/// <summary>
/// Creates an instance of the ELM327 driver.
/// </summary>
/// <param name="serialPortName">The name of the serial port the ELM is connected to
/// ("COM1", "COM2", etc.).</param>
/// <param name="protocolType">The desired OBD protocol to use. Using
/// <see cref="Elm327.Core.ElmDriver.ElmObdProtocolType.Automatic"/> is usually a good idea.</param>
/// <param name="measuringUnit">The desired unit type for reporting readings.</param>
public ElmDriver(
string serialPortName,
ElmObdProtocolType protocolType,
ElmMeasuringUnitType measuringUnit)
{
this.MeasuringUnitType = measuringUnit;
this.ElmVersionID = string.Empty;
this.ObdMode01 = new ObdGenericMode01(this);
this.ObdMode09 = new ObdGenericMode09(this);
this.protocolType = protocolType;
this.receiveBuffer = new byte[ElmDriver.RECEIVE_BUFFER_SIZE];
this.serialPort = new SerialPort(
serialPortName,
ElmDriver.BAUD_RATE,
Parity.None,
8,
StopBits.One);
this.serialPort.ErrorReceived += new SerialErrorReceivedEventHandler(ElmDriver.uart_ErrorReceived);
}
/// <summary>
/// Attempts to open a connection to the ELM chip.
/// </summary>
/// <returns>A value indicating the result of the connection attempt.</returns>
public ElmConnectionResultType Connect()
{
// Try to force the connection closed if it is open and the caller wants to
// reinitialize
lock (this.serialPort)
{
if (this.serialPort.IsOpen)
{
// TODO: This is untested
try
{
this.serialPort.Close();
}
catch (Exception ex)
{
Util.Log(ex);
}
}
}
// Try to open the COM port
lock (this.serialPort)
{
try
{
this.serialPort.Open();
this.serialPort.Flush();
this.serialPort.DiscardInBuffer();
this.serialPort.DiscardOutBuffer();
}
catch (Exception ex)
{
Util.Log(ex);
return(ElmConnectionResultType.NoConnectionToElm);
}
}
// Perform a reset on the ELM. If we get a null back from this call,
// it means we're unable to see it (probably a wiring issue).
if (this.SendAndReceiveMessage("ATZ") == null)
{
return(ElmConnectionResultType.NoConnectionToElm);
}
// Turn line feeds and echo off, turn on space printing (as our code currently
// expects it) and retrieve the ELM's version information
// TODO: ELM responses will be faster if we turn off space printing, but leaving
// as-is for now to enable easy message parsing
this.SendAndReceiveMessage("ATL0");
this.SendAndReceiveMessage("ATE0");
this.SendAndReceiveMessage("ATS1");
this.ElmVersionID = this.SendAndReceiveMessage("ATI");
// Set the caller's desired protocol, then make a simple "0100" call to
// make sure the ECU responds. If we get anything back other than something
// that starts with "41 00", it means the ELM can't talk to the OBD
// system.
this.ProtocolType = this.protocolType;
string response = this.SendAndReceiveMessage("0100");
if (response == null || response.IndexOf("41 00") != 0)
{
return(ElmConnectionResultType.NoConnectionToObd);
}
// Ask the ELM to give us the protocol it's using. We need to ask for
// this value in case the user chose the "Automatic" setting for protocol
// type, so we'll know which protocol was actually selected by the ELM.
response = this.SendAndReceiveMessage("ATDPN");
if (response != null && response.Length > 0)
{
try
{
// 'A' will be the first character returned if the user chose
// automatic search mode
if (response[0] == 'A' && response.Length > 1)
{
this.protocolType = (ElmObdProtocolType)response[1];
}
else
{
this.protocolType = (ElmObdProtocolType)response[0];
}
}
catch (Exception ex)
{
Util.Log(ex);
}
}
return(ElmConnectionResultType.Connected);
}