This is a simple yet powerful library to effortlessly interface your Arduino with an ELM327 OBD-II scanner. With this library, you can query any and all OBD-II supported PIDs to collect a wide variety of car data (i.e. speed, rpm, engine temp, etc). Also, you can use ELMduino to view and clear your car's trouble codes - no need ot go to AutoZone anymore!
Install ELMduino using the Arduino IDE's Libraries Manager (search "ELMduino.h")
If you're having difficulty in connecting/keeping connection to your ELM327, try using 38400 baud instead of 115200.
#include <SoftwareSerial.h>
#include "ELMduino.h"
SoftwareSerial mySerial(2, 3); // RX, TX
#define ELM_PORT mySerial
ELM327 myELM327;
uint32_t rpm = 0;
void setup()
{
pinMode(LED_BUILTIN, OUTPUT);
digitalWrite(LED_BUILTIN, HIGH);
Serial.begin(115200);
ELM_PORT.begin(115200);
Serial.println("Attempting to connect to ELM327...");
if (!myELM327.begin(ELM_PORT))
{
Serial.println("Couldn't connect to OBD scanner");
while (1);
}
Serial.println("Connected to ELM327");
}
void loop()
{
float tempRPM = myELM327.rpm();
if (myELM327.status == ELM_SUCCESS)
{
rpm = (uint32_t)tempRPM;
Serial.print("RPM: "); Serial.println(rpm);
}
else
{
Serial.print(F("\tERROR: "));
Serial.println(myELM327.status);
delay(100);
}
}const char AUTOMATIC = '0';
const char SAE_J1850_PWM_41_KBAUD = '1';
const char SAE_J1850_PWM_10_KBAUD = '2';
const char ISO_9141_5_BAUD_INIT = '3';
const char ISO_14230_5_BAUD_INIT = '4';
const char ISO_14230_FAST_INIT = '5';
const char ISO_15765_11_BIT_500_KBAUD = '6';
const char ISO_15765_29_BIT_500_KBAUD = '7';
const char ISO_15765_11_BIT_250_KBAUD = '8';
const char ISO_15765_29_BIT_250_KBAUD = '9';
const char SAE_J1939_29_BIT_250_KBAUD = 'A';
const char USER_1_CAN = 'B';
const char USER_2_CAN = 'C';const uint8_t SUPPORTED_PIDS_1_20 = 0; // 0x00 - bit encoded
const uint8_t MONITOR_STATUS_SINCE_DTC_CLEARED = 1; // 0x01 - bit encoded
const uint8_t FREEZE_DTC = 2; // 0x02 -
const uint8_t FUEL_SYSTEM_STATUS = 3; // 0x03 - bit encoded
const uint8_t ENGINE_LOAD = 4; // 0x04 - %
const uint8_t ENGINE_COOLANT_TEMP = 5; // 0x05 - °C
const uint8_t SHORT_TERM_FUEL_TRIM_BANK_1 = 6; // 0x06 - %
const uint8_t LONG_TERM_FUEL_TRIM_BANK_1 = 7; // 0x07 - %
const uint8_t SHORT_TERM_FUEL_TRIM_BANK_2 = 8; // 0x08 - %
const uint8_t LONG_TERM_FUEL_TRIM_BANK_2 = 9; // 0x09 - %
const uint8_t FUEL_PRESSURE = 10; // 0x0A - kPa
const uint8_t INTAKE_MANIFOLD_ABS_PRESSURE = 11; // 0x0B - kPa
const uint8_t ENGINE_RPM = 12; // 0x0C - rpm
const uint8_t VEHICLE_SPEED = 13; // 0x0D - km/h
const uint8_t TIMING_ADVANCE = 14; // 0x0E - ° before TDC
const uint8_t INTAKE_AIR_TEMP = 15; // 0x0F - °C
const uint8_t MAF_FLOW_RATE = 16; // 0x10 - g/s
const uint8_t THROTTLE_POSITION = 17; // 0x11 - %
const uint8_t COMMANDED_SECONDARY_AIR_STATUS = 18; // 0x12 - bit encoded
const uint8_t OXYGEN_SENSORS_PRESENT_2_BANKS = 19; // 0x13 - bit encoded
const uint8_t OXYGEN_SENSOR_1_A = 20; // 0x14 - V %
const uint8_t OXYGEN_SENSOR_2_A = 21; // 0x15 - V %
const uint8_t OXYGEN_SENSOR_3_A = 22; // 0x16 - V %
const uint8_t OXYGEN_SENSOR_4_A = 23; // 0x17 - V %
const uint8_t OXYGEN_SENSOR_5_A = 24; // 0x18 - V %
const uint8_t OXYGEN_SENSOR_6_A = 25; // 0x19 - V %
const uint8_t OXYGEN_SENSOR_7_A = 26; // 0x1A - V %
const uint8_t OXYGEN_SENSOR_8_A = 27; // 0x1B - V %
const uint8_t OBD_STANDARDS = 28; // 0x1C - bit encoded
const uint8_t OXYGEN_SENSORS_PRESENT_4_BANKS = 29; // 0x1D - bit encoded
const uint8_t AUX_INPUT_STATUS = 30; // 0x1E - bit encoded
const uint8_t RUN_TIME_SINCE_ENGINE_START = 31; // 0x1F - sec
const uint8_t SUPPORTED_PIDS_21_40 = 32; // 0x20 - bit encoded
const uint8_t DISTANCE_TRAVELED_WITH_MIL_ON = 33; // 0x21 - km
const uint8_t FUEL_RAIL_PRESSURE = 34; // 0x22 - kPa
const uint8_t FUEL_RAIL_GUAGE_PRESSURE = 35; // 0x23 - kPa
const uint8_t OXYGEN_SENSOR_1_B = 36; // 0x24 - ratio V
const uint8_t OXYGEN_SENSOR_2_B = 37; // 0x25 - ratio V
const uint8_t OXYGEN_SENSOR_3_B = 38; // 0x26 - ratio V
const uint8_t OXYGEN_SENSOR_4_B = 39; // 0x27 - ratio V
const uint8_t OXYGEN_SENSOR_5_B = 40; // 0x28 - ratio V
const uint8_t OXYGEN_SENSOR_6_B = 41; // 0x29 - ratio V
const uint8_t OXYGEN_SENSOR_7_B = 42; // 0x2A - ratio V
const uint8_t OXYGEN_SENSOR_8_B = 43; // 0x2B - ratio V
const uint8_t COMMANDED_EGR = 44; // 0x2C - %
const uint8_t EGR_ERROR = 45; // 0x2D - %
const uint8_t COMMANDED_EVAPORATIVE_PURGE = 46; // 0x2E - %
const uint8_t FUEL_TANK_LEVEL_INPUT = 47; // 0x2F - %
const uint8_t WARM_UPS_SINCE_CODES_CLEARED = 48; // 0x30 - count
const uint8_t DIST_TRAV_SINCE_CODES_CLEARED = 49; // 0x31 - km
const uint8_t EVAP_SYSTEM_VAPOR_PRESSURE = 50; // 0x32 - Pa
const uint8_t ABS_BAROMETRIC_PRESSURE = 51; // 0x33 - kPa
const uint8_t OXYGEN_SENSOR_1_C = 52; // 0x34 - ratio mA
const uint8_t OXYGEN_SENSOR_2_C = 53; // 0x35 - ratio mA
const uint8_t OXYGEN_SENSOR_3_C = 54; // 0x36 - ratio mA
const uint8_t OXYGEN_SENSOR_4_C = 55; // 0x37 - ratio mA
const uint8_t OXYGEN_SENSOR_5_C = 56; // 0x38 - ratio mA
const uint8_t OXYGEN_SENSOR_6_C = 57; // 0x39 - ratio mA
const uint8_t OXYGEN_SENSOR_7_C = 58; // 0x3A - ratio mA
const uint8_t OXYGEN_SENSOR_8_C = 59; // 0x3B - ratio mA
const uint8_t CATALYST_TEMP_BANK_1_SENSOR_1 = 60; // 0x3C - °C
const uint8_t CATALYST_TEMP_BANK_2_SENSOR_1 = 61; // 0x3D - °C
const uint8_t CATALYST_TEMP_BANK_1_SENSOR_2 = 62; // 0x3E - °C
const uint8_t CATALYST_TEMP_BANK_2_SENSOR_2 = 63; // 0x3F - °C
const uint8_t SUPPORTED_PIDS_41_60 = 64; // 0x40 - bit encoded
const uint8_t MONITOR_STATUS_THIS_DRIVE_CYCLE = 65; // 0x41 - bit encoded
const uint8_t CONTROL_MODULE_VOLTAGE = 66; // 0x42 - V
const uint8_t ABS_LOAD_VALUE = 67; // 0x43 - %
const uint8_t FUEL_AIR_COMMANDED_EQUIV_RATIO = 68; // 0x44 - ratio
const uint8_t RELATIVE_THROTTLE_POSITION = 69; // 0x45 - %
const uint8_t AMBIENT_AIR_TEMP = 70; // 0x46 - °C
const uint8_t ABS_THROTTLE_POSITION_B = 71; // 0x47 - %
const uint8_t ABS_THROTTLE_POSITION_C = 72; // 0x48 - %
const uint8_t ACCELERATOR_PEDAL_POSITION_D = 73; // 0x49 - %
const uint8_t ACCELERATOR_PEDAL_POSITION_E = 74; // 0x4A - %
const uint8_t ACCELERATOR_PEDAL_POSITION_F = 75; // 0x4B - %
const uint8_t COMMANDED_THROTTLE_ACTUATOR = 76; // 0x4C - %
const uint8_t TIME_RUN_WITH_MIL_ON = 77; // 0x4D - min
const uint8_t TIME_SINCE_CODES_CLEARED = 78; // 0x4E - min
const uint8_t MAX_VALUES_EQUIV_V_I_PRESSURE = 79; // 0x4F - ratio V mA kPa
const uint8_t MAX_MAF_RATE = 80; // 0x50 - g/s
const uint8_t FUEL_TYPE = 81; // 0x51 - ref table
const uint8_t ETHONOL_FUEL_PERCENT = 82; // 0x52 - %
const uint8_t ABS_EVAP_SYS_VAPOR_PRESSURE = 83; // 0x53 - kPa
const uint8_t EVAP_SYS_VAPOR_PRESSURE = 84; // 0x54 - Pa
const uint8_t SHORT_TERM_SEC_OXY_SENS_TRIM_1_3 = 85; // 0x55 - %
const uint8_t LONG_TERM_SEC_OXY_SENS_TRIM_1_3 = 86; // 0x56 - %
const uint8_t SHORT_TERM_SEC_OXY_SENS_TRIM_2_4 = 87; // 0x57 - %
const uint8_t LONG_TERM_SEC_OXY_SENS_TRIM_2_4 = 88; // 0x58 - %
const uint8_t FUEL_RAIL_ABS_PRESSURE = 89; // 0x59 - kPa
const uint8_t RELATIVE_ACCELERATOR_PEDAL_POS = 90; // 0x5A - %
const uint8_t HYBRID_BATTERY_REMAINING_LIFE = 91; // 0x5B - %
const uint8_t ENGINE_OIL_TEMP = 92; // 0x5C - °C
const uint8_t FUEL_INJECTION_TIMING = 93; // 0x5D - °
const uint8_t ENGINE_FUEL_RATE = 94; // 0x5E - L/h
const uint8_t EMISSION_REQUIREMENTS = 95; // 0x5F - bit encoded
const uint8_t SUPPORTED_PIDS_61_80 = 96; // 0x60 - bit encoded
const uint8_t DEMANDED_ENGINE_PERCENT_TORQUE = 97; // 0x61 - %
const uint8_t ACTUAL_ENGINE_TORQUE = 98; // 0x62 - %
const uint8_t ENGINE_REFERENCE_TORQUE = 99; // 0x63 - Nm
const uint8_t ENGINE_PERCENT_TORQUE_DATA = 100; // 0x64 - %
const uint8_t AUX_INPUT_OUTPUT_SUPPORTED = 101; // 0x65 - bit encoded(https://www.sparkfun.com/datasheets/Widgets/ELM327_AT_Commands.pdf)
const char * const DISP_DEVICE_DESCRIPT = "AT @1"; // General
const char * const DISP_DEVICE_ID = "AT @2"; // General
const char * const STORE_DEVICE_ID = "AT @3 %s"; // General
const char * const REPEAT_LAST_COMMAND = "AT \r"; // General
const char * const ALLOW_LONG_MESSAGES = "AT AL"; // General
const char * const AUTOMATIC_RECEIVE = "AT AR"; // OBD
const char * const ADAPTIVE_TIMING_OFF = "AT AT0"; // OBD
const char * const ADAPTIVE_TIMING_AUTO_1 = "AT AT1"; // OBD
const char * const ADAPTIVE_TIMING_AUTO_2 = "AT AT2"; // OBD
const char * const DUMP_BUFFER = "AT BD"; // OBD
const char * const BYPASS_INIT_SEQUENCE = "AT BI"; // OBD
const char * const TRY_BAUD_DIVISOR = "AT BRD %s"; // General
const char * const SET_HANDSHAKE_TIMEOUT = "AT BRT %s"; // General
const char * const CAN_AUTO_FORMAT_OFF = "AT CAF0"; // CAN
const char * const CAN_AUTO_FORMAT_ON = "AT CAF1"; // CAN
const char * const CAN_EXTENDED_ADDRESS_OFF = "AT CEA"; // CAN
const char * const USE_CAN_EXTENDED_ADDRESS = "AT CEA %s"; // CAN
const char * const SET_ID_FILTER = "AT CF %s"; // CAN
const char * const CAN_FLOW_CONTROL_OFF = "AT CFC0"; // CAN
const char * const CAN_FLOW_CONTROL_ON = "AT CFC1"; // CAN
const char * const SET_ID_MASK = "AT CM %s"; // CAN
const char * const SET_CAN_PRIORITY = "AT CP %s"; // CAN
const char * const SHOW_CAN_STATUS = "AT CS"; // CAN
const char * const CAN_SILENT_MODE_OFF = "AT CSM0"; // CAN
const char * const CAN_SILENT_MODE_ON = "AT CSM1"; // CAN
const char * const CALIBRATE_VOLTAGE_CUSTOM = "AT CV %s"; // Volts
const char * const RESTORE_CV_TO_FACTORY = "AT CV 0000"; // Volts
const char * const SET_ALL_TO_DEFAULTS = "AT D"; // General
const char * const DISP_DLC_OFF = "AT D0"; // CAN
const char * const DISP_DLC_ON = "AT D1"; // CAN
const char * const MONITOR_FOR_DM1_MESSAGES = "AT DM1"; // J1939
const char * const DISP_CURRENT_PROTOCOL = "AT DP"; // OBD
const char * const DISP_CURRENT_PROTOCOL_NUM = "AT DPN"; // OBD
const char * const ECHO_OFF = "AT E0"; // General
const char * const ECHO_ON = "AT E1"; // General
const char * const FLOW_CONTROL_SET_DATA_TO = "AT FC SD %s"; // CAN
const char * const FLOW_CONTROL_SET_HEAD_TO = "AT FC SH %s"; // CAN
const char * const FLOW_CONTROL_SET_MODE_TO = "AT FC SM %s"; // CAN
const char * const FORGE_EVENTS = "AT FE"; // General
const char * const PERFORM_FAST_INIT = "AT FI"; // ISO
const char * const HEADERS_OFF = "AT H0"; // OBD
const char * const HEADERS_ON = "AT H1"; // OBD
const char * const DISP_ID = "AT I"; // General
const char * const SET_ISO_BAUD_10400 = "AT IB 10"; // ISO
const char * const SET_ISO_BAUD_4800 = "AT IB 48"; // ISO
const char * const SET_ISO_BAUD_9600 = "AT IB 96"; // ISO
const char * const IFR_VAL_FROM_HEADER = "AT IFR H"; // J1850
const char * const IFR_VAL_FROM_SOURCE = "AT IFR S"; // J1850
const char * const IFRS_OFF = "AT IFR0"; // J1850
const char * const IFRS_AUTO = "AT IFR1"; // J1850
const char * const IFRS_ON = "AT IFR2"; // J1850
const char * const IREAD_IGNMON_INPUT_LEVEL = "AT IGN"; // Other
const char * const SET_ISO_SLOW_INIT_ADDRESS = "AT IIA %s"; // ISO
const char * const USE_J1939_ELM_DATA_FORMAT = "AT JE"; // J1850
const char * const J1939_HEAD_FORMAT_OFF = "AT JHF0"; // J1850
const char * const J1939_HEAD_FORMAT_ON = "AT JHF1"; // J1850
const char * const USE_J1939_SAE_DATA_FORMAT = "AT JS"; // J1850
const char * const SET_J1939_TIMER_X_TO_1X = "AT JTM1"; // J1850
const char * const SET_J1939_TIMER_X_TO_5X = "AT JTM5"; // J1850
const char * const DISP_KEY_WORDS = "AT KW"; // ISO
const char * const KEY_WORD_CHECKING_OFF = "AT KW0"; // ISO
const char * const KEY_WORD_CHECKING_ON = "AT KW1"; // ISO
const char * const LINEFEEDS_OFF = "AT L0"; // General
const char * const LINEFEEDS_ON = "AT L1"; // General
const char * const LOW_POWER_MODE = "AT LP"; // General
const char * const MEMORY_OFF = "AT M0"; // General
const char * const MEMORY_ON = "AT M1"; // General
const char * const MONITOR_ALL = "AT MA"; // OBD
const char * const MONITOR_FOR_PGN = "AT MP %s"; // J1939
const char * const MONITOR_FOR_RECEIVER = "AT MR %s"; // OBD
const char * const MONITOR_FOR_TRANSMITTER = "AT MT %s"; // OBD
const char * const NORMAL_LENGTH_MESSAGES = "AT NL"; // OBD
const char * const SET_PROTO_OPTIONS_AND_BAUD = "AT PB %s"; // OBD
const char * const PROTOCOL_CLOSE = "AT PC"; // OBD
const char * const ALL_PROG_PARAMS_OFF = "AT PP FF OFF"; // PPs
const char * const ALL_PROG_PARAMS_ON = "AT PP FF ON"; // PPs
const char * const SET_PROG_PARAM_OFF = "AT PP %s OFF"; // PPs
const char * const SET_PROG_PARAM_ON = "AT PP %s ON"; // PPs
const char * const SET_PROG_PARAM_VAL = "AT PP %s SV %s"; // PPs
const char * const DISP_PP_SUMMARY = "AT PPS"; // PPs
const char * const RESPONSES_OFF = "AT R0"; // OBD
const char * const RESPONSES_ON = "AT R1"; // OBD
const char * const SET_RECEIVE_ADDRESS_TO = "AT RA %s"; // OBD
const char * const READ_STORED_DATA = "AT RD"; // General
const char * const SEND_RTR_MESSAGE = "AT RTR"; // CAN
const char * const READ_VOLTAGE = "AT RV"; // Volts
const char * const PRINTING_SPACES_OFF = "AT S0"; // OBD
const char * const PRINTING_SPACES_ON = "AT S1"; // OBD
const char * const STORE_DATA_BYTE = "AT SD "; // General
const char * const SET_HEADER = "AT SH "; // OBD
const char * const PERFORM_SLOW_INIT = "AT SI"; // ISO
const char * const SET_PROTOCOL_TO_AUTO_H_SAVE = "AT SP A%c"; // OBD
const char * const SET_PROTOCOL_TO_H_SAVE = "AT SP %c"; // OBD
const char * const SET_PROTOCOL_TO_AUTO_SAVE = "AT SP 00"; // OBD
const char * const SET_REC_ADDRESS = "AT SR %s"; // OBD
const char * const SET_STANDARD_SEARCH_ORDER = "AT SS"; // OBD
const char * const SET_TIMEOUT_TO_H_X_4MS = "AT ST %s"; // OBD
const char * const SET_WAKEUP_TO_H_X_20MS = "AT SW %s"; // ISO
const char * const SET_TESTER_ADDRESS_TO = "AT TA %s"; // OBD
const char * const TRY_PROT_H_AUTO_SEARCH = "AT TP A%s"; // OBD
const char * const TRY_PROT_H = "AT TP %s"; // OBD
const char * const VARIABLE_DLC_OFF = "AT V0"; // CAN
const char * const VARIABLE_DLC_ON = "AT V1"; // CAN
const char * const SET_WAKEUP_MESSAGE = "AT WM"; // ISO
const char * const WARM_START = "AT WS"; // General
const char * const RESET_ALL = "AT Z"; // General