LAUNCHXL-F280049C: About interrupt line 1(CAN1INT) in CAN module

//#############################################################################
//
// FILE:   can_ex2_loopback_interrupts.c
//
// TITLE:   CAN External Loopback with Interrupts Example
//
//! \addtogroup driver_example_list
//! <h1> CAN External Loopback with Interrupts </h1>
//!
//! This example shows the basic setup of CAN in order to transmit and receive
//! messages on the CAN bus.  The CAN peripheral is configured to transmit
//! messages with a specific CAN ID.  A message is then transmitted once per
//! second, using a simple delay loop for timing.  The message that is sent is
//! a 4 byte message that contains an incrementing pattern.  A CAN interrupt
//! handler is used to confirm message transmission and count the number of
//! messages that have been sent.
//!
//! This example sets up the CAN controller in External Loopback test mode.
//! Data transmitted is visible on the CANTXA/CANATX pin and is received internally
//! back to the CAN Core.
//!
//! \b External \b Connections \n
//!  - None.
//!
//! \b Watch \b Variables \n
//!  - 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: F28004x Support Library v1.11.00.00 $
// $Release Date: Sun Oct  4 15:49:15 IST 2020 $
// $Copyright:
// Copyright (C) 2020 Texas Instruments Incorporated - http://www.ti.com/
//
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// modification, are permitted provided that the following conditions 
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// 
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//   distribution.
// 
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// $
//#############################################################################

//
// Included Files
//
#include "driverlib.h"
#include "device.h"

//
// Defines
//
#define MSG_DATA_LENGTH    4
#define TX_MSG_OBJ_ID      1
#define RX_MSG_OBJ_ID      2

//
// Globals
//
volatile uint32_t txMsgCount = 0;
volatile uint32_t rxMsgCount = 0;
volatile uint32_t errorFlag = 0;
uint16_t txMsgData[4];
uint16_t rxMsgData[4];

//
// Function Prototypes
//
__interrupt void canISR(void);

//
// Main
//
void main(void)
{
    //
    // Initialize device clock and peripherals
    //
    Device_init();

    //
    // Initialize GPIO and configure GPIO pins for CANTX/CANRX
    //
    Device_initGPIO();
    GPIO_setPinConfig(DEVICE_GPIO_CFG_CANRXA);
    GPIO_setPinConfig(DEVICE_GPIO_CFG_CANTXA);

    //
    // Initialize the CAN controller
    //
    CAN_initModule(CANA_BASE);

    //
    // Set up the CAN bus bit rate to 500kHz
    // Refer to the Driver Library User Guide for information on how to set
    // tighter timing control. Additionally, consult the device data sheet
    // for more information about the CAN module clocking.
    //
    CAN_setBitRate(CANA_BASE, DEVICE_SYSCLK_FREQ, 500000, 20);

    //
    // Enable interrupts on the CAN peripheral.
    //
    CAN_enableInterrupt(CANA_BASE, CAN_INT_IE0 | CAN_INT_ERROR |
                        CAN_INT_STATUS);

    //
    // Initialize PIE and clear PIE registers. Disables CPU interrupts.
    //
    Interrupt_initModule();

    //
    // Initialize the PIE vector table with pointers to the shell Interrupt
    // Service Routines (ISR).
    //
    Interrupt_initVectorTable();

    //
    // Enable Global Interrupt (INTM) and realtime interrupt (DBGM)
    //
    EINT;
    ERTM;

    //
    // 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.
    //
    Interrupt_register(INT_CANA1, &canISR);

    //
    // Enable the CAN interrupt signal
    //
    Interrupt_enable(INT_CANA1);
    CAN_enableGlobalInterrupt(CANA_BASE, CAN_GLOBAL_INT_CANINT1);
    HWREG(CANA_BASE + CAN_O_IP_MUX21) = 0xFFFFFFFF;

    //
    // Enable CAN test mode with external loopback
    //
    CAN_enableTestMode(CANA_BASE, CAN_TEST_EXL);

    //
    // Initialize the transmit message object used for sending CAN messages.
    // Message Object Parameters:
    //      Message Object ID Number: 1
    //      Message Identifier: 0x1
    //      Message Frame: Standard
    //      Message Type: Transmit
    //      Message ID Mask: 0x0
    //      Message Object Flags: Transmit Interrupt
    //      Message Data Length: 4 Bytes
    //
    CAN_setupMessageObject(CANA_BASE, TX_MSG_OBJ_ID, 0x1, CAN_MSG_FRAME_STD,
                           CAN_MSG_OBJ_TYPE_TX, 0, CAN_MSG_OBJ_TX_INT_ENABLE,
                           MSG_DATA_LENGTH);

    //
    // Initialize the receive message object used for receiving CAN messages.
    // Message Object Parameters:
    //      Message Object ID Number: 2
    //      Message Identifier: 0x1
    //      Message Frame: Standard
    //      Message Type: Receive
    //      Message ID Mask: 0x0
    //      Message Object Flags: Receive Interrupt
    //      Message Data Length: 4 Bytes
    //
    CAN_setupMessageObject(CANA_BASE, RX_MSG_OBJ_ID, 0x1, CAN_MSG_FRAME_STD,
                           CAN_MSG_OBJ_TYPE_RX, 0, CAN_MSG_OBJ_RX_INT_ENABLE,
                           MSG_DATA_LENGTH);

    //
    // 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 operations
    //
    CAN_startModule(CANA_BASE);

    //
    // Loop Forever - A new message will be sent once per second.
    //
    for(;;)
    {
        //
        // Check the error flag to see if errors occurred
        //
        if(errorFlag)
        {
            Example_Fail = 1;
            asm("   ESTOP0");
        }

        //
        // Verify that the number of transmitted messages equal the number of
        // messages received before sending a new message
        //
        if(txMsgCount == rxMsgCount)
        {
            CAN_sendMessage(CANA_BASE, TX_MSG_OBJ_ID, MSG_DATA_LENGTH,
                            txMsgData);

            Example_PassCount++;
        }
        else
        {
            errorFlag = 1;
        }

        //
        // Delay 1 second before continuing
        //
        DEVICE_DELAY_US(1000000);

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

        //
        // Reset data if exceeds a byte
        //
        if(txMsgData[0] > 0xFF)
        {
            txMsgData[0] = 0;
        }
        if(txMsgData[1] > 0xFF)
        {
            txMsgData[1] = 0;
        }
        if(txMsgData[2] > 0xFF)
        {
            txMsgData[2] = 0;
        }
        if(txMsgData[3] > 0xFF)
        {
            txMsgData[3] = 0;
        }
    }
}

//
// CAN ISR - The interrupt service routine called when a CAN interrupt is
//           triggered.  It checks for the cause of the interrupt, and
//           maintains a count of all messages that have been transmitted.
//
__interrupt void
canISR(void)
{
    uint32_t status;

    //
    // Read the CAN interrupt status to find the cause of the interrupt
    //
    status = CAN_getInterruptCause(CANA_BASE);

    //
    // 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 = CAN_getStatus(CANA_BASE);

        //
        // Check to see if an error occurred.
        //
        if(((status  & ~(CAN_STATUS_TXOK | CAN_STATUS_RXOK)) != 7) &&
           ((status  & ~(CAN_STATUS_TXOK | CAN_STATUS_RXOK)) != 0))
        {
            //
            // Set a flag to indicate some errors may have occurred.
            //
            errorFlag = 1;
        }
    }

    //
    // Check if the cause is the transmit message object 1
    //
    else if(status == TX_MSG_OBJ_ID)
    {
        //
        // Getting to this point means that the TX interrupt occurred on
        // message object 1, and the message TX is complete.  Clear the
        // message object interrupt.
        //
        CAN_clearInterruptStatus(CANA_BASE, TX_MSG_OBJ_ID);

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

        //
        // Since the message was sent, clear any error flags.
        //
        errorFlag = 0;
    }

    //
    // Check if the cause is the receive message object 2
    //
    else if(status == RX_MSG_OBJ_ID)
    {
        //
        // Get the received message
        //
        CAN_readMessage(CANA_BASE, RX_MSG_OBJ_ID, rxMsgData);

        //
        // Getting to this point means that the RX interrupt occurred on
        // message object 2, and the message RX is complete.  Clear the
        // message object interrupt.
        //
        CAN_clearInterruptStatus(CANA_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
    //
    CAN_clearGlobalInterruptStatus(CANA_BASE, CAN_GLOBAL_INT_CANINT1);

    //
    // Acknowledge this interrupt located in group 9
    //
    Interrupt_clearACKGroup(INTERRUPT_ACK_GROUP9);
}

//
// End of File
//