MIL_status_example (PowerBroker2#201)

* Added example program to check MIL (Check Engine Light) status and number of current DTC codes.

examples/ESP32_Check_MIL/ESP32_Check_MIL.ino

@@ -0,0 +1,79 @@
+#include "ELMduino.h"
+#include <BluetoothSerial.h>
+
+#define ELM_PORT SerialBT
+#define DEBUG_PORT Serial
+
+typedef enum
+{   MILSTATUS,
+    DTCCODES
+} dtc_states;
+
+BluetoothSerial SerialBT;
+ELM327 myELM327;
+dtc_states dtc_state = MILSTATUS;
+uint8_t numCodes = 0;
+uint8_t milStatus =0;
+
+// This example program demonstrates how to use ELMduino to check the MIL (Check Engine Light)
+// status and the number of current DTC codes that are present. 
+
+void setup()
+{
+    DEBUG_PORT.begin(115200);
+    ELM_PORT.begin("ArduHUD", true);
+    ELM_PORT.setPin("1234");
+
+    DEBUG_PORT.println("Starting connection...");
+    if (!ELM_PORT.connect("ELMULATOR"))
+    {
+        DEBUG_PORT.println("Couldn't connect to ELM327 - Phase 1");
+        while (1)
+            ;
+    }
+
+    if (!myELM327.begin(ELM_PORT))
+    {
+        DEBUG_PORT.println("ELM327 Couldn't connect to ECU - Phase 2");
+        while (1)
+            ;
+    }
+
+    DEBUG_PORT.println("Connected to ELM327");
+
+}
+
+void loop()
+{
+    myELM327.monitorStatus(); // Gets the number of current DTC codes present
+
+    if (myELM327.nb_rx_state == ELM_SUCCESS)
+    {            
+        // We are only interested in the third byte of the response that
+        // encodes the MIL status and number of codes present
+        milStatus = (myELM327.responseByte_2 & 0x80);
+        numCodes = (myELM327.responseByte_2 - 0x80);
+
+        DEBUG_PORT.print("MIL (Check Engine Light) is: ");
+        if (milStatus)
+        {
+            DEBUG_PORT.println("ON.");
+        }
+        else
+        {
+            DEBUG_PORT.println("OFF.");
+        }
+
+        DEBUG_PORT.print("Number of codes present: ");
+        DEBUG_PORT.println(numCodes);
+
+        DEBUG_PORT.println("Checking again in 10 seconds.\n\n");
+        delay(10000);   // Wait 10 seconds before we query again.
+    }
+    else if (myELM327.nb_rx_state != ELM_GETTING_MSG)
+    {
+        myELM327.printError();
+        DEBUG_PORT.println("Trying again in 10 seconds.\n\n");
+        delay(10000);
+    }
+}