val_tpl": "{{ value_json.pressure }}",
+            }
+        )
+
     for c in configs:
         topic = f"homeassistant/sensor/{Config.NODE_ID}/{c['id']}/config"
         unique_id = f"{Config.NODE_ID}_{c['id']}"
@@ -281,7 +319,6 @@ def connect_wifi():
 # Panic when the sensor isn't ready
 # -------------------------------------------------------------
 def panic(err=None):
-    """Signals a fatal fault by blinking the onboard LED continuously."""
     if err:
         print(f"Fatal error: {err}")
     led = Pin("LED", Pin.OUT)
@@ -294,9 +331,17 @@ def panic(err=None):
 # Main Execution Loop
 # -------------------------------------------------------------
 def main():
-    # Adjust SDA/SCL pins according to your wiring
-    i2c = SoftI2C(sda=Pin(16), scl=Pin(17), freq=100000)
-    bme = BME280(i2c)
+    i2c = SoftI2C(sda=Pin(4), scl=Pin(5), freq=100000)
+
+    # Initialize selected sensor
+    if SENSOR_TYPE == "sht41":
+        print("Using SHT41 sensor (0x44)")
+        sensor = SHT41(i2c)
+    elif SENSOR_TYPE == "bme280":
+        print("Using BME280 sensor (0x77)")
+        sensor = BME280(i2c)
+    else:
+        raise ValueError(f"Unsupported SENSOR_TYPE '{SENSOR_TYPE}'. Use 'bme280' or 'sht41'.")
 
     connect_wifi()
 
@@ -310,18 +355,27 @@ def main():
     print("MQTT connected.")
 
     # Publish discovery retained messages
-    register_ha_discovery(mqtt)
+    register_ha_discovery(mqtt, SENSOR_TYPE)
 
     # Telemetry loop
     interval = getattr(Config, "UPDATE_INTERVAL", 30)
     while True:
         try:
-            data = bme.read_values()
-            state_json = (
-                f'{{"temperature":{data["temperature"]},'
-                f'"humidity":{data["humidity"]},'
-                f'"pressure":{data["pressure"]}}}'
-            )
+            data = sensor.read_values()
+
+            # Format payload conditionally based on available readings
+            if data.get("pressure") is not None:
+                state_json = (
+                    f'{{"temperature":{data["temperature"]},'
+                    f'"humidity":{data["humidity"]},'
+                    f'"pressure":{data["pressure"]}}}'
+                )
+            else:
+                state_json = (
+                    f'{{"temperature":{data["temperature"]},'
+                    f'"humidity":{data["humidity"]}}}'
+                )
+
             mqtt.publish(STATE_TOPIC, state_json)
             print(f"[{NODE_NAME}] Published: {state_json}")
         except Exception as e:
@@ -338,10 +392,7 @@ def main():
 
 
 if __name__ == "__main__":
-    # Allow 3.3V power rails and I2C registers to settle on cold boot
     time.sleep(2)
-
-    # Indicate startup has begun
     Pin("LED", Pin.OUT).on()
 
     try: