[AUTOSAR com 1. introduction to communication protocol stack]

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1、 First let's look at COM stack Architecture diagram
1 CAN Communication protocol stack concept

AUTOSAR The communication stack is located in the runtime environment （RTE） And microcontroller abstraction layer （MCAL） Between , It can simplify ECU Communication services between , Realize data interaction between different types or rate buses . stay AUTOSAR In the communication stack , The communication module is located in the service layer （Communication,Com）, Diagnose the communication management module （Diagnositic Communication Manager,Dem）、 Protocol data unit routing module （Protocol Data Unit Router,PduR）, Protocol data unit multiplexing module （I-PDU Multiplexer,IpduM）、 Bus related transmission module （ Such as CanTp,FrTp etc. ） And communication and network management related modules ; be located ECU The abstract layer is the interface module related to the bus （ Such as CanIf,LinIf etc. ）; Located in the microcontroller abstraction layer is the bus related driver module （ Such as Can,Lin etc. ）

AUTOSAR The communication stack hides the attributes of bus related protocols and messages from the application layer . In basic CAN For example, communication , The sending mechanism is **RTE–>COM–>PduR–>CanIf–>CAN Driver,** The process is described as follows ：

Com The module obtains the signal of the application layer （Signal）, After certain treatment, it is packaged as I-PDU（Interaction Layer Protocol Data Unit） Send to PduR modular ;
PduR Specified in the module Routing Protocol I-PDU Target receiving module , Will receive I-PDU After certain processing, send it to CanIf;
CanIf Put the signal in L-PDU（Data Link Layer Protocol Data Unit） In the form of CAN Driver module

2 CAN Introduction to communication protocol module
2.1 Com modular
Com The module is located in the runtime environment RTE And PduR Between modules , Its main functions include ：

Load the signal into I-PDU Sent in , Received from I-PDU The signal is parsed from the ;
Provide signal routing function , Will receive I-PDU The signals in are packaged to transmit I-PDU in ;
Communication transmission control （ start-up / stop it I-PDU Group ）
Send a response to a request, etc .
For each Com I-PDU Need to set I-PDU Transmission direction of （ComIPduDirection）、 Signal processing mode （ComIPduSignalProcessing）、 type （ComIPduSignalRef）、 Of I-PDU Working group （ComIPduGroupRef）、Com Signal reference （ComIPduSignalRef）、 overall situation PDU quote （ComPduIdRef） etc. .

2.2 PduR modular
PduR The module is mainly a communication interface module 、 Transport protocol module 、 The diagnosis communication management module and the communication module provide information based on I-PDU Routing services for . It plays a connecting role in the communication protocol stack , It shields the network details for the upper service basic software modules and applications , Make the upper basic software modules and applications do not care about running on that kind of bus network . meanwhile ,PduR The module provides based on I-PDU The gateway function of , It makes communication between different buses possible .

2.3 CanIf modular
CAN The interface layer （CanIf） Is access CAN Standard interface of bus .CanIf Abstract the CAN Location information of the controller , And provide a unified interface to the upper module , Shield the difference of the lower layer , That is, the upper level doesn't care CAN Is the controller an on-chip device of a microcontroller or an off chip device .

CANIf Main functions of the module ： Finish right CanIf And initialization of global variables and configuration buffers in the controller ; Send request service , Provide upper application in CAN Send... Over the network PDU The interface of ; Send confirmation service , Notify the upper layer after sending successfully , Or send the cancellation confirmation and save it in the send cache ; Receive instruction services , Successfully received PDU And then notify the upper layer .

CANIf The module is mainly configured as a hardware object handle （Hardware object handle,Hoh）, Include Hth（Hardware transmit handle） and Hrh（Hardware receive handle）, They need references Can Module CAN Hardware objects .

2.4 ComM modular
Communication management module （Communication Manager,ComM） It can simplify the initialization of bus communication stack 、 Network management, etc , And can collect / Coordinate bus communication access requests . It mainly provides three communication modes ：

COMM_FULL_COMMUNICATION:FULL Communication mode , This status can be received and sent
COMM_SILENT_COMMUNICATION:SILENT Communication mode , This status can only be received
COMM_NO_COMMUNICATION:NO Communication mode , Communication is not possible in this state

2.5 CanSM modular
CAN State Manager （CAN State Manager,CanSM） Responsible for implementation CAN Abstraction of network control process , It's for ComM Module supply API To request CAN The network switches the communication mode .

3 MCal And Can modular [2]
CAN drive （CAN Driver） It belongs to the communication driver in the microcontroller abstraction layer , It is aimed at the internal of microcontroller CAN controller , Can realize the right CAN Initialization of the controller 、 send out / receive CAN message 、 Indication of receiving message and confirmation of sending message 、 Wake up detection 、 Functions such as overflow and error handling .CAN Drivers can access hardware , And provide independent hardware to the upper layer API.