From f6cb0258e7e0027073a3cbcf76f23a2ad64e5bc6 Mon Sep 17 00:00:00 2001
From: Steffen Klee <steffen.klee@gmail.com>
Date: Wed, 10 Apr 2024 23:52:37 +0200
Subject: [PATCH 1/3] feat: add MH-Z19 sensor module

This adds support for NDIR CO2 sensor MH-Z19. The sensor module supports
reading CO2 ppm value and configuring the ppm range over the UART/serial
interface.
---
 mqtt_io/modules/sensor/mhz19.py | 61 +++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 mqtt_io/modules/sensor/mhz19.py

diff --git a/mqtt_io/modules/sensor/mhz19.py b/mqtt_io/modules/sensor/mhz19.py
new file mode 100644
index 00000000..1ce73831
--- /dev/null
+++ b/mqtt_io/modules/sensor/mhz19.py
@@ -0,0 +1,61 @@
+"""
+MH-Z19 NDIR CO2 sensor
+"""
+
+from mqtt_io.modules.sensor import GenericSensor
+from mqtt_io.types import CerberusSchemaType, ConfigType, SensorValueType
+
+REQUIREMENTS = ("pyserial",)
+CONFIG_SCHEMA: CerberusSchemaType = {
+    "device": dict(type="string", required=True, empty=False),
+    "range": dict(type="integer", required=False, empty=False, default=5000, allowed=[2000, 5000, 10000]),
+}
+
+class Sensor(GenericSensor):
+    """
+    Implementation of Sensor class for the MH-Z19 CO2 sensor using UART/serial.
+    """
+
+    @staticmethod
+    def _calc_checksum(data: bytes) -> bytes:
+        v = sum(data[1:]) % 0x100
+        v = (0xff - v + 1) % 0x100
+        return v.to_bytes(1, "big")
+
+    @staticmethod
+    def _check_checksum(data: bytes) -> bool:
+        return Sensor._calc_checksum(data[:-1]) == data[-1:]
+
+    @staticmethod
+    def _add_checksum(data: bytes) -> bytes:
+        return data + Sensor._calc_checksum(data)
+
+    def setup_module(self) -> None:
+        # pylint: disable=import-error,import-outside-toplevel
+        import serial  # type: ignore
+
+        self.ser = serial.Serial(
+            port=self.config["device"],
+            baudrate=9600,
+            bytesize=serial.EIGHTBITS,
+            parity=serial.PARITY_NONE,
+            stopbits=serial.STOPBITS_ONE,
+        )
+
+        # setup detection range
+        cmd = Sensor._add_checksum(b"\xff\x01\x99\x00\x00\x00" + self.config["range"].to_bytes(2, "big"))
+        self.ser.write(cmd)
+        # no response
+
+    def cleanup(self) -> None:
+        self.ser.close()
+
+    def get_value(self, sens_conf: ConfigType) -> SensorValueType:
+        self.ser.write(Sensor._add_checksum(b"\xff\x01\x86\x00\x00\x00\x00\x00"))
+        resp = self.ser.read(9)
+
+        if len(resp) == 9:
+            if resp[0:2] == b"\xff\x86" and Sensor._check_checksum(resp):
+                return int.from_bytes(resp[2:4], "big")
+
+        return None

From 2bfb30d2d08d171b77bf592f03842a162d323cfe Mon Sep 17 00:00:00 2001
From: Steffen Klee <steffen.klee@gmail.com>
Date: Fri, 28 Jun 2024 21:47:13 +0200
Subject: [PATCH 2/3] doc: add MH-Z19 sensor example configuration

---
 config.example.yml | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/config.example.yml b/config.example.yml
index 5ead074e..b23e37e2 100644
--- a/config.example.yml
+++ b/config.example.yml
@@ -34,6 +34,11 @@ sensor_modules:
     type: DS18S20
     address: 000803702e49
 
+  - name: mhz19
+    module: mhz19
+    device: "/dev/ttyS1"
+    range: 5000
+
 digital_inputs:
   - name: button
     module: raspberrypi
@@ -76,3 +81,10 @@ sensor_inputs:
     module: ds18b22
     interval: 10
     digits: 2
+
+  - name: co2_mhz19
+    module: mhz19
+    interval: 30
+    ha_discovery:
+      name: CO2 MH-Z19
+      device_class: carbon_dioxide

From 0f6fe5a0a135fd5ba45aca2efe3d107978a42bbd Mon Sep 17 00:00:00 2001
From: Steffen Klee <steffen.klee@gmail.com>
Date: Thu, 4 Jul 2024 00:52:22 +0200
Subject: [PATCH 3/3] fix: linting mhz19

---
 mqtt_io/modules/sensor/mhz19.py | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/mqtt_io/modules/sensor/mhz19.py b/mqtt_io/modules/sensor/mhz19.py
index 1ce73831..04f30ead 100644
--- a/mqtt_io/modules/sensor/mhz19.py
+++ b/mqtt_io/modules/sensor/mhz19.py
@@ -8,7 +8,8 @@
 REQUIREMENTS = ("pyserial",)
 CONFIG_SCHEMA: CerberusSchemaType = {
     "device": dict(type="string", required=True, empty=False),
-    "range": dict(type="integer", required=False, empty=False, default=5000, allowed=[2000, 5000, 10000]),
+    "range": dict(type="integer", required=False, empty=False, default=5000,
+                  allowed=[2000, 5000, 10000]),
 }
 
 class Sensor(GenericSensor):
@@ -18,9 +19,9 @@ class Sensor(GenericSensor):
 
     @staticmethod
     def _calc_checksum(data: bytes) -> bytes:
-        v = sum(data[1:]) % 0x100
-        v = (0xff - v + 1) % 0x100
-        return v.to_bytes(1, "big")
+        value = sum(data[1:]) % 0x100
+        value = (0xff - value + 1) % 0x100
+        return value.to_bytes(1, "big")
 
     @staticmethod
     def _check_checksum(data: bytes) -> bool:
@@ -43,7 +44,8 @@ def setup_module(self) -> None:
         )
 
         # setup detection range
-        cmd = Sensor._add_checksum(b"\xff\x01\x99\x00\x00\x00" + self.config["range"].to_bytes(2, "big"))
+        cmd = Sensor._add_checksum(b"\xff\x01\x99\x00\x00\x00" +
+                                   self.config["range"].to_bytes(2, "big"))
         self.ser.write(cmd)
         # no response