Hack an ELM327 Cable to Make an Arduino OBD2 Scann

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Hack an ELM327 Cable to make an Arduino OBD2 Scanner by mviljoen2 mviljoen2 on on October 10, 2014

Table of Contents Hack an ELM327 Cable to make an Arduino OBD2 Scanner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Intro: Hack an ELM327 ELM327 Cable to make make an Arduino OBD2 Scanner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Step 1: Prepare the ELM327 ELM327 board to bypass the USB USB bridge chip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Step 2: Attach the Arduino LCD Shield to the arduino . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Step 3: Hooking it up to your vehicle, vehicle, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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http://www.instructables.com/id/Hack-an-ELM327-Cable-to-make-an-Arduino-OBD2-Scann/

Intro: Hack an ELM327 Cable to make an Arduino OBD2 Scanner In my previous instructable i created an OBD2 Simulator so that i didn't have to test my Arduino OBD2 Reader in the car the whole time but instead in the comfort of my own home. Stuff you need. Arduino UNO LCD shield ELM327 USB cable. What it can read Coolant Temp,IAT Temp,Ambient Temp, Throttle %,RPM,Vehicle Speed, Air flow Rate,Barometric Pressure I will be removing the board from the ELM327 Enclosure and then bypass the USB bridge chip and attach the Serial TX/RX pins of the arduino to the Serial TX/RX pins onto the ELM327 board, program the arduino and attach the ELM327 OBD2 connector to the OBD2 port . Pretty Simple


Step 1: Prepare the ELM327 board to bypass the USB bridge chip Start by removing the sticker on ELM327 Cable's Enclosure, remove the 4 screws with a smallish star screwdriver. And then take out the board. Tip:Borrow your Girlfrien's/Wife's cutex and make a mark on one side of the connector that runs to the OBD2 Connector, that way when you take it out you will know which side it goes because it can go in both ways, for this instructable its not needed to remove the mentioned connector though. Solder 2 wires to the TX and RX pins on the board, in the attached photo's i have included the pin-out information of the USB Bridge chip. Be careful though I managed to de-solder some components which i could not put back, but luckily it still worked afterwards. Tip:Program the arduino so that it writes to the serial monitor with some short delays in between, then connect a jumper cable to the TX pin of the arduino and poke around with the other end on the board to see where you get some serial activity, the surface mounted LED's wil flicker as communication happens, unfortunately this will not work for the RX side but in the pictures its easy enough to see where I soldered it onto the board. NOTE:The USB cable is connected to the board with a 4 pin connector, i cut the middle 2 out so that the ELM327 cannot communicate with the PC whilst its connected, this way it only gets power from my PC's USB port and the serial controller on the board will not be occupied by the PC allowing the Arduino to talk to it Once done put it back into the box, I just taped it up because In my Jeep the box is in my way and cannot drive it whilst in the driver seat, I will be using the enclosure for something else.


Step 2: Attach the Arduino LCD Shield to the arduino Attach the Arduino LCD Shield to the arduino and hook it up to your PC to be programmed. Below is my Arduino Sketch, I noticed that the formatting messes with the code a bit, I have some more information available related to this build you can also view the code here. http://techtinker.co.za/viewtopic.php?f=14&t=17 // include the library code:
#include //Declare Serial Read variables int CmdCount=1; byte inData; char inChar; String BuildINString=""; String DisplayString=""; long DisplayValue; String SentMessage=""; int ByteCount=0; long A; int B; int WorkingVal; String WorkingString=""; //Declare Buttons int MenuID=0; // initialize the library with the numbers of the interface pins LiquidCrystal lcd(8, 9, 4, 5, 6, 7); void setup() { // set up the LCD's number of columns and rows: lcd.begin(16, 2); // Print a message to the LCD. lcd.setCursor(0, 0); Bootup();//Simulate Bootup process doesnt have to be here this only makes it look cool Retry: lcd.setCursor(0, 0); lcd.print("Connecting...... "); lcd.setCursor(0, 1); lcd.print(" "); Serial.begin(38400); delay(500); //Send a test message to see if the ELM327 Chip is responding SentMessage = "ATI"; Serial.println("ATI");delay(500);ReadData(); if (BuildINString.substring(1,7)=="ELM327") { lcd.setCursor(0, 0); lcd.print("Welcome... "); lcd.setCursor(0, 1); lcd.print("Connection OK "); delay(1500); } else { lcd.setCursor(0, 0); lcd.print("Error "); lcd.setCursor(0, 1); lcd.print("No Connection! "); delay(1500); goto Retry; } delay(1500); } void loop() { int x; x = analogRead (0); //Serial.println(x); lcd.setCursor(10,1); if (x > 800 and x < 820){lcd.print ("Select ");} if (x > 620 and x < 630){if (MenuID>0){MenuID--;}delay(250);}//Left if (x > 400 and x < 415){lcd.print ("Down ");} if (x > 190 and x < 215){lcd.print ("Up ");} if (x > -10 and x < 10){if (MenuID<11){MenuID++;}delay(250);} //Right if if if if if if if if if if if if

(MenuID==0){lcd.setCursor(0, 0);lcd.print("01 Coolant Temp (MenuID==1){lcd.setCursor(0, 0);lcd.print("02 IAT Temp (MenuID==2){lcd.setCursor(0, 0);lcd.print("03 Ambient Temp (MenuID==3){lcd.setCursor(0, 0);lcd.print("04 Throttle % (MenuID==4){lcd.setCursor(0, 0);lcd.print("05 CAT 1 Temp (MenuID==5){lcd.setCursor(0, 0);lcd.print("06 CAT 2 Temp (MenuID==6){lcd.setCursor(0, 0);lcd.print("07 CAT 3 Temp (MenuID==7){lcd.setCursor(0, 0);lcd.print("08 CAT 4 Temp (MenuID==8){lcd.setCursor(0, 0);lcd.print("09 RPM (MenuID==9){lcd.setCursor(0, 0);lcd.print("10 Vehicle Speed (MenuID==10){lcd.setCursor(0, 0);lcd.print("11 Air Flow Rate (MenuID==11){lcd.setCursor(0, 0);lcd.print("12 Barometric

");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0, ");lcd.setCursor(0,

1);lcd.print(DisplayString);SentMessage 1);lcd.print(DisplayString);SentMessage 1);lcd.print(DisplayString);SentMessage 1);lcd.print(DisplayString);SentMessage 1);lcd.print("Not Implemented ");} 1);lcd.print("Not Implemented ");} 1);lcd.print("Not Implemented ");} 1);lcd.print("Not Implemented ");} 1);lcd.print(DisplayString);SentMessage 1);lcd.print(DisplayString);SentMessage 1);lcd.print(DisplayString);SentMessage 1);lcd.print(DisplayString);SentMessage

} //Read Data and act accordingly


= = = =

"01 "01 "01 "01

05";Serial.println 0F";Serial.println 46";Serial.println 11";Serial.println

= = = =

"01 "01 "01 "01

0C";Serial.println 0D";Serial.println 10";Serial.println 33";Serial.println

void ReadData() { BuildINString=""; while(Serial.available() > 0) { inData=0; inChar=0; inData = Serial.read(); inChar=char(inData); BuildINString = BuildINString + inChar; } //if(BuildINString!=""){Serial.print(BuildINString);} BuildINString.replace(SentMessage,""); BuildINString.replace(">",""); BuildINString.replace("OK",""); BuildINString.replace("STOPPED",""); BuildINString.replace("SEARCHING",""); BuildINString.replace("NO DATA",""); BuildINString.replace("?",""); BuildINString.replace(",",""); //Serial.print(BuildINString); //Check which OBD Command was sent and calculate VALUE //Calculate RPM I.E Returned bytes wil be 41 0C 1B E0 if (SentMessage=="01 0C") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); WorkingString = BuildINString.substring(11,13); B = strtol(WorkingString.c_str(),NULL,0); DisplayValue = ((A * 256)+B)/4; DisplayString = String(DisplayValue) + " rpm "; lcd.setCursor(0, 1); lcd.print(DisplayString); } //Calculate Vehicle speed I.E Returned bytes wil be 41 0C 1B E0 if (SentMessage=="01 0D") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); DisplayValue = A; DisplayString = String(DisplayValue) + " km/h lcd.setCursor(0, 1); lcd.print(DisplayString); }

";

//Coolant Temp if (SentMessage=="01 05") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); DisplayValue = A; DisplayString = String(DisplayValue) + " C lcd.setCursor(0, 1); lcd.print(DisplayString); }

";

//IAT Temp if (SentMessage=="01 0F") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); DisplayValue = A; DisplayString = String(DisplayValue) + " C lcd.setCursor(0, 1); lcd.print(DisplayString); }

";

//Air flow Rate if (SentMessage=="01 10") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); WorkingString = BuildINString.substring(11,13); B = strtol(WorkingString.c_str(),NULL,0); DisplayValue = ((A * 256)+B)/100; DisplayString = String(DisplayValue) + " g/s lcd.setCursor(0, 1); lcd.print(DisplayString); }

";

//Ambient Temp if (SentMessage=="01 46") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); DisplayValue = A; DisplayString = String(DisplayValue) + " C lcd.setCursor(0, 1); lcd.print(DisplayString); }

";


//Throttle position if (SentMessage=="01 11") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); DisplayValue = A; DisplayString = String(DisplayValue) + " % lcd.setCursor(0, 1); lcd.print(DisplayString); } //Barometric pressure if (SentMessage=="01 33") { WorkingString = BuildINString.substring(7,9); A = strtol(WorkingString.c_str(),NULL,0); DisplayValue = A; DisplayString = String(DisplayValue) + " kpa lcd.setCursor(0, 1); lcd.print(DisplayString); } } void Bootup() { lcd.print("WisperChip V2.00 "); for (int i=0; i <= 5; i++) { for (int j=1; j <= 4; j++)// -/|\{ if(j==1){lcd.setCursor(0, 1);lcd.print if(j==2){lcd.setCursor(0, 1);lcd.print if(j==3){lcd.setCursor(0, 1);lcd.print if(j==4){lcd.setCursor(0, 1);lcd.print } }

";

";

("-");delay(200);} ("/");delay(200);} ("|");delay(200);} ("\\");delay(200);}

delay(1000); }

Step 3: Hooking it up to your vehicle, Once you have programmed the Arduino, make sure the Arduino's TX/RX pins are connected to the TX/RX pins on the ELM327 board. The Code ensures that its able to talk to the ELM327 Chip by sending a command "ATI" the ELM327 chip will respond with ELM327, if it doesn't the LCD will print "Error, No Connection" if it worked it will welcome you wuth a welcome message on the LCD. From there you simply press the left and right buttons to cycle through the menus currently it will only read. Coolant Temp,IAT Temp,Ambient Temp, Throttle %,RPM,Vehicle Speed, Air flow Rate,Barometric Pressure You can add more if you like and change the menu to your liking See Wiki http://en.wikipedia.org/wiki/OBD-II_PIDs for more PID's that you can add there are quite a few. You can use a cellphone cradle that you stuck agains the window to hold it and use a USB cellphone charger to power the Arduino, The ELM327 will be powered by the OBD port on Pin 16 which is positive and PIN4/5 which is negative. If you get stuck feel free to check out on this forum http://techtinker.co.za/viewforum.php?f=14 you may also contact me if you have questions. Please also see the youtube video. Good Luckl!


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Comments 3 comments

Add Comment

atispixs says:

Jan 13, 2015. 2:47 AM REPLY

I already follow your instruction. The ELM327 has return ELM327 by using ATI command. Yet when I send 01 0C or 01 0D to retrieve the RPM and speed, ELM327 is not seem to return the current value. It is always 0 value. I hope you have any suggestion for me. Thank you for sharing your knowledge.

liquidhandwash says: That is cool, great work


Jan 5, 2015. 12:15 AM REPLY

seamster says: Thanks for sharing this!


Oct 10, 2014. 3:18 PM REPLY

Hack an ELM327 Cable to Make an Arduino OBD2 Scann

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