Additional cleanup

src/obd2_device.rs

@@ -0,0 +1,208 @@
+use core::fmt;
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// A higher-level API for using an OBD-II device
+pub trait Obd2Device {
+    /// Send an OBD-II command with mode and PID and get responses
+    ///
+    /// The responses are a list with one element for each ECU that responds. The data is decoded
+    /// into the ODB-II bytes from the vehicle and the first two bytes of the
+    /// response---representing the mode and PID the vehicle received---are validated and removed.
+    fn obd_command(&mut self, mode: u8, pid: u8) -> Result<Vec<Vec<u8>>>;
+
+    /// Send an OBD-II command with only mode and get responses
+    ///
+    /// The responses are a list with one element for each ECU that responds. The data is decoded
+    /// into the ODB-II bytes from the vehicle and the first byte of the response---representing
+    /// the mode the vehicle recieved---is validated and removed.
+    fn obd_mode_command(&mut self, mode: u8) -> Result<Vec<Vec<u8>>>;
+
+    /// Send command and get list of OBD-II responses as an array
+    ///
+    /// Like [obd_command](Self::obd_command), but each ECU's response (after removing the first
+    /// two bytes) is converted to an array of the specified length. If any response is the wrong
+    /// length, and error is returned.
+    ///
+    /// This function can be used when the response length is known, so that it is easier to index
+    /// into the response without causing a panic and without dealing with Options.
+    fn obd_command_len<const RESPONSE_LENGTH: usize>(
+        &mut self,
+        mode: u8,
+        pid: u8,
+    ) -> Result<Vec<[u8; RESPONSE_LENGTH]>> {
+        self.obd_command(mode, pid)?
+            .into_iter()
+            .map(|v| {
+                let l = v.len();
+                v.try_into()
+                    .map_err(|_| Error::IncorrectResponseLength("length", RESPONSE_LENGTH, l))
+            })
+            .collect()
+    }
+
+    /// Send command and get array of OBD-II responses with each as an array
+    ///
+    /// Like [obd_command_len](Self::obd_command_len), but also convert the list of ECU responses
+    /// to an array. This can be used when the number of ECUs that should respond is known in
+    /// advance. Most commonly, this will be when the count of ECUs is one, for values where only a
+    /// single ECU should respond like the speed of the vehicle.
+    fn obd_command_cnt_len<const RESPONSE_COUNT: usize, const RESPONSE_LENGTH: usize>(
+        &mut self,
+        mode: u8,
+        pid: u8,
+    ) -> Result<[[u8; RESPONSE_LENGTH]; RESPONSE_COUNT]> {
+        let result = self.obd_command_len::<RESPONSE_LENGTH>(mode, pid)?;
+        let count = result.len();
+        result
+            .try_into()
+            .map_err(|_| Error::IncorrectResponseLength("count", RESPONSE_COUNT, count))
+    }
+
+    /// Retreive the VIN (vehicle identification number)
+    ///
+    /// This should match the number printed on the vehicle, and is a good command for checking
+    /// that the OBD-II interface is working correctly.
+    fn get_vin(&mut self) -> Result<String> {
+        let mut result = self.obd_command(0x09, 0x02)?.pop().unwrap();
+        result.remove(0); // do not know what this byte is
+        Ok(String::from_utf8(result)?)
+    }
+
+    /// Get DTC (diagnostic trouble code) metadata for each ECU
+    fn get_dtc_info(&mut self) -> Result<Vec<DtcsInfo>> {
+        let result = self.obd_command(0x01, 0x01)?;
+
+        result
+            .iter()
+            .map(|response| {
+                if response.len() == 4 {
+                    Ok(DtcsInfo {
+                        malfunction_indicator_light: (response[0] & 0x80) == 0x80,
+                        dtc_count: response[0] & 0x7f,
+                        common_test_availability: ((response[1] & 0xf0) >> 1)
+                            | (response[1] & 0x07),
+                        is_compression_engine: (response[1] & 0x08) == 0x08,
+                        specific_test_availability: ((response[3] as u16) << 8)
+                            | (response[2] as u16),
+                    })
+                } else {
+                    Err(Error::Other(format!(
+                        "get_dtc_info: expected length 4, got {}",
+                        response.len()
+                    )))
+                }
+            })
+            .collect()
+    }
+
+    /// Get DTCs for each ECU
+    fn get_dtcs(&mut self) -> Result<Vec<Vec<Dtc>>> {
+        let result = self.obd_mode_command(0x03)?;
+        result
+            .iter()
+            .map(|response| match response.first() {
+                Some(0) => {
+                    if response.len() % 2 == 1 {
+                        let mut ret = Vec::new();
+                        for i in (1..response.len()).step_by(2) {
+                            ret.push(match response[i] >> 6 {
+                                0 => Dtc::Powertrain(0),
+                                1 => Dtc::Chassis(0),
+                                2 => Dtc::Body(0),
+                                3 => Dtc::Network(0),
+                                _ => unreachable!(),
+                            });
+                        }
+                        Ok(ret)
+                    } else {
+                        Err(Error::Other(format!(
+                            "invalid response when getting DTCs {:?}",
+                            response
+                        )))
+                    }
+                }
+                Some(n) if *n <= 3 => todo!(),
+                Some(_) => Err(Error::Other(format!(
+                    "invalid response {:?} when getting DTCs",
+                    response
+                ))),
+                None => Err(Error::Other(
+                    "no response bytes when getting DTCs".to_owned(),
+                )),
+            })
+            .collect::<Result<Vec<Vec<Dtc>>>>()
+    }
+
+    /// Get the RPM in increments of 0.25
+    fn get_rpm(&mut self) -> Result<f32> {
+        let result = self.obd_command_cnt_len::<1, 2>(0x01, 0x0C)?[0];
+        Ok(f32::from(u16::from_be_bytes(result)) / 4.0)
+    }
+
+    /// Get the speed in km/h
+    fn get_speed(&mut self) -> Result<u8> {
+        Ok(self.obd_command_cnt_len::<1, 1>(0x01, 0x0C)?[0][0])
+    }
+}
+
+#[allow(dead_code)]
+#[derive(Debug)]
+pub struct DtcsInfo {
+    malfunction_indicator_light: bool,
+    dtc_count: u8,
+    common_test_availability: u8,
+    is_compression_engine: bool,
+    specific_test_availability: u16,
+}
+
+#[derive(Debug)]
+pub enum Dtc {
+    Powertrain(u16),
+    Chassis(u16),
+    Body(u16),
+    Network(u16),
+}
+
+impl fmt::Display for Dtc {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let (c, n) = match self {
+            Self::Powertrain(n) => ('P', n),
+            Self::Chassis(n) => ('C', n),
+            Self::Body(n) => ('B', n),
+            Self::Network(n) => ('U', n),
+        };
+        f.write_fmt(format_args!("{}{:03X}", c, n))
+    }
+}
+
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("Device error: `{0:?}`")]
+    Device(DeviceError),
+    #[error("Other OBD2 error: `{0}`")]
+    Other(String),
+    #[error("Incorrect length (`{0}`): expected `{1}`, got `{2}`")]
+    IncorrectResponseLength(&'static str, usize, usize),
+}
+
+#[derive(Debug)]
+pub struct DeviceError(super::device::Error);
+
+impl From<super::device::Error> for Error {
+    fn from(e: super::device::Error) -> Self {
+        Error::Device(DeviceError(e))
+    }
+}
+
+impl From<std::num::ParseIntError> for Error {
+    fn from(e: std::num::ParseIntError) -> Self {
+        Error::Other(format!("invalid data recieved: {:?}", e))
+    }
+}
+
+impl From<std::string::FromUtf8Error> for Error {
+    fn from(e: std::string::FromUtf8Error) -> Self {
+        Error::Other(format!("invalid string recieved: {:?}", e))
+    }
+}