Serialport Support

- allow communication to elm327 device via a serialport
- allow creation of elm327 device without requiring unwrap()
- added some extra documentation
- expose reset() functionality of device
- serial_comm and ftdi_comm abstractions added

src/device/serialport_comm.rs

@@ -0,0 +1,46 @@
+use super::serial_comm::{SerialComm, DEFAULT_BAUD_RATE};
+use super::Result;
+use std::io::{Read, Write};
+use std::time::Duration;
+
+/// 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)?)
+    }
+}