// Mode 1 PIDs
#define PID_ENGINE_LOAD 0x04
#define PID_COOLANT_TEMP 0x05
#define PID_SHORT_TERM_FUEL_TRIM_1 0x06
#define PID_LONG_TERM_FUEL_TRIM_1 0x07
#define PID_SHORT_TERM_FUEL_TRIM_2 0x08
#define PID_LONG_TERM_FUEL_TRIM_2 0x09
#define PID_FUEL_PRESSURE 0x0A
#define PID_INTAKE_MAP 0x0B
#define PID_RPM 0x0C
#define PID_SPEED 0x0D
#define PID_TIMING_ADVANCE 0x0E
#define PID_INTAKE_TEMP 0x0F
#define PID_MAF_FLOW 0x10
#define PID_THROTTLE 0x11
#define PID_AUX_INPUT 0x1E
#define PID_RUNTIME 0x1F
#define PID_DISTANCE_WITH_MIL 0x21
#define PID_COMMANDED_EGR 0x2C
#define PID_EGR_ERROR 0x2D
#define PID_COMMANDED_EVAPORATIVE_PURGE 0x2E
#define PID_FUEL_LEVEL 0x2F
#define PID_WARMS_UPS 0x30
#define PID_DISTANCE 0x31
#define PID_EVAP_SYS_VAPOR_PRESSURE 0x32
#define PID_BAROMETRIC 0x33
#define PID_CATALYST_TEMP_B1S1 0x3C
#define PID_CATALYST_TEMP_B2S1 0x3D
#define PID_CATALYST_TEMP_B1S2 0x3E
#define PID_CATALYST_TEMP_B2S2 0x3F
#define PID_CONTROL_MODULE_VOLTAGE 0x42
#define PID_ABSOLUTE_ENGINE_LOAD 0x43
#define PID_AIR_FUEL_EQUIV_RATIO 0x44
#define PID_RELATIVE_THROTTLE_POS 0x45
#define PID_AMBIENT_TEMP 0x46
#define PID_ABSOLUTE_THROTTLE_POS_B 0x47
#define PID_ABSOLUTE_THROTTLE_POS_C 0x48
#define PID_ACC_PEDAL_POS_D 0x49
#define PID_ACC_PEDAL_POS_E 0x4A
#define PID_ACC_PEDAL_POS_F 0x4B
#define PID_COMMANDED_THROTTLE_ACTUATOR 0x4C
#define PID_TIME_WITH_MIL 0x4D
#define PID_TIME_SINCE_CODES_CLEARED 0x4E
#define PID_ETHANOL_FUEL 0x52
#define PID_FUEL_RAIL_PRESSURE 0x59
#define PID_HYBRID_BATTERY_PERCENTAGE 0x5B
#define PID_ENGINE_OIL_TEMP 0x5C
#define PID_FUEL_INJECTION_TIMING 0x5D
#define PID_ENGINE_FUEL_RATE 0x5E
#define PID_ENGINE_TORQUE_DEMANDED 0x61
#define PID_ENGINE_TORQUE_PERCENTAGE 0x62
#define PID_ENGINE_REF_TORQUE 0x63
#define PID_ODOMETER 0xA6

typedef enum {
    PROTO_AUTO = 0x0,
    PROTO_ISO_9141_2 = 0x3,
    PROTO_KWP2000_5KBPS = 0x4,
    PROTO_KWP2000_FAST = 0x5,
    PROTO_ISO15765_11B_500K = 0x6,
    PROTO_ISO15765_29B_500K = 0x7,
    PROTO_ISO15765_29B_250K = 0x8,
    PROTO_ISO15765_11B_250K = 0x9,
    PROTO_J1939 = 0xB,
    PROTO_ISO11898_11B_500K = 0xC,
    PROTO_ISO11898_29B_500K = 0xD,
    PROTO_ISO11898_11B_250K = 0xE,
    PROTO_ISO11898_29B_250K = 0xF    
} OBD_PROTOCOLS;

// states
typedef enum {
    OBD_DISCONNECTED = 0,
    OBD_CONNECTING = 1,
    OBD_CONNECTED = 2,
    OBD_FAILED = 3
} OBD_STATES;