1、简介
诊断服务是介于诊断设备和ECU之间的一种信息交互方式。通常由诊断设备发出请求，ECU做出回应。
doCAN：基于CAN协议的诊断
DoIP：Diagnostic communication Over IP (DoIP) is a standard developed by ISO-13400 for vehicle communication over the Internet Protocol (IP).
2、官方标准
doCAN
ISO 14229-1:2020 Road vehicles - Unified diagnostic services (UDS) – Part1: Application layer
ISO 14229-2-2013 Road vehicles - Unified diagnostic services (UDS) – Part 2:Session layer services
ISO 14229-3-2012, Road vehicles - Unified diagnostic services (UDS) - Part 3: Unified
diagnostic services on CAN implementation (UDSonCAN)
ISO 15765-1-2011, Road vehicles - Diagnostic communication over Controller Area
Network (DoCAN) - Part 1: General information and use case definition
ISO 15765-2-2016, Road vehicles - Diagnostic communication over Controller Area
Network (DoCAN) - Part 2: Transport protocol and network layer services
ISO 15765-4-2016, Road vehicles - Diagnostic communication over Controller Area
Network (DoCAN) - Part 4: Requirements for emissions-related systems
Vehicle Unified diagnostic services (UDS) Standard
doip
| Reference id | Title | Version/Date |
| [ISO13400-1] | ISO 13400-1:Communication between test equipment and vehicles over Internet Protocol –Part 1: General information and use case definition | SO 13400-1:2011 |
| [ISO13400-2] | ISO 13400-2:Communication between test equipment and vehicles over Internet Protocol –Part 2: Network and Transport Layer Requirements and Services | ISO 13400-2:2012 |
3、时间参数设置
应用层时间参数
| Parameter | Symbol | Nominal | Unit |
| Time between client (tester) request and server (ECU) response | P2 server | 50 | ms |
| P2 client | n/a | ms | |
| Enhanced timeout for the client to wait after the reception of a negative response message with response code 78 hex | P2* server | tbd | ms |
| P2* client | n/a | ms | |
| Time between request and the next request from the tester –physical | P3 client_phys | n/a | ms |
| Time between consecutive request from the tester – functional | P3 client_func | n/a | ms |
P2 server
ECU 收到Tester发送的request 起到ECU 响应的时间。
P2 Client
诊断仪在成功发出请求之后，会期望在一定的时间内收到响应，这个时间就是P2Client
P2* service
ECU 发送NRC 0X78开始计时到发送下一响应需要的时间
P2* Client
P2*Client与P2Client类似，当诊断仪在没有超时的情况下收到NRC 0X78后，就会启动这个时间参数
P3Client_Phys和P3Client_Func：
这两个参数定义诊断仪在发送完一条UDS命令之后，下次再发送命令的最小时间间隔，分别适用于物理寻址和功能寻址的情况。在ISO24229中，它俩的值与P2Client相同
会话层时间参数
| Parameter | Symbol | Nominal | Timeout | Unit |
| Session timeout; after timeout return to default-session | S3 server | n/a | 5000 | ms |
| Time for transmitting next TesterPresent to keep non- default session | S3 client | 2000 | ＜S3 server | ms |
S3Server：
在讲UDS服务的时候，说过ECU需要收到诊断服务才能维持在某个非default session中，或者收到诊断仪持续发送的3E服务，testerpresent。S3Server定义的是ECU多长时间收不到任何诊断服务会回退到default session中。该参数在实际项目中，工厂会通过OBD口或者OTA过程发送 3E 服务 维持ECU服务。
S3Client：
S3Client与S3Server相对应，它定义的是诊断仪发送3E服务（testerpresent）的循环周期。一般设置为2s。
具体项目上述参数会有一点差异，不过
