How do we decide on the optimal buffer size in PDUR Configuration

The PduR (PDU Router) buffer size is decided based on multiple factors related to system constraints, communication needs, and the AUTOSAR configuration. Here are the key considerations:

1. Communication Type and Data Flow

• Direct Transmission (Without Buffering): If the PDU is directly routed without needing storage, a buffer is not required.

• Buffered Transmission: If routing requires temporary storage (e.g., when using a gateway or deferred transmission), buffer size must be allocated accordingly.

2. Maximum PDU Size

• The buffer must accommodate the largest PDU that needs to be stored.

• Typically, the size is equal to or slightly larger than the largest PDU size routed through PduR.

3. Number of Pending PDUs

• If multiple PDUs need to be temporarily stored, the buffer size must be large enough to handle peak loads.

• The buffer size = Max PDU size × Number of simultaneous PDUs.

Example: If the max PDU size routed over PduR is 64 bytes and you need to store 2 PDUs at a time, set the buffer size to 128 bytes.

4. Communication Mode (Synchronous vs Asynchronous)

• In synchronous mode, PDUs are processed immediately, reducing buffer requirements.

• In asynchronous mode, buffering is required, leading to larger memory needs.

5. Routing Path and Module Dependencies

• Buffers may be required if there are delays due to routing between different communication stacks (e.g., CAN → LIN).

• The PduR must ensure compatibility with Com, DCM, SoAd, CanTp, LinTp, etc.

6. Memory Constraints

• RAM availability is a key limiting factor.

• If memory is scarce, optimization techniques (e.g., dynamic buffer allocation) may be considered.

7. AUTOSAR Configuration (PduR Configuration Tool)

• The buffer size is typically configured using AUTOSAR configuration tools.

• PduR handles Tx and Rx buffers separately, and parameters are set in the PduR_BufferConfiguration structure.

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