ArduinoHondaUNI

An arduino code that reads Honda OBD Protocol via the 3 pin DLC connector.

Please refer to the screenshots below.

Applications

• Datalogging
• Diagnostics
• Trip Computer
• Custom Cluster
• Etc

Supports

• Honda ECU's before 2002

Files

• ArduinoHondaUNI - top level code.
• app - implements Honda OBD protocol
• eeprom - implements storage
• display - implements display
• elm - implements the translation to elm protocol (serial)
• button - implements single button

Wiring for ECU connection

Honda 3 Pin DLC           Arduino Nano
Gnd --------------------- Gnd
+12 --------------------- Vin
K-line ------------------ Pin12

Wiring for button

Tact Switch               Arduino Nano
(+) --------------------- Pin17 (A3)
(-) --------------------- Gnd

Wiring for buzzer (beep)

Piezo Buzzer              Arduino Nano
(+) --------------------- Pin13
(-) --------------------- Gnd

Wiring for ELM (Bluetooth hc-05/hc-06)

HC-05 Bluetooth           Arduino Nano
Rx ---------------------- Pin11
Tx ---------------------- Pin10

Wiring for display option 1 (lcd1602 i2c)

LCD 16x2                  Arduino Nano
Sda --------------------- Pin18 (A4)
Scl --------------------- Pin19 (A5)
Vcc --------------------- 5v
Gnd --------------------- Gnd

Wiring for display option 2 (lcd128x64 spi)

LCD 128x64                Arduino Nano
D4 ---------------------- Pin7
D5 ---------------------- Pin6
D6 ---------------------- Pin5

Wiring for display option 3 (lcd1602 Parallel)

LCD 16x2                  Arduino Uno               
RS ---------------------- Pin9
Enable ------------------ Pin8
D4 ---------------------- Pin7
D5 ---------------------- Pin6
D6 ---------------------- Pin5
D7 ---------------------- Pin4
VO ---------------------- 10k Potentiometer (+5V to Gnd)

Wiring for voltage sensor

Voltage Divider           Arduino Nano
+12V divider circuit ---- Pin14 (A0)
(680k ohms and 220k ohms)

User Manual

• Button
  • Short press to change page
  • Hold 3 seconds to change mode (obd1/obd2)
  • Hold 5 seconds to reset the ecu
• Display
• ELM Bluethoth
  • using an app (Torque or similar) connect via bluetooth (mode obd2)
  • direct honda PID access
    • 1 byte access pid "21AA" where: 2 = custom header, 1 = 1 byte, AA = address
    • 2 bytes access pid "22AA" where: 2 = custom header, 2 = 2 bytes, AA = address
    • 4 byte access pid "24AA" where: 2 = custom header, 4 = 4 bytes, AA = address
• Unit Measurement
  • rpm
  • kph
  • km
  • kpa
  • millivolt
  • degree

Note

• Tested on P2T ODB2 stock and P30 ODB1 chipped