Read iso15031 protocol data stream

Request support from the vehicle PID term
All emission related OBD ECU, If at least ISO 15031 A service defined in , Support services 0x01 and PID=0x00.
service 0x01 and PID：0x00 Defined as all emissions related OBD ECUs Common to “initialization/keep alive/ping” news .
1、 The equipment shall be installed in accordance with 11 position CAN-ID(0x7DF) To request , See if the vehicle supports , If you support it , What data streams are available .
OBD The external test equipment initializes and determines the baud rate After setting the baud rate ,
The request is as follows ：7DF 02 01 00 00 00 00 00 00
ECU#1 Respond to ：7E8 06 41 00 98 3B A0 17 00
In this response ,
06： Response valid data length 6 Bytes ;
41： service 01 The corresponding response SID;
00： Respond to PID, In response to the request PID;
98( Binary system 10011000)： On behalf of 0x01~0x08 Between PID Medium 0x01、0x04、0x05;
3B( Binary system 00111011)： On behalf of 0x09~0x10 Between PID Medium 0x0B、0x0C、0x0D、0x0F、0x10;
A0( Binary system 10100000)： On behalf of 0x11~0x18 Between PID Medium 0x11、0x13;
17( Binary system 00010111)： On behalf of 0x19~0x20 Between PID Medium 0x1C、0x1E、0x1F、0x20;
Be careful ： Support 0x20 Of PID, Explain that there is support in the follow-up PID. Need to continue sending service 0x01 and PID=0x20 Request .
The request is as follows ：7DF 02 01 20 00 00 00 00 00
ECU#1 Respond to ：7E8 06 41 20 A0 13 A0 01 00
In this response ,
06： Response valid data length 6 Bytes ;
41： service 01 The corresponding response SID;
20： Respond to PID, In response to the request PID;
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01( Binary system 00000001)： On behalf of 0x39~0x40 Between PID Medium 0x40;
Be careful ： Support 0x40 Of PID, Explain that there is support in the follow-up PID. Need to continue sending service 0x01 and PID：0x40 Request .
Follow this rule , Until there is no support PID. such as ： service 0x01 and PID=0x80 Request
The request is as follows ：7DF 02 01 80 00 00 00 00 00
ECU#1 Respond to ：7E8 06 41 80 EE 00 00 00 00
The vehicle does not support 0xA0 Of PID, There is no need to send the service again 0x01 and PID=0xA0 The request of .

	** Be careful ： Some cars have multiple ECU Respond to **, such as ：
	 The request is as follows ：7DF		02 01 00 00 00 00 00 00
	ECU#1 Respond to ：7E8 		06 41 00 98 3B A0 17 00
	ECU#2 Respond to ：7E9 		06 41 00 80 08 00 00 00
	 explain 
	ECU#1 (ECM) Support the following PID: 0x01、0x04、0x05、0x0B~0x0D、0x0F~0x11、0x13、0x1C、0x1E~0x20.
	ECU#2 (TCM) Support the following PID: 0x01 and 0x0D.

2、 According to the first 1 Support requested PID, Request specific data streams in turn .
Such as engine speed , lookup SAE J1979-DA, Its PID by 0x0C, The vehicle supports this PID,
The request is as follows ：7DF 02 01 0C 00 00 00 00 00
#ECU1 Respond to ：7E8 04 41 0C 0A EE 00 00 00
Analyze according to the agreement ：

0xAEE=2798;2798*0.25=699.5（rpm）.

When the effective data length is greater than 7 Byte time , Multi frame transmission is required . for instance ,NOx sensor PID by 0x83, The response valid data is 11 byte .
The request is as follows ： 7DF 02 01 83 00 00 00 00 00
Respond to ： 7E8 10 0B 41 83 03 00 EA 00
according to ISO 15765-2 agreement , First frame data received , The valid data length is 0x00B(12 position )=11 byte , You need to send a stream control frame to request subsequent data .

Flow control frame ：7DF 30 00 01 00 00 00 00 00
Respond to ： 7E8 21 C8 FF FF FF FF 00 00

The valid data of the response is ：41 83 03 00 EA 00 C8 FF FF FF FF, according to SAE J1979-DA in PID=0x83 analysis ：
41： service 01 The corresponding response SID;
83： Respond to PID, In response to the request PID;
03( Binary system 00000011)： Support NOx Sensor concentration library 1 sensor 1, Support NOx Sensor concentration library 1 sensor 2;
00EA：NOx Sensor concentration library 1 sensor 1 The value is 234(ppm);
00C8：NOx Sensor concentration library 1 sensor 2 The value is 200(ppm);

3、 If 11 position CAN-ID No answer , Description not supported 11 position CAN-ID(0x7DF). use 29 position CAN-ID(0x18DB33F1) To request ：
request ：18DB33F1 02 01 00 00 00 00 00 00
Respond to ：18DAF100 06 41 00 98 3B A0 17 00
The specific data analysis is the same as 11 position CAN-ID.