【AUTOSAR-IpduM】-2.1-创建并配置一个发送TX的(Multiplexed-I-PDU)多路复用

### S32K Microcontroller CAN FD External Loopback Mode Configuration and Usage In automotive applications, the Controller Area Network with Flexible Data-rate (CAN FD) allows higher data rates within a single message compared to traditional CAN. For testing purposes, configuring an external loopback mode on the S32K series microcontrollers can be beneficial as it enables sending messages that are immediately received by another channel of the same controller or even different controllers connected externally. To configure the CAN FD interface into external loopback mode: #### Setting Up Hardware Connections Ensure physical connections between two separate CAN transceivers linked via their differential pairs (CAN_H and CAN_L). One end connects to TX pins while the other connects to RX pins ensuring proper termination resistors are present at each node[^1]. #### Software Initialization Steps The following code snippet demonstrates initializing the CAN module for operation in external loopback using the MCAL layer provided by NXP's AutoSAR implementation specific to S32K devices: ```c #include "Can.h" void Can_InitExternalLoopBack(void){ /* Initialize CAN driver */ CanDrv_Init(); /* Configure CAN FD settings including bitrate switch support */ Can_PduType TxPdu; Can_SetControllerMode(CAN_CHANNEL_0, CAN_MODE_CONFIGURATION); /* Set up filter masks/acceptance codes if necessary */ Can_SetFilterMask(0xFF, 0xFF); // Example mask /* Enable External Loop Back Mode */ Can_EnableExternalLoopBack(CAN_CHANNEL_0); /* Start communication after setting all parameters */ Can_StartCommunication(CAN_CHANNEL_0); } ``` This function initializes the CAN peripheral according to requirements such as enabling flexible data rate features which may involve changing bit timing configurations dynamically during transmission based upon whether standard or extended frames are being used[^2]. For actual message transmission/reception under this setup, one would typically send out PDUs through `Can_Write()` API calls targeting PDU IDs associated with transmit buffers configured earlier; meanwhile receiving them back over receive buffer(s). #### Testing Considerations When performing tests in external loopback scenarios, ensure both ends operate synchronously regarding baudrates especially when transitioning from arbitration phase speeds to payload phases where differing rates might apply depending on network design choices made previously. --related questions-- 1. What tools are recommended for analyzing waveforms generated during CAN FD transmissions? 2. How does altering CAN FD bit timings affect overall system performance? 3. Are there any limitations imposed by hardware or software concerning maximum achievable throughput in external loopback setups? 4. In what situations should internal versus external loopbacks be preferred for diagnostic activities?