Various changes

- allow communication to elm327 device via a serialport
- allow creation of elm327 device without requiring unwrap()
- added some extra documentation
- add fuel_level obd-ii command
- expose reset() functionality of device

src/commands/mod.rs

@@ -220,4 +220,7 @@ func! {
 
     /// Get service 1 PID support for $21 to $40
     fn get_service_1_pid_support_2(0x01, 0x20) -> u32;
+
+    // Get the fuel level (out of 255)
+    fn get_fuel_level(0x01, 0x2F) -> u8;
 }

src/device/elm327.rs

@@ -1,38 +1,24 @@
 use log::{debug, info, trace};
-use std::{
-    collections::VecDeque,
-    io::{Read, Write},
-    thread, time,
-};
+use std::{collections::VecDeque, thread, time};
 
-use super::{Error, Obd2BaseDevice, Obd2Reader, Result};
+use super::{serial_comm::SerialComm, Error, Obd2BaseDevice, Obd2Reader, Result};
 
 /// An ELM327 OBD-II adapter
 ///
-/// It communicates with the computer over UART using an FTDI FT232R USB-to-UART converter.
+/// It communicates with the computer or UART using an FTDI FT232R USB-to-UART converter.
 /// Commands to the device itself are indicated by sending "AT" followed by the command, while
 /// plain strings of hex data indicate OBD-II requests to be sent to the vehicle. The responses of
 /// the vehicle are echoed back as hex characters. Capitalization and spaces are always ignored.
 ///
 /// [Datasheet for v1.4b](https://github.com/rsammelson/obd2/blob/master/docs/ELM327DSH.pdf), and
 /// the [source](https://www.elmelectronics.com/products/dsheets/).
-pub struct Elm327 {
-    device: ftdi::Device,
+pub struct Elm327<T: SerialComm> {
+    device: T,
     buffer: VecDeque<u8>,
     baud_rate: u32,
 }
 
-impl Default for Elm327 {
-    /// Create a Elm327 device
-    ///
-    /// # Panics
-    /// If the device cannot be initialized. Use [Self::new] for a panic-free API.
-    fn default() -> Self {
-        Elm327::new().unwrap()
-    }
-}
-
-impl Obd2BaseDevice for Elm327 {
+impl<T: SerialComm> Obd2BaseDevice for Elm327<T> {
     fn reset(&mut self) -> Result<()> {
         self.flush_buffers()?;
         self.reset_ic()?;
@@ -52,7 +38,7 @@ impl Obd2BaseDevice for Elm327 {
     }
 }
 
-impl Obd2Reader for Elm327 {
+impl<T: SerialComm> Obd2Reader for Elm327<T> {
     fn get_line(&mut self) -> Result<Option<Vec<u8>>> {
         self.get_until(b'\n', false)
     }
@@ -68,22 +54,14 @@ impl Obd2Reader for Elm327 {
     }
 }
 
-impl Elm327 {
-    fn new() -> Result<Self> {
-        let mut ftdi_device = ftdi::find_by_vid_pid(0x0403, 0x6001)
-            .interface(ftdi::Interface::A)
-            .open()?;
-
-        ftdi_device.set_baud_rate(38400)?;
-        ftdi_device.configure(ftdi::Bits::Eight, ftdi::StopBits::One, ftdi::Parity::None)?;
-        // device.set_latency_timer(2).unwrap();
-
-        ftdi_device.usb_reset()?;
-
+impl<T: SerialComm> Elm327<T> {
+    /// Creates a new Elm327 adapter with the given
+    /// unserlying Serial Communication device
+    pub fn new(serial_device: T) -> Result<Self> {
         let mut device = Elm327 {
-            device: ftdi_device,
+            device: serial_device,
             buffer: VecDeque::new(),
-            baud_rate: 38400,
+            baud_rate: 38_400,
         };
 
         device.connect(false)?;
@@ -102,7 +80,7 @@ impl Elm327 {
     }
 
     fn flush_buffers(&mut self) -> Result<()> {
-        self.device.usb_purge_buffers()?;
+        self.device.purge_buffers()?;
         Ok(())
     }
 
@@ -127,11 +105,10 @@ impl Elm327 {
     fn reset_ic(&mut self) -> Result<()> {
         info!("Performing IC reset");
         self.send_serial_str("ATZ")?;
+        let response = self.get_response()?;
         debug!(
             "reset_ic: got response {:?}",
-            self.get_response()?
-                .as_ref()
-                .map(|l| std::str::from_utf8(l.as_slice()))
+            response.as_ref().map(|l| std::str::from_utf8(l.as_slice()))
         );
         Ok(())
     }
@@ -140,16 +117,12 @@ impl Elm327 {
         info!("Performing protocol reset");
 
         // set to use automatic protocol selection
-        debug!(
-            "reset_protocol: got response {:?}",
-            self.serial_cmd("ATSP0")?
-        );
+        let elm_response = self.serial_cmd("ATSP0")?;
+        debug!("reset_protocol: got response {:?}", elm_response);
 
-        // perform the search
-        debug!(
-            "reset_protocol: got OBD response {:?}",
-            self.cmd(&[0x01, 0x00])?
-        );
+        // perform the search for ECUs
+        let obd_response = self.cmd(&[0x01, 0x00])?;
+        debug!("reset_protocol: got OBD response {:?}", obd_response);
 
         // get rid of extra data hanging around in the buffer
         self.flush_buffers()?;
@@ -269,13 +242,18 @@ impl Elm327 {
     fn read_into_queue(&mut self) -> Result<()> {
         let mut buf = [0u8; 16];
         loop {
-            let len = self.device.read(&mut buf)?;
-            if len > 0 {
-                self.buffer.extend(&buf[0..len]);
-                trace!(
-                    "read_into_queue: values {:?}",
-                    std::str::from_utf8(&buf[0..len])
-                );
+            let len_res = self.device.read(&mut buf);
+            if let Ok(len) = len_res {
+                if len > 0 {
+                    self.buffer.extend(&buf[0..len]);
+                    trace!(
+                        "read_into_queue: values {:?}",
+                        std::str::from_utf8(&buf[0..len])
+                    );
+                } else {
+                    trace!("read_into_queue: no values left to read");
+                    break;
+                }
             } else {
                 trace!("read_into_queue: no values left to read");
                 break;

src/device/mod.rs

@@ -3,6 +3,9 @@
 mod elm327;
 pub use elm327::Elm327;
 
+mod serial_comm;
+pub use serial_comm::{FTDIDevice, SerialPort};
+
 type Result<T> = std::result::Result<T, Error>;
 
 /// A lower-level API for using an OBD-II device
@@ -54,6 +57,10 @@ pub enum Error {
     #[error("FTDI error: `{0:?}`")]
     Ftdi(ftdi::Error),
 
+    /// An error with the underlying [serialport device](serialport::SerialPort)
+    #[error("Serialport error: `{0:?}`")]
+    Serialport(serialport::Error),
+
     /// An I/O error in a low-level [std::io] stream operation
     #[error("IO error: `{0:?}`")]
     IO(std::io::Error),
@@ -69,6 +76,12 @@ impl From<ftdi::Error> for Error {
     }
 }
 
+impl From<serialport::Error> for Error {
+    fn from(e: serialport::Error) -> Self {
+        Error::Serialport(e)
+    }
+}
+
 impl From<std::io::Error> for Error {
     fn from(e: std::io::Error) -> Self {
         Error::IO(e)

src/device/serial_comm.rs

@@ -0,0 +1,94 @@
+use super::Result;
+use std::io::{Read, Write};
+use std::time::Duration;
+
+const DEFAULT_BAUD_RATE: u32 = 38_400;
+
+/// An API to communicate with a serial device
+pub trait SerialComm {
+    fn write_all(&mut self, data: &[u8]) -> Result<()>;
+    fn read(&mut self, data: &mut [u8]) -> Result<usize>;
+    fn set_baud_rate(&mut self, baud_rate: u32) -> Result<()>;
+    fn purge_buffers(&mut self) -> Result<()>;
+}
+
+/// Communicate with a serial device using the
+/// serialport library
+///
+/// /dev/tty* or similar on unix-like systems
+/// COM devices on Windows systems
+pub struct SerialPort {
+    device: Box<dyn serialport::SerialPort>,
+}
+
+impl SerialPort {
+    /// Creates a new instance of a SerialPort
+    pub fn new(path: &str) -> Result<Self> {
+        let device = serialport::new(path, DEFAULT_BAUD_RATE)
+            .timeout(Duration::from_millis(10))
+            .parity(serialport::Parity::None)
+            .data_bits(serialport::DataBits::Eight)
+            .stop_bits(serialport::StopBits::One)
+            .path(path)
+            .open()?;
+
+        Ok(Self { device })
+    }
+}
+
+impl SerialComm for SerialPort {
+    fn write_all(&mut self, data: &[u8]) -> Result<()> {
+        Ok(self.device.write_all(data)?)
+    }
+
+    fn read(&mut self, data: &mut [u8]) -> Result<usize> {
+        Ok(self.device.read(data)?)
+    }
+
+    fn set_baud_rate(&mut self, baud_rate: u32) -> Result<()> {
+        Ok(self.device.set_baud_rate(baud_rate)?)
+    }
+
+    fn purge_buffers(&mut self) -> Result<()> {
+        Ok(self.device.clear(serialport::ClearBuffer::All)?)
+    }
+}
+
+/// Communicate with a USB to Serial FTDI device
+/// with the FTDI library
+pub struct FTDIDevice {
+    device: ftdi::Device,
+}
+
+impl FTDIDevice {
+    /// Creates a new instance of an FTDIDevice
+    pub fn new() -> Result<Self> {
+        let mut device = ftdi::find_by_vid_pid(0x0404, 0x6001)
+            .interface(ftdi::Interface::A)
+            .open()?;
+
+        device.set_baud_rate(DEFAULT_BAUD_RATE)?;
+        device.configure(ftdi::Bits::Eight, ftdi::StopBits::One, ftdi::Parity::None)?;
+        device.usb_reset()?;
+
+        Ok(Self { device })
+    }
+}
+
+impl SerialComm for FTDIDevice {
+    fn write_all(&mut self, data: &[u8]) -> Result<()> {
+        Ok(self.device.write_all(data)?)
+    }
+
+    fn read(&mut self, data: &mut [u8]) -> Result<usize> {
+        Ok(self.device.read(data)?)
+    }
+
+    fn set_baud_rate(&mut self, baud_rate: u32) -> Result<()> {
+        Ok(self.device.set_baud_rate(baud_rate)?)
+    }
+
+    fn purge_buffers(&mut self) -> Result<()> {
+        Ok(self.device.usb_purge_buffers()?)
+    }
+}

src/error.rs

@@ -1,3 +1,6 @@
+//! Error types for OBD-II related errors
+
+/// Result type defaulted with this library's error type
 pub type Result<T> = std::result::Result<T, Error>;
 
 /// An error with OBD-II communication
@@ -16,8 +19,9 @@ pub enum Error {
     Other(String),
 }
 
+/// An error with the ELM327 device
 #[derive(Debug)]
-pub struct DeviceError(crate::device::Error);
+pub struct DeviceError(pub crate::device::Error);
 
 impl From<super::device::Error> for Error {
     fn from(e: super::device::Error) -> Self {

src/interface.rs

@@ -6,7 +6,6 @@ use super::{device::Obd2BaseDevice, Error, Obd2Device, Result};
 ///
 /// Wraps an implementer of [Obd2BaseDevice] to allow for higher-level usage of the OBD-II
 /// interface.
-#[derive(Default)]
 pub struct Obd2<T: Obd2BaseDevice> {
     device: T,
 }
@@ -43,6 +42,18 @@ impl<T: Obd2BaseDevice> Obd2Device for Obd2<T> {
 }
 
 impl<T: Obd2BaseDevice> Obd2<T> {
+    /// Creates a new instance of an Obd device
+    pub fn new(dev: T) -> Result<Self> {
+        let device = Obd2 { device: dev };
+
+        Ok(device)
+    }
+
+    /// Resets the device
+    pub fn reset(&mut self) -> Result<()> {
+        Ok(self.device.reset()?)
+    }
+
     fn command(&mut self, command: &[u8]) -> Result<Vec<Vec<u8>>> {
         let response = self
             .device

src/lib.rs

@@ -6,14 +6,20 @@
 //!
 //! # Usage
 //! ```
-//! use obd2::{commands::Obd2DataRetrieval, device::Elm327, Obd2};
+//! use obd2::{commands::Obd2DataRetrieval, device::{Elm327, FTDIDevice}, Obd2};
 //!
 //! fn main() -> Result<(), obd2::Error> {
-//!     let mut device = Obd2::<Elm327>::default();
+//!     let mut device = Obd2::<Elm327::<FTDIDevice>>::new(Elm327::new(FTDIDevice::new()?)?)?;
 //!     println!("VIN: {}", device.get_vin()?);
 //!     Ok(())
 //! }
 //! ```
+//!
+//! alternatively, you could use a serial port provided by your operating system such as
+//! /dev/ttyUSB0 on unix-like systems
+//! ```
+//! let mut device = Obd2::<Elm327::<SerialPort>>::new(Elm327::new(SerialPort::new("/dev/ttyUSB0")?)?)?;
+//! ```
 
 #![forbid(unsafe_code)]
 #![warn(missing_docs, clippy::panic)]
@@ -22,7 +28,7 @@ pub mod commands;
 
 pub mod device;
 
-mod error;
+pub mod error;
 pub use error::Error;
 use error::Result;