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Arduino-based-diag OBD-II_programação.pdf

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Arduino-based OBD-II Interface and Data Logger CS 497 Independent Study Ryan Miller Advisor: Prof. Douglas Comer April 26, 2011
Arduino • Italy 2005 • ATmega328 microcontroller • 14 digital I/O pins • 16 MHz clock speed • 32 KB memory • About $30 online Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions
Arduino • Program “sketches” in Multi-platform Java- based IDE • Code in C/C++ • Serial Communication (currently USB)
Hardware • Goals of this project: • Communicate with an automotive engine control unit (ECU) via the Arduino • Gather and record instantaneous data that is reported by the vehicle Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions ?
Hardware • Vehicles produced in the U.S. after 1996 are required to have an OBD-II (on-board diagnostic) connector
Hardware • OBD-II Interface • Very simple connection for most applications • Most important pins • K-Line • Ground • +12V
Hardware • Open-source project called “OBDuino” offered the interface schematic (which is fortunate, because I am not an EE major)
Hardware • Open-source project called “OBDuino” offered the interface schematic (which is fortunate, because I am not an EE major)
Hardware • Freescale MC33290 handles the tricky parts • K-Line, Ground, and +12V go in • Serial Tx/Rx come out
Hardware OBD-II
Software • A few functions to perform: • Initialize ISO connection • Request data from vehicle’s ECU • Display the result on the LCD and record the value to retrieve later Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions
Software • Initialization: • Starts by “bit-banging” 0x33 at 5 baud • i.e. 0 0 1 1 0 0 1 1 200ms pause = 1.6 seconds
Software • Initialization: • Starts by “bit-banging” 0x33 at 5 baud • Code: byte  b  =  0x33;     for  (byte  mask  =  0x01;  mask;  mask  <<=  1)   {    if  (b  &  mask)  //  Choose  bit      digitalWrite(K_OUT,  HIGH);  //  Send  1    else      digitalWrite(K_OUT,  LOW);  //  Send  0        delay(200);   }  
Software • Then you can start 10.4 kbps communication and perform these steps to finish initialization:
Software • Parameter IDs (PIDs) • SAE J1979 standard • Examples: PID Bytes Description Formula 0x0C 2 Engine RPM ((A*256)+B)/4 0x0D 1 Vehicle Speed (km/h) A 0x11 1 Throttle Position (%) A*100/255 0x3F 2 Catalyst Temp (B2, S2) ((A*256)+B)/10 - 40
Software • Steps: 1. Request PID with hex value 2. Continuously read data from ISO until successful checksum or timeout 3. Convert returned value with formula 4. Display / record value and repeat
Software 1. Request PID with hex value Index Value Description 0 0x68 SAE J1979 standard 1 0x6A OBD-II request 2 0xF1 Off-board tool 3 0x01 Mode 1 PIDs 4 pid Hex value for PID requested 5 Checksum Computed from message byte  message[6];   for  (int  i  =  0;  i  <  6;  i++)    iso_write_byte(message[i]);  
Software 2. Continuously read data from ISO until successful checksum or timeout Byte(s) Description 0 Message Header 1 1 Message Header 2 2 Source Address 3 – 9 Data (up to 7 bytes) Final byte Checksum byte  buf[11];  
Software 3. Convert returned value with formula ie.: PID Bytes Description Formula 0x0C 2 Engine RPM ((A*256)+B)/4 double  rpm;     rpm  =  ((double)buf[0]  *  256)  +  (double)buf[1])  /  4.0;  
Software 4. Record/display value and repeat • Displaying on an LCD screen: LiquidCrystal  lcd;     lcd.print(rpm);    
Software 4. Record/display value and repeat • Writing to an SD card: File  log;     log.print(rpm);    
Software • One last note on PIDs… • This gives you the rate of air in grams / second PID Bytes Description Formula 0x10 2 Mass Air Flow Rate ((A*256)+B)/100
Software • You can convert into • And then use vehicle speed to convert to or MPG g air s gal gasoline h miles gal gasoline
Data • Scanned four PIDs over a 20-minute interval every 1-2 seconds • Vehicle Speed • Engine RPM • Engine Coolant • Calculated MPG Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions
Data mph
Data mph rpm
Data °C
Data mph °C
Conclusions • Embedded computing is ubiquitous • Massive amounts of data generated by everyday machines • Elec. Engineering and CS can come together to make some pretty cool things Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions
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Arduino-based-diag OBD-II_programação.pdf

  • 1. Arduino-based OBD-II Interface and Data Logger CS 497 Independent Study Ryan Miller Advisor: Prof. Douglas Comer April 26, 2011
  • 2. Arduino • Italy 2005 • ATmega328 microcontroller • 14 digital I/O pins • 16 MHz clock speed • 32 KB memory • About $30 online Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions
  • 3. Arduino • Program “sketches” in Multi-platform Java- based IDE • Code in C/C++ • Serial Communication (currently USB)
  • 4. Hardware • Goals of this project: • Communicate with an automotive engine control unit (ECU) via the Arduino • Gather and record instantaneous data that is reported by the vehicle Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions ?
  • 5. Hardware • Vehicles produced in the U.S. after 1996 are required to have an OBD-II (on-board diagnostic) connector
  • 6. Hardware • OBD-II Interface • Very simple connection for most applications • Most important pins • K-Line • Ground • +12V
  • 7. Hardware • Open-source project called “OBDuino” offered the interface schematic (which is fortunate, because I am not an EE major)
  • 8. Hardware • Open-source project called “OBDuino” offered the interface schematic (which is fortunate, because I am not an EE major)
  • 9. Hardware • Freescale MC33290 handles the tricky parts • K-Line, Ground, and +12V go in • Serial Tx/Rx come out
  • 11. Software • A few functions to perform: • Initialize ISO connection • Request data from vehicle’s ECU • Display the result on the LCD and record the value to retrieve later Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions
  • 12. Software • Initialization: • Starts by “bit-banging” 0x33 at 5 baud • i.e. 0 0 1 1 0 0 1 1 200ms pause = 1.6 seconds
  • 13. Software • Initialization: • Starts by “bit-banging” 0x33 at 5 baud • Code: byte  b  =  0x33;     for  (byte  mask  =  0x01;  mask;  mask  <<=  1)   {    if  (b  &  mask)  //  Choose  bit      digitalWrite(K_OUT,  HIGH);  //  Send  1    else      digitalWrite(K_OUT,  LOW);  //  Send  0        delay(200);   }  
  • 14. Software • Then you can start 10.4 kbps communication and perform these steps to finish initialization:
  • 15. Software • Parameter IDs (PIDs) • SAE J1979 standard • Examples: PID Bytes Description Formula 0x0C 2 Engine RPM ((A*256)+B)/4 0x0D 1 Vehicle Speed (km/h) A 0x11 1 Throttle Position (%) A*100/255 0x3F 2 Catalyst Temp (B2, S2) ((A*256)+B)/10 - 40
  • 16. Software • Steps: 1. Request PID with hex value 2. Continuously read data from ISO until successful checksum or timeout 3. Convert returned value with formula 4. Display / record value and repeat
  • 17. Software 1. Request PID with hex value Index Value Description 0 0x68 SAE J1979 standard 1 0x6A OBD-II request 2 0xF1 Off-board tool 3 0x01 Mode 1 PIDs 4 pid Hex value for PID requested 5 Checksum Computed from message byte  message[6];   for  (int  i  =  0;  i  <  6;  i++)    iso_write_byte(message[i]);  
  • 18. Software 2. Continuously read data from ISO until successful checksum or timeout Byte(s) Description 0 Message Header 1 1 Message Header 2 2 Source Address 3 – 9 Data (up to 7 bytes) Final byte Checksum byte  buf[11];  
  • 19. Software 3. Convert returned value with formula ie.: PID Bytes Description Formula 0x0C 2 Engine RPM ((A*256)+B)/4 double  rpm;     rpm  =  ((double)buf[0]  *  256)  +  (double)buf[1])  /  4.0;  
  • 20. Software 4. Record/display value and repeat • Displaying on an LCD screen: LiquidCrystal  lcd;     lcd.print(rpm);    
  • 21. Software 4. Record/display value and repeat • Writing to an SD card: File  log;     log.print(rpm);    
  • 22. Software • One last note on PIDs… • This gives you the rate of air in grams / second PID Bytes Description Formula 0x10 2 Mass Air Flow Rate ((A*256)+B)/100
  • 23. Software • You can convert into • And then use vehicle speed to convert to or MPG g air s gal gasoline h miles gal gasoline
  • 24. Data • Scanned four PIDs over a 20-minute interval every 1-2 seconds • Vehicle Speed • Engine RPM • Engine Coolant • Calculated MPG Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions
  • 29. Conclusions • Embedded computing is ubiquitous • Massive amounts of data generated by everyday machines • Elec. Engineering and CS can come together to make some pretty cool things Arduino Hardware Automotive OBD ISO Interface Software Data Conclusions