AUTOSAR-COMStack-003_SignalGroup如何发送&接收

1. Ref

Ref.1 AUTOSAR_RS_Main.pdf

Ref.1 AUTOSAR_RS_Features.pdf

Ref.2 AUTOSAR_SRS_COM.pdf

Ref.3 AUTOSAR_SWS_COM.pdf

2. 为什么要使用Signal Group？

2.1 Traceabilty

[RS_PO_00004] AUTOSAR shall define an open architecture for automotive software. (Ref.1)

[RS_Main_00430] AUTOSAR shall support established automotive communication standards (Ref.2)

[RS_BRF_01632] AUTOSAR communication shall support data consistency of groups of signals (Ref.3)

[SRS_Com_02041] The AUTOSAR module shall handle complex data types as a consistent set of data (Ref.4)

[SWS_Com_00050] If Com_SendSignalGroup is called for the signal group, the AUTOSAR COM module shall copy the shadow buffer atomically to the I-PDU buffer.

[SWS_Com_00051] If Com_ReceiveSignalGroup is called for a signal group, the AUTOSAR COM module shall copy the data atomically from the I-PDU buffer to the shadow buffer.

2.2 分析

为什么要使用Signal Group呢？

我们从需求追溯关系入手，按图索骥，搞明白Signal Group相关需求的上游需求来源。

从需求[SRS_Com_02041], [RS_BRF_01632]来看，Signal Group机制主要用于发送，接收复杂数据类型的信号，并保持其一致性。换言之，若一个应用数据比较富足，有多个子数据类型组成，如结构体，若仍旧使用Signal机制，就需要分开进行发送，很难保证一个信号中的子数据类型的一致性。故而绑定各个子数据类型，一起更新，从而保证一致性。

2.3 如何使用 SignalGroup?

假设信号signal_a, signal_b 属于Signal Group group_x， 那么如何发送和接收信号呢？示例如下：

• 如何发送Signal Group

* copy a to shadow buffer */  
Com_SendSignal (signal_a, &a); 
 
 /* copy b to shadow buffer */  
Com_SendSignal (signal_b, &b);  
 
/* copy shadow buffer to I-PDU */  
Com_SendSignalGroup (group_x); 

• 如何接收Signal Group

/* copy I-PDU to shadow buffer */  
Com_ReceiveSignalGroup (group_x);  
 
/* copy a from shadow buffer */  
Com_ReceiveSignal (signal_a, &a);  
 
/* copy b from shadow buffer */  
Com_ReceiveSignal (signal_b, &b);