feat: add xl9535 support, issue #400 (#403)

* feat: add xl9535 support, issue #400

README.md

@@ -27,6 +27,7 @@ Hardware support is provided by specific GPIO, Sensor and Stream modules. It's e
   - PCF8575 IO expander (`pcf8575`)
   - PiFace Digital IO 2 (`piface2`)
   - Raspberry Pi GPIO (`raspberrypi`)
+  - XL9535/PCA9535/TCA9535 IO expander (`xl9535`)
 
 ### Sensors
 

mqtt_io/modules/gpio/xl9535.py

@@ -0,0 +1,82 @@
+"""
+XL9535/PCA9535/TCA9535 IO expander
+"""
+
+from typing import Optional, cast
+
+from ...exceptions import RuntimeConfigError
+from ...types import ConfigType, PinType
+from . import GenericGPIO, PinDirection, PinPUD
+
+REQUIREMENTS = ("smbus2",)
+CONFIG_SCHEMA = {
+    "i2c_bus_num": {"type": "integer", "required": True, "empty": False},
+    "chip_addr": {"type": "integer", "required": True, "empty": False},
+}
+
+#XL9535_INPUT_PORT_0 = 0x00,
+#XL9535_INPUT_PORT_1 = 0x01
+XL9535_OUTPUT_PORT_0 = 0x02
+#XL9535_OUTPUT_PORT_1 = 0x03
+#XL9535_INVERSION_PORT_0 = 0x04
+#XL9535_INVERSION_PORT_1 = 0x05
+XL9535_CONFIG_PORT_0 = 0x06
+#XL9535_CONFIG_PORT_1 = 0x07
+
+class GPIO(GenericGPIO):
+    """
+    Implementation of GPIO class for the XL9535/PCA9535/TCA9535 IO expander chip.
+
+    Pin numbers 0 - 15.
+    """
+
+    PIN_SCHEMA = {
+        "pin": {"type": 'integer', "required": True, "min": 0, "max": 15},
+    }
+
+    def setup_module(self) -> None:
+        # pylint: disable=import-outside-toplevel,import-error
+        # pylint: disable=no-name-in-module
+        from smbus2 import SMBus  # type: ignore
+
+        self.bus = SMBus(self.config["i2c_bus_num"])
+        self.address = self.config["chip_addr"]
+
+        # configure all pins as outputs
+        self.bus.write_word_data(self.address, XL9535_CONFIG_PORT_0, 0x0000)
+        # off all outputs be default
+        self.bus.write_word_data(self.address, XL9535_OUTPUT_PORT_0, 0x0000)
+
+    def setup_pin(
+        self,
+        pin: PinType,
+        direction: PinDirection,
+        pullup: PinPUD,
+        pin_config: ConfigType,
+        initial: Optional[str] = None,
+    ) -> None:
+        # I han't found any ready-made expansion boards on sale where the chip works as an input.
+        # For simplicity, the implementation only supports the chip working in output mode.
+        if direction == PinDirection.INPUT:
+            raise RuntimeConfigError("Unsupported PinDirection: INPUT")
+        initial = pin_config.get("initial")
+        if initial is not None:
+            if initial == "high":
+                self.set_pin(pin, True)
+            elif initial == "low":
+                self.set_pin(pin, False)
+
+    def set_pin(self, pin: PinType, value: bool) -> None:
+        assert pin in range(16), "Pin number must be an integer between 0 and 15"
+        current_state = self.bus.read_word_data(self.address, XL9535_OUTPUT_PORT_0)
+        bit = 1 << cast(int, pin)
+        new_state = current_state | bit if value else current_state & (~bit & 0xffff)
+        self.bus.write_word_data(self.address, XL9535_OUTPUT_PORT_0, new_state)
+
+    def get_pin(self, pin: PinType) -> bool:
+        assert pin in range(16), "Pin number must be an integer between 0 and 15"
+        state = self.bus.read_word_data(self.address, XL9535_OUTPUT_PORT_0)
+        return bool(state & 1 << cast(int, pin))
+
+    def cleanup(self) -> None:
+        self.bus.close()