ELM327: initial code

The middleware can provide an easy way to access ELM327.
This commit add a class for ELM327 OBD-II adapter over a serial connection (e.g
/dev/ttyUSB0). This is not a CAN bus sniffer. The ELM327 abstracts raw CAN data
and provides access only to specific OBD-II parameters. It is designed for
querying diagnostic information from the vehicle's ECU.

Signed-off-by: Douglas Schilling Landgraf <dlandgra@redhat.com>

src/elm327/elm327.py

@@ -0,0 +1,273 @@
+# 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.
+
+import serial
+import time
+
+
+class ELM327:
+    """
+    A class to interact with an ELM327 OBD-II adapter over a serial connection.
+
+    This is not a CAN bus sniffer. The ELM327 abstracts raw CAN data
+    and provides access only to specific OBD-II parameters. It is designed for
+    querying diagnostic information from the vehicle's ECU.
+
+    Attributes:
+        port (str): The serial port where the ELM327 device is connected (e.g., `/dev/ttyUSB0`).
+        baudrate (int): The baud rate for the serial communication (usually 38400 for ELM327).
+        timeout (int or float): The timeout for reading responses from the ELM327.
+        ser (serial.Serial): The serial connection to the ELM327 device.
+    """
+
+    # Protocol commands
+    PROTOCOL_CAN = b'ATSP6\r'  # ISO 15765-4 CAN (11-bit ID, 500 kbps)
+    PROTOCOL_ISO_9141 = b'ATSP3\r'  # ISO 9141-2
+    PROTOCOL_KWP2000 = b'ATSP4\r'  # ISO 14230-4 KWP (5 baud init)
+    PROTOCOL_KWP2000_FAST = b'ATSP5\r'  # ISO 14230-4 KWP (fast init)
+    PROTOCOL_J1850_PWM = b'ATSP1\r'  # SAE J1850 PWM (Ford)
+    PROTOCOL_J1850_VPW = b'ATSP2\r'  # SAE J1850 VPW (GM)
+    PROTOCOL_CAN_29BIT = b'ATSP7\r'  # ISO 15765-4 CAN (29-bit ID, 250 kbps)
+    PROTOCOL_AUTO = b'ATSP0\r'  # Automatic protocol detection
+
+    # General commands
+    RESET_COMMAND = b'ATZ\r'  # Reset the ELM327 device
+    SHOW_HEADERS_COMMAND = b'ATH1\r'  # Show CAN message headers
+    SUPPORTED_PIDS_COMMAND = b'0100\r'  # Request supported PIDs
+    RPM_COMMAND = b'010C\r'  # Request engine RPM
+    SPEED_COMMAND = b'010D\r'  # Request vehicle speed
+    FUEL_LEVEL_COMMAND = b'012F\r'  # Request fuel level
+    CLEAR_DTC_COMMAND = b'04\r'  # Clear diagnostic trouble codes (DTCs)
+    CHECK_DTC_COMMAND = b'03\r'  # Check for diagnostic trouble codes (DTCs)
+    VIN_COMMAND = b'0902\r'  # Request VIN
+    BATTERY_VOLTAGE_COMMAND = b'ATRV\r'  # Request battery voltage
+    THROTTLE_POSITION_COMMAND = b'0111\r'  # Request throttle position
+    COOLANT_TEMP_COMMAND = b'0105\r'  # Request coolant temperature
+    AIR_INTAKE_TEMP_COMMAND = b'010F\r'  # Request air intake temperature
+    FUEL_PRESSURE_COMMAND = b'010A\r'  # Request fuel pressure
+    FUEL_SYSTEM_STATUS_COMMAND = b'0103\r'  # Request fuel system status
+    FUEL_CONSUMPTION_COMMAND = b'015E\r'  # Request fuel consumption
+    ENGINE_LOAD_COMMAND = b'0104\r'  # Request engine load
+
+    def __init__(self, port='/dev/ttyUSB0', baudrate=38400, timeout=1):
+        """
+        Initialize the ELM327 object and open the serial connection.
+
+        Args:
+            port (str): The serial port where the ELM327 device is connected (default `/dev/ttyUSB0`).
+            baudrate (int): The baud rate for the serial connection (default 38400).
+            timeout (int or float): The timeout duration for reading responses (default 1 second).
+        """
+        self.port = port
+        self.baudrate = baudrate
+        self.timeout = timeout
+        self.ser = serial.Serial(port=self.port, baudrate=self.baudrate, timeout=self.timeout)
+
+    def reset(self):
+        """
+        Reset the ELM327 device by sending the ATZ command.
+
+        Returns:
+            str: The response from the ELM327 device after the reset command.
+        """
+        self.ser.write(self.RESET_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def show_headers(self):
+        """
+        Enable displaying CAN message headers by sending the ATH1 command.
+
+        Returns:
+            str: The response from the ELM327 device after enabling headers.
+        """
+        self.ser.write(self.SHOW_HEADERS_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_can(self):
+        self.ser.write(self.PROTOCOL_CAN)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_iso_9141(self):
+        self.ser.write(self.PROTOCOL_ISO_9141)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_kwp2000(self):
+        self.ser.write(self.PROTOCOL_KWP2000)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_kwp2000_fast(self):
+        self.ser.write(self.PROTOCOL_KWP2000_FAST)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_j1850_pwm(self):
+        self.ser.write(self.PROTOCOL_J1850_PWM)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_j1850_vpw(self):
+        self.ser.write(self.PROTOCOL_J1850_VPW)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_can_29bit(self):
+        self.ser.write(self.PROTOCOL_CAN_29BIT)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def set_protocol_auto(self):
+        self.ser.write(self.PROTOCOL_AUTO)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_supported_pids(self):
+        self.ser.write(self.SUPPORTED_PIDS_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_rpm(self):
+        self.ser.write(self.RPM_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_speed(self):
+        self.ser.write(self.SPEED_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_fuel_level(self):
+        self.ser.write(self.FUEL_LEVEL_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def clear_dtc(self):
+        self.ser.write(self.CLEAR_DTC_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def check_dtc(self):
+        self.ser.write(self.CHECK_DTC_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_vin(self):
+        """
+        Request the Vehicle Identification Number (VIN) by sending the 0902 command.
+
+        Returns:
+            str: The VIN as reported by the vehicle's ECU.
+        """
+        self.ser.write(self.VIN_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_battery_voltage(self):
+        """
+        Request the battery voltage by sending the ATRV command.
+
+        Returns:
+            str: The battery voltage as reported by the ELM327 device.
+        """
+        self.ser.write(self.BATTERY_VOLTAGE_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_throttle_position(self):
+        """
+        Request the throttle position by sending the 0111 command.
+
+        Returns:
+            str: The throttle position as a percentage.
+        """
+        self.ser.write(self.THROTTLE_POSITION_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_coolant_temperature(self):
+        """
+        Request the engine coolant temperature by sending the 0105 command.
+
+        Returns:
+            str: The engine coolant temperature in degrees Celsius.
+        """
+        self.ser.write(self.COOLANT_TEMP_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_air_intake_temperature(self):
+        """
+        Request the air intake temperature by sending the 010F command.
+
+        Returns:
+            str: The air intake temperature in degrees Celsius.
+        """
+        self.ser.write(self.AIR_INTAKE_TEMP_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_fuel_pressure(self):
+        """
+        Request the fuel pressure by sending the 010A command.
+
+        Returns:
+            str: The fuel pressure as reported by the ECU.
+        """
+        self.ser.write(self.FUEL_PRESSURE_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_fuel_system_status(self):
+        """
+        Request the fuel system status by sending the 0103 command.
+
+        Returns:
+            str: The fuel system status as reported by the ECU.
+        """
+        self.ser.write(self.FUEL_SYSTEM_STATUS_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_fuel_consumption(self):
+        """
+        Request the real-time fuel consumption rate by sending the 015E command.
+
+        Returns:
+            str: The fuel consumption rate as reported by the ECU.
+        """
+        self.ser.write(self.FUEL_CONSUMPTION_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def get_engine_load(self):
+        """
+        Request the engine load by sending the 0104 command.
+
+        Returns:
+            str: The engine load as reported by the ECU.
+        """
+        self.ser.write(self.ENGINE_LOAD_COMMAND)
+        time.sleep(1)
+        return self.ser.read(128).decode('utf-8')
+
+    def close(self):
+        """
+        Close the serial connection to the ELM327 device.
+
+        Returns:
+            None
+        """
+        self.ser.close()