elmobd

# -*- org-confirm-babel-evaluate: nil -*-

* README

[[file:https://img.shields.io/badge/status-active-green.svg]]
[[https://travis-ci.org/rzetterberg/elmobd][file:https://travis-ci.org/rzetterberg/elmobd.svg?branch=master]]
[[https://goreportcard.com/report/github.com/rzetterberg/elmobd][file:https://goreportcard.com/badge/github.com/rzetterberg/elmobd?status.svg]]
[[https://godoc.org/github.com/rzetterberg/elmobd][file:https://godoc.org/github.com/rzetterberg/elmobd?status.svg]]

#+NAME: version_output
#+begin_src emacs-lisp :results raw :exports results
(with-temp-buffer
  (insert-file-contents "./VERSION")
  (format "- Version :: %s" (buffer-string))))
#+end_src

#+RESULTS: version_output
- Version :: 0.7.0

Go library for communicating with cars [[https://en.wikipedia.org/wiki/On-board_diagnostics][OBD-II]] system using [[https://www.elmelectronics.com/ic/elm327/][ELM327]] based
USB-devices.

To make this library as good as possible - feedback, bug reports and feature
requests are very welcome in the GitHub issues of this project.

** How it works

There are more than 10 different OBD-II signal protocol variations used by the
various cars that exist. To avoid having to handle all the details of these
protocols the ELM327 exists. The ELM327 acts a [[https://en.wikipedia.org/wiki/Facade_pattern][facade]] between the computer and
the car. You talk to the ELM327 using a simple text based protocol similar to
the [[https://en.wikipedia.org/wiki/Hayes_command_set][Hayes command set]] and the ELM327 takes care of the communication details
of the car.

#+LATEX: \vspace{0.5cm}
#+LATEX: \begin{center}
#+ATTR_LATEX: :width 8cm
#+RESULTS: fig:overview
[[file:docs/assets/overview-diagram.png]]
#+LATEX: \end{center}

As shown in the diagram above this library connects to a serial device of the
operating system. The library is not concerned with what is connected to that
serial device, whether it's a bluetooth USB-dongle with a ELM327 at the other
end or a ELM327 connected directly via an USB-cable.

Communicating with the ELM327 is similar to communicating with a web server.
You make a *request* and wait for a *response*. However, in this context we are
*calling a command* and waiting for *one or more responses*.

This library is designed to be used in a way that resembles the way you
physically use the device. You have a type called ~Device~ that represents
a ELM327 device connected to the computer. This ~Device~ then has a function
called ~RunCommand~ that sends a command to the actual device and then waits
for a response.

This library aims to be as type safe as possible, which means that you don't
deal with raw text commands, instead you have different command /types/.

All command /types/ need to implement the ~OBDCommand~ /interface/ to be
able to be run on the device. Since there are A LOT of OBD commands, you can
easily extend this library, by just implementing the ~OBDCommand~ /interface/
of your commands.

Let's start by looking at some example of how you use the library.

** Example usage

*Note:* these examples are performed on Linux. If you are using another platform
there should be minimal changes, but they are not documented yet. Go ahead
and put a :+1: on issue #11 if you think this should be prioritized.

First of all, you need to plug in your ELM327 device into your computer and
get the path to the device. You can plugin the device and check dmesg, this is
what I get on my computer:

#+BEGIN_EXAMPLE
$ dmesg | tail
[359720.858480] usb 6-2: Manufacturer: FTDI
[359720.858482] usb 6-2: SerialNumber: A503GJEX
[359720.897717] usbcore: registered new interface driver usbserial
[359720.897733] usbcore: registered new interface driver usbserial_generic
[359720.897748] usbserial: USB Serial support registered for generic
[359720.901755] usbcore: registered new interface driver ftdi_sio
[359720.901767] usbserial: USB Serial support registered for FTDI USB Serial Device
[359720.901839] ftdi_sio 6-2:1.0: FTDI USB Serial Device converter detected
[359720.901913] usb 6-2: Detected FT232RL
[359720.904481] usb 6-2: FTDI USB Serial Device converter now attached to ttyUSB0
#+END_EXAMPLE

Now that I know that the device is available at ~/dev/ttyUSB0~ I can use the
library to connect to the device and check the ~ELM327~ version of the device:

*example1.go*
#+NAME: src:example1
#+BEGIN_SRC go :tangle ./examples/example_1/main.go :mkdirp yes
package main

import (
	"flag"
	"fmt"
	"github.com/rzetterberg/elmobd"
)

func main() {
	serialPath := flag.String(
		"serial",
		"/dev/ttyUSB0",
		"Path to the serial device to use",
	)

	flag.Parse()

	dev, err := elmobd.NewTestDevice(*serialPath, false)

	if err != nil {
		fmt.Println("Failed to create new device", err)
		return
	}

	version, err := dev.GetVersion()

	if err != nil {
		fmt.Println("Failed to get version", err)
		return
	}

	fmt.Println("Device has version", version)
}
#+END_SRC

*Note:* These examples uses the function ~NewTestDevice~, which uses a mocked
ELM327 device. To use a real ELM327 device, you instead use ~NewDevice~. The
reason why a mocked device is used is because the examples should be runnable
without using a real device.

#+BEGIN_EXAMPLE
$ go run example.go
Device has version OBDII by elm329@gmail.com
#+END_EXAMPLE

The next step is to run some OBD commands on the device. For this we need to
plug in the ELM327 into our car and turn on the ignition.

Like mentioned before you use the function ~RunCommand~ that accepts a
~OBDCommand~ to run. A ~OBDCommand~ has 3 responsibilities:

- Tell the ELM327 what command to run
- Store the value
- Convert the value to a common format

So you start out by creating a new ~OBDCommand~ that does not contain a value.
You then take that ~OBDCommand~ and call the ~RunCommand~ function with it.
~RunCommand~ will then return the ~OBDCommand~ with the value from the car.

Let's try this out by checking the RPM of the engine. There is a ~OBDCommand~
for that defined in the library already, called ~EngineRPM~. We start by
creating a new ~EngineRPM~ that we call ~RunCommand~ with:

*example2.go*
#+NAME: src:example2
#+BEGIN_SRC go :tangle ./examples/example_2/main.go :mkdirp yes
package main

import (
	"flag"
	"fmt"
	"github.com/rzetterberg/elmobd"
)

func main() {
	serialPath := flag.String(
		"serial",
		"/dev/ttyUSB0",
		"Path to the serial device to use",
	)

	flag.Parse()

	dev, err := elmobd.NewTestDevice(*serialPath, false)

	if err != nil {
		fmt.Println("Failed to create new device", err)
		return
	}

	rpm, err := dev.RunOBDCommand(elmobd.NewEngineRPM())

	if err != nil {
		fmt.Println("Failed to get rpm", err)
		return
	}

	fmt.Printf("Engine spins at %s RPMs\n", rpm.ValueAsLit())
}
#+END_SRC

There are more than 180 different OBD commands, and cars have different support
for these commands. So to avoid sending OBD commands to the car that it does not
support we can check what commands the car support:

*example3.go*
#+NAME: src:example3
#+BEGIN_SRC go :tangle ./examples/example_3/main.go :mkdirp yes
package main

import (
	"flag"
	"fmt"
	"github.com/rzetterberg/elmobd"
)

func main() {
	serialPath := flag.String(
		"serial",
		"/dev/ttyUSB0",
		"Path to the serial device to use",
	)

	flag.Parse()

	dev, err := elmobd.NewTestDevice(*serialPath, false)

	if err != nil {
		fmt.Println("Failed to create new device", err)
		return
	}

	supported, err := dev.CheckSupportedCommands()

	if err != nil {
		fmt.Println("Failed to check supported commands", err)
		return
	}

	rpm := elmobd.NewEngineRPM()

	if supported.IsSupported(rpm) {
		fmt.Println("The car supports checking RPM")
	} else {
		fmt.Println("The car does NOT supports checking RPM")
	}
}
#+END_SRC

The ~supported~ here is a ~SupportedCommands~ which is a special type that
stores the raw lookup table and exposes two helper functions that reads this
table:

- ~IsSupported~ :: Check if given command is supported
- ~FilterSupported~ :: Filters out supported commands from given list

For simplicity there's a function called ~GetSensorCommands~ which gives you a
list of all the commands defined in the library. You can use this list of
commands and filter out what commands are supported on by car:

*example4.go*
#+NAME: src:example4
#+BEGIN_SRC go :tangle ./examples/example_4/main.go :mkdirp yes
package main

import (
	"flag"
	"fmt"
	"github.com/rzetterberg/elmobd"
)

func main() {
	serialPath := flag.String(
		"serial",
		"/dev/ttyUSB0",
		"Path to the serial device to use",
	)

	flag.Parse()

	dev, err := elmobd.NewTestDevice(*serialPath, false)

	if err != nil {
		fmt.Println("Failed to create new device", err)
		return
	}

	supported, err := dev.CheckSupportedCommands()

	if err != nil {
		fmt.Println("Failed to check supported commands", err)
		return
	}

	allCommands := elmobd.GetSensorCommands()
	carCommands := supported.FilterSupported(allCommands)

	fmt.Printf("%d of %d commands supported:\n", len(carCommands), len(allCommands))

	for _, cmd := range carCommands {
		fmt.Printf("- %s supported\n", cmd.Key())
	}
}
#+END_SRC

Besides checking sensor values, you can also check whether the [[https://en.wikipedia.org/wiki/Check_engine_light][MIL]] is on and if there are
any [[https://en.wikipedia.org/wiki/On-board_diagnostics#EOBD_fault_codes][DTCs]]:

*example5.go*
#+NAME: src:example5
#+BEGIN_SRC go :tangle ./examples/example_5/main.go :mkdirp yes
package main

import (
	"flag"
	"fmt"
	"github.com/rzetterberg/elmobd"
)

func main() {
	serialPath := flag.String(
		"serial",
		"/dev/ttyUSB0",
		"Path to the serial device to use",
	)

	flag.Parse()

	dev, err := elmobd.NewTestDevice(*serialPath, false)

	if err != nil {
		fmt.Println("Failed to create new device", err)
		return
	}

	cmd, err := dev.RunOBDCommand(elmobd.NewMonitorStatus())

	if err != nil {
		fmt.Println("Failed to get monitor status", err)
		return
	}

        status := cmd.(*elmobd.MonitorStatus)

	fmt.Printf("MIL is on: %t, DTCamount: %d\n", status.MilActive, status.DtcAmount)
}
#+END_SRC

Please see [[https://godoc.org/github.com/rzetterberg/elmobd][the godocs]] for a more detailed explanation of the library and it's
structure.

** Features

- [X] Reading sensor data
- [ ] Reading trouble codes
- [ ] Resetting Check Engine Light
- [ ] Reading freezed sensor data

** Roadmap

The project uses quarterly milestones to plan upcoming changes. The current
quarter will focus on implementing new features. To see the details of what
will be done see the milestone [[https://github.com/rzetterberg/elmobd/milestone/4][2018 Q3]].

Changes of the library are tracked in the [[file:CHANGELOG.md][CHANGELOG]].

** Compability

*** Platforms

The library has been built and tested on the following platforms:

| Operating system    | Go version |
|---------------------+------------|
| Linux 4.9.25 x86_64 | 1.9        |

*** Cars

The library has been used successfully on the following cars:

| Car                       | Library version | Tester       |
|---------------------------+-----------------+--------------|
| Lexus IS200 Manual 2004   |           0.3.0 | @rzetterberg |
| Ford Ka 2011              |           0.5.0 | @Enrico204   |
| Ford Transit Automat 2019 |			0.6.0 | @mikspec	 |