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Documentation and organization improvements

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This commit is contained in:
Robert Sammelson 2023-05-15 00:56:36 -04:00
parent 2a43bf94bd
commit 1b4ccd0dde
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GPG key ID: 92F1F04EDB06B9E9
5 changed files with 131 additions and 49 deletions
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99
src/device/elm327.rs
View file

@ -7,6 +7,12 @@ use std::{
use super::{Error, Obd2BaseDevice, Obd2Reader, Result};
/// An ELM327 OBD-II adapter
///
/// It communicates with the computer over 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.
pub struct Elm327 {
device: ftdi::Device,
buffer: VecDeque<u8>,
@ -28,23 +34,16 @@ impl Obd2BaseDevice for Elm327 {
Ok(())
}
fn flush(&mut self) -> Result<()> {
thread::sleep(time::Duration::from_millis(500));
self.read_into_queue()?;
self.buffer.clear();
thread::sleep(time::Duration::from_millis(500));
Ok(())
}
fn send_serial_cmd(&mut self, data: &str) -> Result<()> {
self.device.write_all(data.as_bytes())?;
fn send_cmd(&mut self, data: &[u8]) -> Result<()> {
self.device.write_all(data)?;
self.device.write_all(b"\r\n")?;
// thread::sleep(time::Duration::from_millis(200));
let line = self.get_line()?;
if line.as_ref().is_some_and(|v| v == data.as_bytes()) {
if line.as_ref().is_some_and(|v| v == data) {
Ok(())
} else {
Err(Error::Communication(format!(
"send_serial_cmd: got {:?} instead of echoed command ({})",
"send_serial_cmd: got {:?} instead of echoed command ({:?})",
line, data
)))
}
@ -56,7 +55,13 @@ impl Obd2Reader for Elm327 {
self.get_until(b'\n', false)
}
fn get_until_prompt(&mut self) -> Result<Option<Vec<u8>>> {
/// Read data until the ELM327's prompt character is printed
///
/// This will recieve the entire OBD-II response. The prompt signifies that the ELM327 is ready
/// for another command. If this is not called after each OBD-II command is sent, the prompt
/// character will come out of the recieve queue later and because it is not valid hex this
/// could cause problems. If a timeout occurs, `Ok(None)` will be returned.
fn get_response(&mut self) -> Result<Option<Vec<u8>>> {
self.get_until(b'>', true)
}
}
@ -85,6 +90,20 @@ impl Elm327 {
Ok(device)
}
/// Flush the device's buffer
pub fn flush(&mut self) -> Result<()> {
thread::sleep(time::Duration::from_millis(500));
self.read_into_queue()?;
self.buffer.clear();
thread::sleep(time::Duration::from_millis(500));
Ok(())
}
fn flush_buffers(&mut self) -> Result<()> {
self.device.usb_purge_buffers()?;
Ok(())
}
fn connect(&mut self, check_baud_rate: bool) -> Result<()> {
self.flush_buffers()?;
thread::sleep(time::Duration::from_millis(500));
@ -108,7 +127,7 @@ impl Elm327 {
self.send_serial_cmd("ATZ")?;
debug!(
"reset_ic: got response {:?}",
self.get_until_prompt()?
self.get_response()?
.as_ref()
.map(|l| std::str::from_utf8(l.as_slice()))
);
@ -117,8 +136,14 @@ impl Elm327 {
fn reset_protocol(&mut self) -> Result<()> {
info!("Performing protocol reset");
debug!("reset_protocol: got response {:?}", self.cmd("ATSP0")?);
debug!("reset_protocol: got OBD response {:?}", self.cmd("0100")?);
debug!(
"reset_protocol: got response {:?}",
self.serial_cmd("ATSP0")?
);
debug!(
"reset_protocol: got OBD response {:?}",
self.cmd(&[0x01, 0x00])?
);
self.flush_buffers()?;
Ok(())
}
@ -148,7 +173,7 @@ impl Elm327 {
// our TX is bad
self.device.set_baud_rate(self.baud_rate)?;
debug!("Baud rate bad - device did not receive response");
self.get_until_prompt()?;
self.get_response()?;
}
} else {
// reset baud rate and keep looking
@ -160,11 +185,11 @@ impl Elm327 {
.as_ref()
.map(|r| String::from_utf8_lossy(r))
);
self.get_until_prompt()?;
self.get_response()?;
}
} else {
debug!("Baud rate bad - did not ok initially");
self.get_until_prompt()?;
self.get_response()?;
}
thread::sleep(time::Duration::from_millis(200));
@ -222,25 +247,16 @@ impl Elm327 {
}
fn get_byte(&mut self) -> Result<Option<u8>> {
self.read_into_queue()?;
loop {
let b = self.buffer.pop_front();
if b != Some(b'\0') {
return Ok(b);
match self.buffer.pop_front() {
Some(b'\0') => Ok(None),
Some(b) => Ok(Some(b)),
None => {
self.read_into_queue()?;
Ok(None)
}
}
}
fn flush_buffers(&mut self) -> Result<()> {
self.device.usb_purge_buffers()?;
Ok(())
}
fn send_serial_str(&mut self, data: &str) -> Result<()> {
self.device.write_all(data.as_bytes())?;
Ok(())
}
fn read_into_queue(&mut self) -> Result<()> {
let mut buf = [0u8; 16];
loop {
@ -258,4 +274,19 @@ impl Elm327 {
}
Ok(())
}
fn send_serial_cmd(&mut self, data: &str) -> Result<()> {
self.send_cmd(data.as_bytes())
}
fn serial_cmd(&mut self, cmd: &str) -> Result<Option<String>> {
self.send_serial_cmd(cmd)?;
self.get_response()
.map(|o| o.and_then(|resp| String::from_utf8(resp).ok()))
}
fn send_serial_str(&mut self, data: &str) -> Result<()> {
self.device.write_all(data.as_bytes())?;
Ok(())
}
}

39
src/device/mod.rs
View file

@ -3,22 +3,49 @@ pub use elm327::Elm327;
type Result<T> = std::result::Result<T, Error>;
/// A lower-level API for using an OBD-II device
pub trait Obd2BaseDevice: Obd2Reader {
/// Reset the device and the OBD-II interface
///
/// First the device is reset, if it is stateful. Then the OBD-II interface is reinitialized,
/// which resets the selected protocol on the device and rechecks the vehicle manufacturer if
/// needed.
fn reset(&mut self) -> Result<()>;
fn flush(&mut self) -> Result<()>;
fn send_serial_cmd(&mut self, data: &str) -> Result<()>;
fn cmd(&mut self, cmd: &str) -> Result<Option<String>> {
self.send_serial_cmd(cmd)?;
self.get_until_prompt()
/// Send an OBD-II command
fn send_cmd(&mut self, data: &[u8]) -> Result<()>;
/// Send an OBD-II command and get the reply
///
/// The reply is decoded into a String of mostly hex data. Depending on the format of the
/// response, some other characters may be included like line numbers for multiline responses
/// (of the format "0: AB CD ...").
fn cmd(&mut self, cmd: &[u8]) -> Result<Option<String>> {
self.send_cmd(cmd)?;
self.get_response()
.map(|o| o.and_then(|resp| String::from_utf8(resp).ok()))
}
}
/// An API for reading OBD-II response data
pub trait Obd2Reader {
/// Try to get a single line of data from the device
///
/// The trailing newline is not included. This function will never return an empty line, it
/// will retry until a line with data is found. If no data is available after a reasonable
/// timeout, `Ok(None)` will be returned.
fn get_line(&mut self) -> Result<Option<Vec<u8>>>;
fn get_until_prompt(&mut self) -> Result<Option<Vec<u8>>>;
/// Get an entire OBD-II response
///
/// Empty vectors are allowed to be returned. This function should always be called after a
/// command is sent, possibly after calling [get_line](Self::get_line) to read the first lines,
/// so that any metadata sent by the device after the response from the vehicle can be dealt
/// with.
fn get_response(&mut self) -> Result<Option<Vec<u8>>>;
}
/// Error type for low-level ODB-II communication issues
#[derive(thiserror::Error, Debug)]
pub enum Error {
#[error("FTDI error: `{0:?}`")]