LAUNCHXL-F28379D: 如何设置时钟来源

是又有新问题，我在can_external_transmit原例程基础上，单独测试CANB的中断接收程序，can调试器每发送一次can数据（扩展帧 0x5555 Data：01 02 03 04），中断会连续执行两次。第一次中断在执行status = CANIntStatus(CANB_BASE, CAN_INT_STS_CAUSE);时，status 的值 为CAN_INT_INT0ID_STATUS即0x10；

第二次中断，则status的值为RX_MSG_OBJ_ID即1，此时开始执行CANMessageGet(CANB_BASE, RX_MSG_OBJ_ID, &sRXCANMessage, true);

我的判断依据是通过设置计数器变量xx，在中断执行的开头自增一次，只有在执行完CANMessageGet(CANB_BASE, RX_MSG_OBJ_ID, &sRXCANMessage, true);语句后xx清零。

具体代码如下：

//###########################################################################
//
// FILE:   can_external_transmit.c
//
// TITLE:  Example to demonstrate CAN external transmission
//
//! \addtogroup cpu01_example_list
//! <h1>CAN-A to CAN-B External Transmit (can_external_transmit)</h1>
//!
//! This example initializes CAN module A and CAN module B for external
//! communication. CAN-A module is setup to transmit incrementing data for "n"
//! number of times to the CAN-B module, where "n" is the value of TXCOUNT.
//! CAN-B module is setup to trigger an interrupt service routine (ISR) when
//! data is received. An error flag will be set if the transmitted data doesn't
//! match the received data.
//!
//! \note Both CAN modules on the device need to be
//!       connected to each other via CAN transceivers.
//!
//! \b External \b Connections \n
//!  - CANA is on GPIO31 (CANTXA) and GPIO30 (CANRXA)
//!  - CANB is on GPIO8 (CANTXB) and GPIO10 (CANRXB)
//!
//! \b Watch \b Variables \n
//!  - TXCOUNT - Adjust to set the number of messages to be transmitted
//!  - txMsgCount - A counter for the number of messages sent
//!  - rxMsgCount - A counter for the number of messages received
//!  - txMsgData - An array with the data being sent
//!  - rxMsgData - An array with the data that was received
//!  - errorFlag - A flag that indicates an error has occurred
//!
//
//###########################################################################
// $TI Release: F2837xD Support Library v210 $
// $Release Date: Tue Nov  1 14:46:15 CDT 2016 $
// $Copyright: Copyright (C) 2013-2016 Texas Instruments Incorporated -
//             http://www.ti.com/ ALL RIGHTS RESERVED $
//###########################################################################

//
// Included Files
//
#include "F28x_Project.h"     // Device Headerfile and Examples Include File
#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "inc/hw_can.h"
#include "driverlib/can.h"

//
// Defines
//
#define TXCOUNT  100
#define MSG_DATA_LENGTH    4
#define TX_MSG_OBJ_ID    1
#define RX_MSG_OBJ_ID    1

//
// Globals
//
volatile unsigned long i;
volatile uint32_t txMsgCount = 0;
volatile uint32_t rxMsgCount = 0;
volatile uint32_t errorFlag = 0;
unsigned char txMsgData[4];
unsigned char rxMsgData[4];
tCANMsgObject sTXCANMessage;
tCANMsgObject sRXCANMessage;

unsigned char rxdat[4]={0};
unsigned char xx = 0;
//
// Function Prototypes
//
__interrupt void canbISR(void);

//
// Main
//
void main(void)
{
    //
    // Initialize System Control:
    // PLL, WatchDog, enable Peripheral Clocks
    //
    InitSysCtrl();

    //
    // Initialize GPIO and configure GPIO pins for CANTX/CANRX
    // on module A and B
    //
    InitGpio();

    //
    // Setup GPIO pin mux for CAN-A TX/RX and CAN-B TX/RX
    //
    GPIO_SetupPinMux(30, GPIO_MUX_CPU1, 1); //GPIO30 -  CANRXA
    GPIO_SetupPinOptions(30, GPIO_INPUT, GPIO_ASYNC);
    GPIO_SetupPinMux(31, GPIO_MUX_CPU1, 1); //GPIO31 - CANTXA
    GPIO_SetupPinOptions(31, GPIO_OUTPUT, GPIO_PUSHPULL);
    GPIO_SetupPinMux(17, GPIO_MUX_CPU1, 2); //GPIO10 -  CANRXB
    GPIO_SetupPinOptions(17, GPIO_INPUT, GPIO_ASYNC);
    GPIO_SetupPinMux(12, GPIO_MUX_CPU1, 2);  //GPIO8 - CANTXB
    GPIO_SetupPinOptions(12, GPIO_OUTPUT, GPIO_PUSHPULL);

    //
    // Initialize the CAN controllers
    //
    CANInit(CANA_BASE);
    CANInit(CANB_BASE);

    //
    // Setup CAN to be clocked off the PLL output clock
    //
    CANClkSourceSelect(CANA_BASE, 0);   // 500kHz CAN-Clock
    CANClkSourceSelect(CANB_BASE, 0);   // 500kHz CAN-Clock

    //
    // Set up the CAN bus bit rate to 500kHz for each module
    // This function sets up the CAN bus timing for a nominal configuration.
    // You can achieve more control over the CAN bus timing by using the
    // function CANBitTimingSet() instead of this one, if needed.
    // Additionally, consult the device data sheet for more information about
    // the CAN module clocking.
    //
    CANBitRateSet(CANA_BASE, 200000000, 500000);
    CANBitRateSet(CANB_BASE, 200000000, 500000);

    //
    // Enable interrupts on the CAN B peripheral.
    //
    CANIntEnable(CANB_BASE, CAN_INT_MASTER | CAN_INT_ERROR | CAN_INT_STATUS);

    //
    // Clear all interrupts and initialize PIE vector table:
    // Disable CPU interrupts
    //
    DINT;

    //
    // Initialize the PIE control registers to their default state.
    // The default state is all PIE interrupts disabled and flags
    // are cleared.
    //
    InitPieCtrl();

    //
    // Disable CPU interrupts and clear all CPU interrupt flags
    //
    IER = 0x0000;
    IFR = 0x0000;

    //
    // Initialize the PIE vector table with pointers to the shell Interrupt
    // Service Routines (ISR).
    // This will populate the entire table, even if the interrupt
    // is not used in this example.  This is useful for debug purposes.
    //
    InitPieVectTable();

    //
    // Interrupts that are used in this example are re-mapped to
    // ISR functions found within this file.
    // This registers the interrupt handler in PIE vector table.
    //
    EALLOW;
    PieVectTable.CANB0_INT = canbISR;
    EDIS;

    //
    // Enable the CAN-B interrupt on the processor (PIE).
    //
    PieCtrlRegs.PIEIER9.bit.INTx7 = 1;
    IER |= M_INT9;
    EINT;

    //
    // Enable the CAN-B interrupt signal
    //
    CANGlobalIntEnable(CANB_BASE, CAN_GLB_INT_CANINT0);

    //
    // Initialize the transmit message object used for sending CAN messages.
    // Message Object Parameters:
    //      Message Identifier: 0x5555
    //      Message ID Mask: 0x0
    //      Message Object Flags: None
    //      Message Data Length: 4 Bytes
    //      Message Transmit data: txMsgData
    //
    sTXCANMessage.ui32MsgID = 0x5555;
    sTXCANMessage.ui32MsgIDMask = 0;
    sTXCANMessage.ui32Flags = 0;
    sTXCANMessage.ui32MsgLen = MSG_DATA_LENGTH;
    sTXCANMessage.pucMsgData = txMsgData;

    //
    // Initialize the receive message object used for receiving CAN messages.
    // Message Object Parameters:
    //      Message Identifier: 0x5555
    //      Message ID Mask: 0x0
    //      Message Object Flags: Receive Interrupt
    //      Message Data Length: 4 Bytes
    //      Message Receive data: rxMsgData
    //
    sRXCANMessage.ui32MsgID = 0x5555;
    sRXCANMessage.ui32MsgIDMask = 0;
    sRXCANMessage.ui32Flags = MSG_OBJ_RX_INT_ENABLE;
    sRXCANMessage.ui32MsgLen = MSG_DATA_LENGTH;
    sRXCANMessage.pucMsgData = rxMsgData;
    CANMessageSet(CANB_BASE, RX_MSG_OBJ_ID, &sRXCANMessage,
                  MSG_OBJ_TYPE_RX);

    //
    // Initialize the transmit message object data buffer to be sent
    //
    txMsgData[0] = 0x12;
    txMsgData[1] = 0x34;
    txMsgData[2] = 0x56;
    txMsgData[3] = 0x78;

    //
    // Start CAN module A and B operations
    //
    CANEnable(CANA_BASE);
    CANEnable(CANB_BASE);

    //
    // Transmit messages from CAN-A to CAN-B
    //
//    for(i = 0; i < TXCOUNT; i++)
    for( ;  ;  )
    {
        //
        // Check the error flag to see if errors occurred
        //
        /*if(errorFlag)
        {
            asm("   ESTOP0");
        }*/

        //
        // Verify that the number of transmitted messages equal the number of
        // messages received before sending a new message
        //
       /* if(txMsgCount == rxMsgCount)
        {*/
            //
            // Transmit Message
            //
            CANMessageSet(CANA_BASE, TX_MSG_OBJ_ID, &sTXCANMessage,
                          MSG_OBJ_TYPE_TX);

        /*    txMsgCount++;
        }*/
        /*else
        {
            errorFlag = 1;
        }*/

        //
        // Delay 0.25 second before continuing
        //
        DELAY_US(1000 * 250);

        //
        // Increment the value in the transmitted message data.
        //
        txMsgData[0] += 0x01;
        txMsgData[1] += 0x01;
        txMsgData[2] += 0x01;
        txMsgData[3] += 0x01;
    }

    //
    // Stop application
    //
    asm("   ESTOP0");
}

//
// CAN B ISR - The interrupt service routine called when a CAN interrupt is
//             triggered on CAN module B.
//
__interrupt void
canbISR(void)
{
    uint32_t status;
    int i=0;
    xx++;
    //
    // Read the CAN-B interrupt status to find the cause of the interrupt
    //
    status = CANIntStatus(CANB_BASE, CAN_INT_STS_CAUSE);

    //
    // If the cause is a controller status interrupt, then get the status
    //
    if(status == CAN_INT_INT0ID_STATUS)
    {
        //
        // Read the controller status.  This will return a field of status
        // error bits that can indicate various errors.  Error processing
        // is not done in this example for simplicity.  Refer to the
        // API documentation for details about the error status bits.
        // The act of reading this status will clear the interrupt.
        //
        status = CANStatusGet(CANB_BASE, CAN_STS_CONTROL);
//        CANMessageGet(CANB_BASE, RX_MSG_OBJ_ID, &sRXCANMessage, true);

        //
        // Check to see if an error occurred.
        //
        if(((status  & ~(CAN_ES_RXOK)) != 7) &&
           ((status  & ~(CAN_ES_RXOK)) != 0))
        {
            //
            // Set a flag to indicate some errors may have occurred.
            //
            errorFlag = 1;
        }
    }
    //
    // Check if the cause is the CAN-B receive message object 1
    //
    else if(status == RX_MSG_OBJ_ID)
    {
        //
        // Get the received message
        //
        CANMessageGet(CANB_BASE, RX_MSG_OBJ_ID, &sRXCANMessage, true);
        for(i = 0;i < 4;i++)
        {
            rxdat[i] = sRXCANMessage.pucMsgData[i];
        }
        xx = 0;
        //
        // Getting to this point means that the RX interrupt occurred on
        // message object 1, and the message RX is complete.  Clear the
        // message object interrupt.
        //
        CANIntClear(CANB_BASE, RX_MSG_OBJ_ID);

        //
        // Increment a counter to keep track of how many messages have been
        // received. In a real application this could be used to set flags to
        // indicate when a message is received.
        //
        rxMsgCount++;

        //
        // Since the message was received, clear any error flags.
        //
        errorFlag = 0;
    }
    //
    // If something unexpected caused the interrupt, this would handle it.
    //
    else
    {
        //
        // Spurious interrupt handling can go here.
        //
    }

    //
    // Clear the global interrupt flag for the CAN interrupt line
    //
    CANGlobalIntClear(CANB_BASE, CAN_GLB_INT_CANINT0);

    //
    // Acknowledge this interrupt located in group 9
    //
    PieCtrlRegs.PIEACK.all = PIEACK_GROUP9;
}

//
// End of File
//

仿真截图，当程序执行到CANMessageGet函数时，xx和data里的数据