标准CAN(ISO 15765-4)OBD要求所有消息都有8个数据字节 - (ELM327文档)
使用蓝牙ELM327从我的车上读取我得到的信息并非全是8字节长。
这是配置:
AT Z # Reset
AT D # Default
AT SP 6 # Set Protocol
AT CFC1 # Flowcontrol
AT D1 # Show DLC
AT AL # Allow long messages
AT H1 # Show headers
AT CAF0 # Disable Formatting
AT L0 # Disable linefeeds
AT S0 # Remove whitespace
输出 :
Command: AT MA
17A8FFFFFFAA00F031A3
17E8FFFFFF00FF4000FF
186719503203200020
0C6880637FFF800E8E82
2BC8948641FD03891D73
18A6FFF000064000
1F68DE20003700FFFFFF
1F88F504826FFE000A0D
391600008000C000
12E8C77FFF7FE0FFFF00
24270200FFEFFE000C
29C800000000FFFF0000
35245C000000
130800286FFE009FFECD
17A8FFFFFFAA00F031A3
17E8F
BUFFER FULL
这里大多数消息是正确的(3字节ID + 1字节DLC + 8字节数据),但有些更短,有时我收到更长的消息。这些正常吗?如果没有,任何想法可能来自哪里?
确实,所有OBD相关(即标准化)消息都有8个字节的数据。但是,您发布的跟踪不包含任何OBD消息。
OBD消息的CAN-ID介于0x7DF和0x7EF之间
输出中的消息似乎是其他(制造商特定的)CAN消息。制造商可以自由定义这些消息的格式,因此允许小于8的DLC。
这个听OBDII的样本可以协议:
idv: 0 exID: 80012CC ID: 580 DLC: 08 DATA: 00 00 00 00 00 00 00 00
idv: 0 exID: 80012CC ID: 316 DLC: 08 DATA: 01 1E AC 09 1E 1C 00 5E
idv: 0 exID: 80012CC ID: 0A1 DLC: 08 DATA: 78 7F 00 00 1D 00 00 00
idv: 0 exID: 80012CC ID: 580 DLC: 08 DATA: 00 00 00 00 00 00 00 00
idv: 0 exID: 80012CC ID: 545 DLC: 08 DATA: 80 00 00 8A 00 00 00 00
idv: 0 exID: 80012CC ID: 316 DLC: 08 DATA: 01 1E AC 09 1E 1C 00 5E
idv: 0 exID: 80012CC ID: 580 DLC: 08 DATA: 00 00 00 00 00 00 00 00
idv: 0 exID: 80012CC ID: 545 DLC: 08 DATA: 80 47 00 8B 00 00 00 00
idv: 0 exID: 80012CC ID: 580 DLC: 08 DATA: 00 00 00 00 00 00 00 00
idv: 0 exID: 80012CC ID: 7DF DLC: 08 DATA: 02 01 0C 00 00 00 00 00
idv: 0 exID: 80012CC ID: 7E8 DLC: 08 DATA: 04 41 0C 09 9C 00 00 00
idv: 0 exID: 80012CC ID: 580 DLC: 08 DATA: 00 00 00 00 00 00 00 00
idv: 0 exID: 80012CC ID: 545 DLC: 08 DATA: 80 00 00 8A 00 00 00 00
idv: 0 exID: 80012CC ID: 316 DLC: 08 DATA: 01 1E 98 09 1E 1C 00 5E
idv: 0 exID: 80012CC ID: 580 DLC: 08 DATA: 00 00 00 00 00 00 00 00
idv: 0 exID: 80012CC ID: 545 DLC: 08 DATA: 80 00 00 8B 00 00 00 00
idv: 0 exID: 80012CC ID: 545 DLC: 08 DATA: 80 00 00 8B 00 00 00 00
idv: 0 exID: 80012CC ID: 580 DLC: 08 DATA: 00 00 00 00 00 00 00 00
每个传感器模块和...使用可以相互传输数据
但这里是用于读取RPM的ELM327发送和接收数据包
idv: 0 exID: 80012CC ID: 7DF DLC: 08 DATA: 02 01 0C 00 00 00 00 00
idv: 0 exID: 80012CC ID: 7E8 DLC: 08 DATA: 04 41 0C 09 9C 00 00 00
如你所见,DLC的数据包总是8个字节,can协议的第一个数据位就是该数据包中的数据字节数
DATA:02 01 0C 00 00 00 00 00数据字节数= 02数据= 01 0C(RPM读取命令)