1、转自 http:/ J1939 学习笔记 (一)1.总线布局2.差分信号线J1939 通讯传输的是一系列的“1”或“0” 。 1 代表在 J1939（+）与 J1939（-）之间是高电压差。0 代表在 J1939（+）与 J1939（-）之间是低电压差250K 波特率时，在 J1939 高、低导线间的电压从 0 到 1 每秒变化 250K 次是可能的。用一个高频示波器可以看到此电压变化。3.ISO 标准对应Layer1 J1939/11: 物理层，物理介质 ,总线的设计, 长度,节点, 等等.Layer2 J1939/21: 数据层，定义分类 PGN 信息/传输协议.Layer3 J1939/
2、31: 网络层，定义不同网络互连之间的转换技术。Layer7 J1939/71: 应用层，信息分享、解析。J1939/73: 应用层，故障信息。4.术语SPN特定参数特定参数对应的号码，例如：SPN 190 = 发动机转速SPN 513 = % 扭矩PGN 参数 组号码 总线上的信息被以 “组”的形式广播，例如：PGN 61444 =发动机控制器 #1 (EEC1)PGN 61444 = SPN 190, SPN 513,等等.发动机转速和扭矩百分比都属于 PGN 61444 参数组。优先级告诉 ECM 接收的信息的重要性:0 = 最重要6 = 最不重要例如：如果变速箱用优先级请求发动机升速，
3、而牵引控制器用优先级请求发动机降速，最终发动机会选择降速。源地址和目的地址指示信息是从哪一个控制器发出，或发送到哪一个控制器。00h发动机控制器主机01h发动机控制器辅机03h变速箱5.CAN 标准帧和扩展帧标准帧只有 11 位的标识符（ID）扩展帧有 11+18=29 位标识符（ID）以后均以扩展帧作介绍。6.协议数据单元（PDU ）标识符+数据域= 协议数据单元（PDU ）。7.参数组编号（PGN）PGN（Parameter Group Number）参数组编号：参数组编号唯一标识一个参数组，在通讯过程中起到“索引” 的作用，表征报文的内容和用途，确定报文的类型和传播数据需要的帧数目。可以
4、理解为同类（或者有共同特征的设备）参数的集合的索引。SAEJ1939 中的格式规定如下：pgn61443 Electronic EngineController #2 EEC2 Transmission Repetition Rate: 50ms -信息发送周期Data Length: 8 Bytes -数据域长度（ CAN 扩展帧中的数据域）Data Page: 0 -数据页（PGN 中的数据页 DP）PDU Format: 240 -PDU 格式（PDU1（PDU 特定域（PF优先级 Parameter Group Number: 61443 (00F00316) -PGNBit Star
5、t Position / Byte Length SPNDescription SPN （对应的SPN 号） -数据域分布1.1 2 bits Accelerator Pedal Low Idle Switch 558 -1.1 表示第一个字节第一位1.3 2 bits Accelerator Pedal Kickdown Switch 559 -2bits 表示该 SPN 对应的数据长度1.5 2 bits Road Speed Limit 14372 1 byte Accelerator Pedal Position 913 1 byte Percent Load at Current S
6、peed 924 1 byte Remote Accelerator 9748.特定参数号（SPN ）spn91 Accelerator PedalPosition The ratio of actual acceleratorpedal position to maximum pedal position. Although it is used as an input to determine transmission and ASRalgorithms about drivers actions.Data Length: 1 Bytes -SPN 号对应的数据的长度Resolution:
7、 0.4%/ bit, 0 offset -计算方式（见下）Data Range: 0 to100% -数据范围（涉及偏移量计算）Type: MeasuredSuspect Parameter Number: 91 -SPN 号Parameter Group Number: 61443 -隶属的 PGN 号由 SPN 数据（CAN 格式中的读出的数据）计算实际的数据方法：如下是一个实际的 J1939 信息0.1000 1 OCF00300x Rx d8 7DC3 C0 2D FFFFFFFF转换步骤：十六进制转成十进制乘以转换系数加上偏置举例：查询 PGN：SPN110 如下：SPN175：S
8、AE J1939 学习笔记 (二)特殊的 J1939 信息（车辆控制）pgn0 - TSC1pgn65226 -DM1pgn60160 10 ms to engine, 50ms toretarderData Length: 8 bytesData Page: 0PDU Format: 0PDU Specific: DADefault Priority: 3Parameter Group Number: 0 ( 00000016 )Bit Start Position /Bytes Length SPNDescription SPN1.1 2 bits OverrideControl Mode
9、 6951.3 2 bits RequestedSpeed Control Conditions 6961.5 2 bits OverrideControl Mode Priority 8972-3 2 bytes RequestedSpeed/Speed Limit 8984 1 byte RequestedTorque/Torque Limit 518数据域举例如下：相应 SPN 介绍SPN695 - Override Control Mode00 Override disable01 Speed Control Governs to a desiredSpeed10 Torque Con
10、trol Maintains a desired Torque value11 Speed/Torque Limit Control Controls to the lowest value.SPN897 -Override Control Mode Priority00 Highest Priority01 High Priority10 Medium Priority11 Low PrioritySPN696 - Requested Speed Control ConditionsBasedon these bits (bits 4,3 in byte 1) up to Four (4)
11、different ASGgainsets can be applied DYNAMICALLY.00 =Gainset 1 01 =Gainset2 10 =Gainset 311 =Gainset 4This can be a significant advantage when the TSC1 is being used in speed control toaccomplish the applications intended function. Ex: Improve load pickup during loadedoperations and then switch to d
12、ifferentgainsetfor stability during light loading.spn898- Requested Speed/Speed Limit -This is the engine speed which the engine is expected to operate at ifthe speed control mode is active or the engine speed which the engine is not expected to exceed if the speed limit mode is active.Data Length:
13、2bytesResolution: 0.125 rpm/bit , 0 offsetData Range: 0 to 8,031.875 rpmType: StatusSuspect Parameter Number: 898Parameter Group Number: 0 -PGN No from previous slideAsthis is an SPN, dont forget to Byte Swap when converting hence 0100 0000 0011 1000 swapped is 0011 100001000000To convert informatio
14、n-CovertBinary to Decimal-Multiplyby Resolution-AddOffsetHence: 00111000 0100 0000 = 38 40hConvert to Dec: 3840h = 14400 DecMultiply by 0.125: 14400x 0.125 = 1800Add 0: 1800 + 0 =1800Result: 1800 rpmspn518-Requested Torque/Torque Limit - This is the engine torque at which the engine is expected to o
15、perate ifthe torque control mode is active or the engine torque which the engine is notexpected to exceed if the torque limit mode is active.Data Length: 1 byteResolution: 1 %/bit , -125 % offsetData Range: -125 to 125 %Operating Range: 0 to 125% engine torquerequestsType: StatusSuspect Parameter Number: 518Parameter Group Number: 0 -PGN No from previous slideHence: 10010110 = 96hConvert to Dec: 96h = 150 DecMultiply by 1: 150x 1 = 150Add -125: 150 -125 = 25Result: 25% TQSAE J1939 学习笔记 (三)J1939 故障代码种类J1939 由几个不同的诊断信息：诊断信息 1 - DM1 现行故障代码
