Add more doc comments

src/device/elm327.rs

@@ -13,6 +13,9 @@ use super::{Error, Obd2BaseDevice, Obd2Reader, Result};
 /// 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,
     buffer: VecDeque<u8>,

src/device/mod.rs

@@ -50,10 +50,15 @@ pub trait Obd2Reader {
 /// Error type for low-level ODB-II communication issues
 #[derive(thiserror::Error, Debug)]
 pub enum Error {
+    /// An error with the underlying [FTDI device](ftdi::Device)
     #[error("FTDI error: `{0:?}`")]
     Ftdi(ftdi::Error),
+
+    /// An I/O error in a low-level [std::io] stream operation
     #[error("IO error: `{0:?}`")]
     IO(std::io::Error),
+
+    /// An OBD-II or interface device protocol error
     #[error("Communication error: `{0}`")]
     Communication(String),
 }