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docs: update Canbus_Support2
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dazq
Josh Stewart
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title: CanBus Support2
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description:
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published: true
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date: 2020-12-15T22:05:17.427Z
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date: 2020-12-15T23:11:49.733Z
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tags:
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editor: markdown
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dateCreated: 2020-12-15T21:58:51.731Z
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@ -56,11 +56,163 @@ The OBD2 port Inteface offers support for ,
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2. Output the Analog/Digital data values from the 16 Aux inputs ([see here for info on aux data input configuration](/en/configuration/Auxillary_IO_Configuration))
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3. Activate External Outputs(coming soon!)
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### Modes Supported
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There are 10 diagnostic services described in the latest OBD-II standard SAE J1979. Before 2002, J1979 referred to these services as "modes". Speeduino supports only a selected number of these modes. These are:
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Mode (hex) Description
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- 01 Show current data
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- 09 Vehicle information (VIN) (coming soon)
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- 22 Manufacturer Specific data.
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Mode 22 is a custom PID mode that is defined by the manufacturer.It is used to define additional services.
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### PID supported
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The following PIDs are supports by by the OBD port
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When using Bit-Encoded-Notation, quantities like C4 means bit 4 from data byte C. Each bit is numerated from 0 to 7, so 7 is the most significant bit and 0 is the least significant bit (See below).
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A B C D
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A7 A6 A5 A4 A3 A2 A1 A0 B7 B6 B5 B4 B3 B2 B1 B0 C7 C6 C5 C4 C3 C2 C1 C0 D7 D6 D5 D4 D3 D2 D1 D0
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#### MODE 01
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PID(hex) PID(Dec) Data bytes returned Description Min value Max value Units Formula[a]
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00 0 4 PIDs supported [01 - 20] Bit encoded [A7..D0] == [PID $01..PID $20] See below
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05 5 1 Engine coolant temperature
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0B 11 1 Intake manifold absolute pressure
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0C 12 2 Engine speed 0 16,383.75 rpm 256 A + B 4 {\displaystyle {\frac {256A+B}{4}}} {\displaystyle {\frac {256A+B}{4}}}
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0D 13 1 Vehicle speed 0 255 km/h A {\displaystyle A} A
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0E 14 1 Timing advance -64 63.5 ° before TDC A 2 − 64 {\displaystyle {\frac {A}{2}}-64} {\displaystyle {\frac {A}{2}}-64}
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0F 15 1 Intake air temperature -40 215 °C A − 40 {\displaystyle A-40} {\displaystyle A-40}
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11 17 1 Throttle position 0 100 % 100 255 A {\displaystyle {\tfrac {100}{255}}A} {\displaystyle {\tfrac {100}{255}}A}
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19 25 2 Oxygen Sensor 6 A: Voltage
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B: Short term fuel trim 0 -100
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1C 28 1 OBD standards this vehicle conforms to 1 250 - enumerated. See below
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20 32 4 PIDs supported [21 - 40] Bit encoded [A7..D0] == [PID $21..PID $40] See below
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22 34 2 Fuel Rail Pressure (relative to manifold vacuum) 0 5177.265 kPa 0.079 ( 256 A + B ) {\displaystyle 0.079(256A+B)} {\displaystyle 0.079(256A+B)}
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24 36 4 Oxygen Sensor 1
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AB: Air-Fuel Equivalence Ratio (lambda,λ)
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CD: Voltage
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25 37 4 Oxygen Sensor 2
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AB: Air-Fuel Equivalence Ratio (lambda,λ)
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CD: Voltage
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33 51 1 Absolute Barometric Pressure 0 255 kPa A {\displaystyle A} A
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40 64 4 PIDs supported [41 - 60] Bit encoded [A7..D0] == [PID $41..PID $60] See below
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42 66 2 Control module voltage 0 65.535 V 256 A + B 1000 {\displaystyle {\frac {256A+B}{1000}}} {\displaystyle {\frac {256A+B}{1000}}}
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46 70 1 Ambient air temperature -40 215 °C A − 40 {\displaystyle A-40} {\displaystyle A-40}
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52 82 1 Ethanol fuel % 0 100 % 100 255 A {\displaystyle {\tfrac {100}{255}}A} {\displaystyle {\tfrac {100}{255}}A}
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5C 92 1 Engine oil temperature -40 210 °C A − 40 {\displaystyle A-40} {\displaystyle A-40}
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60 96 4 PIDs supported [61 - 80] Bit encoded [A7..D0] == [PID $61..PID $80] See below
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#### Bitwise encoded PIDs
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Some of the PIDs in the above table cannot be explained with a simple formula. A more elaborate explanation of these data is provided here:
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Example MODE 01 PID 00
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A request for this PID returns 4 bytes of data (Big-endian). Each bit, from MSB to LSB, represents one of the next 32 PIDs and specifies whether that PID is supported.
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For example, if the car response is BE1FA813, it can be decoded like this:
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Hexadecimal B | E | 1 | F | A | 8 | 1 | 3
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Binary 1 0 1 1 | 1 1 1 0 | 0 0 0 1 | 1 1 1 1 | 1 0 1 0 | 1 0 0 0 | 0 0 0 1 | 0 0 1 1
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Supported? Yes No Yes Yes | Yes Yes Yes No | No No No Yes | Yes Yes Yes Yes |Yes No Yes No | Yes No No No | No No No Yes| No No Yes Yes
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PID number 01 02 03 04 | 05 06 07 08 | 09 0A 0B 0C| 0D 0E 0F 10 | 11 12 13 14 | 15 16 17 18 | 19 1A 1B 1C | 1D 1E 1F 20
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So, supported PIDs are: 01, 03, 04, 05, 06, 07, 0C, 0D, 0E, 0F, 10, 11, 13, 15, 1C, 1F and 20
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#### MODE 22
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Speeduino responds to the Mode 22 request for the following PID:
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PID(hex) PID(Dec) Data bytes returned Description Min value Max value Units Formula[a]
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7701 0 2 AuxIn1 Data
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7702 0 2 AuxIn2 Data
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7703 0 2 AuxIn3 Data
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7704 0 2 AuxIn4 Data
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7705 0 2 AuxIn5 Data
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7706 0 2 AuxIn6 Data
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7707 0 2 AuxIn7 Data
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7708 0 2 AuxIn8 Data
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7709 0 2 AuxIn9 Data
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770A 0 2 AuxIn10 Data
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770B 0 2 AuxIn11 Data
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770C 0 2 AuxIn12 Data
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770D 0 2 AuxIn13 Data
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770E 0 2 AuxIn14 Data
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770F 0 2 AuxIn15 Data
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7710 0 2 AuxIn16 Data
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#### CAN (11-bit) bus format
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The PID query and response occurs on the vehicle's CAN bus. Standard OBD requests and responses use functional addresses. The diagnostic reader initiates a query using CAN ID 7DFh[clarification needed], which acts as a broadcast address, and accepts responses from any ID in the range 7E8h to 7EFh. ECUs that can respond to OBD queries listen both to the functional broadcast ID of 7DFh and one assigned ID in the range 7E0h to 7E7h. Their response has an ID of their assigned ID plus 8 e.g. 7E8h through 7EFh.
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This approach allows up to eight ECUs, each independently responding to OBD queries. The diagnostic reader can use the ID in the ECU response frame to continue communication with a specific ECU. In particular, multi-frame communication requires a response to the specific ECU ID rather than to ID 7DFh.
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CAN bus may also be used for communication beyond the standard OBD messages. Physical addressing uses particular CAN IDs for specific modules (e.g., 720h for the instrument cluster in Fords) with proprietary frame payloads.
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Query
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The functional PID query is sent to the vehicle on the CAN bus at ID 7DFh, using 8 data bytes. The bytes are:
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Byte
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PID Type 0 1 2 3 4 5 6 7
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SAE Standard Number of
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additional
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data bytes:
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2 Service
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01 = show current data;
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02 = freeze frame;
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etc. PID code
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(e.g.: 05 = Engine coolant temperature) not used
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(ISO 15765-2 suggests CCh)
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Vehicle specific Number of
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additional
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data bytes:
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3 Custom service: (e.g.: 22 = enhanced data) PID code
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(e.g.: 4980h) not used
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(ISO 15765-2 suggests CCh)
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Response
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The vehicle responds to the PID query on the CAN bus with message IDs that depend on which module responded. Typically the engine or main ECU responds at ID 7E8h. Other modules, like the hybrid controller or battery controller in a Prius, respond at 07E9h, 07EAh, 07EBh, etc. These are 8h higher than the physical address the module responds to. Even though the number of bytes in the returned value is variable, the message uses 8 data bytes regardless (CAN bus protocol form Frameformat with 8 data bytes). The bytes are:
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Byte
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PID Type 0 1 2 3 4 5 6 7
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SAE Standard
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7E8h,
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7E9h,
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7EAh,
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etc. Number of
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additional
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data bytes:
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3 to 6 Custom service
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Same as query, except that 40h is added to the service value. So:
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41h = show current data;
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42h = freeze frame;
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etc. PID code
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(e.g.: 05 = Engine coolant temperature) value of the specified parameter, byte 0 value, byte 1 (optional) value, byte 2 (optional) value, byte 3 (optional) not used
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(may be 00h or 55h)
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Vehicle specific
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7E8h, or 8h + physical ID of module. Number of
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additional
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data bytes:
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4to 7 Custom service: same as query, except that 40h is added to the service value.(e.g.: 62h = response to service 22h request) PID code
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(e.g.: 4980h) value of the specified parameter, byte 0 value, byte 1 (optional) value, byte 2 (optional) value, byte 3 (optional)
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Vehicle specific
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7E8h, or 8h + physical ID of module. Number of
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additional
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data bytes:
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3 7Fh this a general response usually indicating the module doesn't recognize the request. Custom service: (e.g.: 22h = enhanced diagnostic data by PID, 21h = enhanced data by offset) 31h not used
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(may be 00h)
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