// ============================================================================
// 函数名称: CANMessageReceive()
// 函数功能: CAN接收函数
// 输    入: ui32Base is the base address of the CAN controller
//!       ui32ObjID is the object number to configure (1-32).
//!       pMsgObject is a pointer to a structure containing message object settings.
//!       eMsgType indicates the type of message for this object.
// 输    出: 无
// 扇    入: BspCan_CanRx             // CAN初始化
// 扇    出: 无
// 其它说明: 无
// ===========================================================================
int16 CANMessageReceive(Uint32 ui32Base, Uint32 ui32ObjID, tCANMsgObject *pMsgObject, bool bClrPendingInt)
{
    Uint32 ui32CmdMaskReg = 0;
    Uint32 ui32MaskReg = 0;
    Uint32 ui32ArbReg = 0;
    Uint32 ui32MsgCtrl = 0;
    Uint16 S_Temp = 0;
    int16 Rtv = SYS_CAN_OP_OK;

    ui32CmdMaskReg = (CAN_IF2CMD_DATA_A | CAN_IF2CMD_DATA_B | CAN_IF2CMD_CONTROL | CAN_IF2CMD_MASK | CAN_IF2CMD_ARB);   // This is always a read to the Message object as this call is setting a message object.

    if(bClrPendingInt)                                                                                                  // Clear a pending interrupt and new data in a message object.
    {
        ui32CmdMaskReg |= CAN_IF2CMD_CLRINTPND | CAN_IF2CMD_TXRQST;
    }
    else
    {
        ;
    }

    CAN_ADDR16(ui32Base + CAN_O_IF2CMD + 2) =  ui32CmdMaskReg >> 16;                                                    // Set up the request for data from the message object.
    CAN_ADDR16(ui32Base + CAN_O_IF2CMD) = ui32ObjID & CAN_IF2CMD_MSG_NUM_M;                                             // Transfer the message object to the message object specified by ui32ObjID.

    while(((CAN_ADDR16(ui32Base + CAN_O_IF2CMD) & \
            CAN_IF2CMD_BUSY) != 0) && (S_Temp < 1000))                                                                        // 检查是否处于空闲状态,如果这里通不过，那下面的寄存器都无法操作，因为寄存器都受busy保护
    {
        DELAY_US(1);                                                                                                    // 最多等待1ms后退出
        S_Temp++;                                                                                                       // 通过做实验，这里在初始化的时候不会进入
    }

    if (S_Temp >= 1000)
    {
        S_Temp = 0;                                                                                                     // 退出后将等待计数清理处理
        Rtv = SYS_CAN_OP_ERROR;                                                                                           // 返回CAN接收错误
    }
    else
    {
        S_Temp = 0;
    }

    ui32MaskReg = CAN_ADDR32(ui32Base + CAN_O_IF2MSK);                                                                  // Read out the IF Registers.
    ui32ArbReg  = CAN_ADDR32(ui32Base + CAN_O_IF2ARB);
    ui32MsgCtrl = CAN_ADDR32(ui32Base + CAN_O_IF2MCTL);
    pMsgObject->ui32Flags = MSG_OBJ_NO_FLAGS;

    if((((!(ui32MsgCtrl & CAN_IF2MCTL_TXRQST)) != 0) && ((ui32ArbReg & CAN_IF2ARB_DIR) != 0)) \
            || (((ui32MsgCtrl & CAN_IF2MCTL_TXRQST) != 0) && ((!(ui32ArbReg & CAN_IF2ARB_DIR)) != 0)))  // Determine if this is a remote frame by checking the TXRQST and DIR bits.
    {
        pMsgObject->ui32Flags |= MSG_OBJ_REMOTE_FRAME;
    }
    else
    {
        ;
    }

    if((ui32ArbReg & CAN_IF2ARB_XTD) == CAN_IF2ARB_XTD)                                     // Get the identifier out of the register, the format depends on size of the mask.
    {
        pMsgObject->ui32MsgID = ui32ArbReg & CAN_IF2ARB_ID_M;                               // Set the 29 bit version of the Identifier for this message object.
        pMsgObject->ui32Flags |= MSG_OBJ_EXTENDED_ID;
    }
    else
    {
        pMsgObject->ui32MsgID = (ui32ArbReg & CAN_IF2ARB_STD_ID_M) >> CAN_IF2ARB_STD_ID_S;  // The Identifier is an 11 bit value.
    }

    if((ui32MsgCtrl & CAN_IF2MCTL_MSGLST) == CAN_IF2MCTL_MSGLST)                            // Indicate that we lost some data.
    {
        pMsgObject->ui32Flags |= MSG_OBJ_DATA_LOST;
    }
    else
    {
        ;
    }

    if((ui32MsgCtrl & CAN_IF2MCTL_UMASK) == CAN_IF2MCTL_UMASK)                              // Set the flag to indicate if ID masking was used.
    {
        if((ui32ArbReg & CAN_IF2ARB_XTD) == CAN_IF2ARB_XTD)
        {
            pMsgObject->ui32MsgIDMask = (ui32MaskReg & CAN_IF2MSK_MSK_M);                                           // The Identifier Mask is assumed to also be a 29 bit value.

            if((pMsgObject->ui32MsgIDMask != 0x1fffffff) || ((pMsgObject->ui32Flags & MSG_OBJ_REMOTE_FRAME) == 0))  // If this is a fully specified Mask and a remote frame then don't set the MSG_OBJ_USE_ID_FILTER because the ID was not really filtered.
            {
                pMsgObject->ui32Flags |= MSG_OBJ_USE_ID_FILTER;
            }
            else
            {
                ;
            }
        }
        else
        {
            pMsgObject->ui32MsgIDMask = ((ui32MaskReg & CAN_IF2MSK_MSK_M) >> 18);                                   // The Identifier Mask is assumed to also be an 11 bit value.

            if((pMsgObject->ui32MsgIDMask != 0x7ff) || ((pMsgObject->ui32Flags & MSG_OBJ_REMOTE_FRAME) == 0))       // If this is a fully specified Mask and a remote frame then don't set the MSG_OBJ_USE_ID_FILTER because the ID was not really filtered.
            {
                pMsgObject->ui32Flags |= MSG_OBJ_USE_ID_FILTER;
            }
            else
            {
                ;
            }
        }

        if((ui32MaskReg & CAN_IF2MSK_MXTD) == CAN_IF2MSK_MXTD)                                                      // Indicate if the extended bit was used in filtering.
        {
            pMsgObject->ui32Flags |= MSG_OBJ_USE_EXT_FILTER;
        }
        else
        {
            ;
        }

        if((ui32MaskReg & CAN_IF2MSK_MDIR) == CAN_IF2MSK_MDIR)                                                      // Indicate if direction filtering was enabled.
        {
            pMsgObject->ui32Flags |= MSG_OBJ_USE_DIR_FILTER;
        }
        else
        {
            ;
        }
    }
    else
    {
        ;
    }

    if ((ui32MsgCtrl & CAN_IF2MCTL_TXIE) == CAN_IF2MCTL_TXIE)                                                       // Set the interrupt flags.
    {
        pMsgObject->ui32Flags |= MSG_OBJ_TX_INT_ENABLE;
    }
    else
    {
        ;
    }

    if ((ui32MsgCtrl & CAN_IF2MCTL_RXIE) == CAN_IF2MCTL_RXIE)
    {
        pMsgObject->ui32Flags |= MSG_OBJ_RX_INT_ENABLE;
    }
    else
    {
        ;
    }

    if ((ui32MsgCtrl & CAN_IF2MCTL_NEWDAT) == CAN_IF2MCTL_NEWDAT)                                                     // See if there is new data available.
    {
        pMsgObject->ui32MsgLen = (ui32MsgCtrl & CAN_IF2MCTL_DLC_M);                                                  // Get the amount of data needed to be read.

        if ((pMsgObject->ui32Flags & MSG_OBJ_REMOTE_FRAME) == 0)                                                      // Don't read any data for a remote frame, there is nothing valid in that buffer anyway.
        {
            CANDataRegRead(pMsgObject->pucMsgData, (Uint32 *)(ui32Base + CAN_O_IF2DATA), pMsgObject->ui32MsgLen);  // Read out the data from the CAN registers.
        }
        else
        {
            ;
        }

        CAN_ADDR16(ui32Base + CAN_O_IF2CMD + 2) = CAN_IF2CMD_TXRQST >> 16;                                           // Now clear out the new data flag.
        CAN_ADDR16(ui32Base + CAN_O_IF2CMD) = ui32ObjID & CAN_IF2CMD_MSG_NUM_M;                                      // Transfer the message object to the message object specified by ui32ObjID.

        while(((CAN_ADDR16(ui32Base + CAN_O_IF2CMD) & \
                CAN_IF2CMD_BUSY) != 0) && (S_Temp < 1000))                                                           // 检查是否处于空闲状态,如果这里通不过，那下面的寄存器都无法操作，因为寄存器都受busy保护
        {
            DELAY_US(1);                                                                                             // 最多等待1ms后退出
            S_Temp++;                                                                                                // 通过做实验，这里在初始化的时候不会进入
        }

        if (S_Temp >= 1000)
        {
            S_Temp = 0;                                                                                              // 退出后将等待计数清理处理
            Rtv = SYS_CAN_OP_ERROR;                                                                                    // 返回CAN接收错误
        }
        else
        {
            S_Temp = 0;
        }

        pMsgObject->ui32Flags |= MSG_OBJ_NEW_DATA;                                                                   // Indicate that there is new data in this message.
    }
    else
    {
//        pMsgObject->ui32MsgLen = 0;                                                                                  // Along with the MSG_OBJ_NEW_DATA not being set the amount of data needs to be set to zero if none was available.
    }
    return (Rtv);                                                                                               // 操作成功
}