TMS320F28335: ECAN使用问题

//###########################################################################
// Description
//! \addtogroup f2833x_example_list
//! <h1>eCAN-A to eCAN-B Trasmit Loop (ecan_a_to_b_xmit)</h1>
//!
//! This example TRANSMITS data to another CAN module using MAILBOX5
//! This program could either loop forever or transmit "n" # of times,
//! where "n" is the TXCOUNT value. \n
//!
//! This example can be used to check CAN-A and CAN-B. Since CAN-B is
//! initialized in DSP2833x_ECan.c, it will acknowledge all frames
//! transmitted by the node on which this code runs. Both CAN ports of
//! the 2833x DSP need to be connected to each other (via CAN transceivers)
//!
//! \b External \b Connections \n
//! - ECanb is on GPIO31 (CANTXA) and GPIO30 (CANRXA)
//! - eCANB is on GPIO8 (CANTXB) and GPIO10 (CANRXB)
//! - Connect ECanb  to eCANB via CAN transceivers
//
//###########################################################################
// $TI Release: F2833x/F2823x Header Files and Peripheral Examples V142 $
// $Release Date: November  1, 2016 $
// $Copyright: Copyright (C) 2007-2016 Texas Instruments Incorporated -
//             http://www.ti.com/ ALL RIGHTS RESERVED $
//###########################################################################

#include "DSP2833x_Device.h"     // DSP2833x Headerfile Include File
#include "DSP2833x_Examples.h"   // DSP2833x Examples Include File

#define TXCOUNT  100  // Transmission will take place (TXCOUNT) times..

// Globals for this example
long      i;
long 	  loopcount = 0;

void main()
{
// Create a shadow register structure for the CAN control registers. This is
// needed, since only 32-bit access is allowed to these registers. 16-bit access
// to these registers could potentially corrupt the register contents or return
// false data.

   struct ECAN_REGS ECanbShadow;

// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the DSP2833x_SysCtrl.c file.
   InitSysCtrl();

// Step 2. Initialize GPIO:
// This example function is found in the DSP2833x_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
// InitGpio();  // Skipped for this example

// Just initialize eCAN pins for this example
// This function is in DSP2833x_ECan.c
   InitECanGpio();

// Step 3. 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.
// This function is found in the DSP2833x_PieCtrl.c file.
   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.
// The shell ISR routines are found in DSP2833x_DefaultIsr.c.
// This function is found in DSP2833x_PieVect.c.
   InitPieVectTable();

// Interrupts that are used in this example are re-mapped to
// ISR functions found within this file.

// No interrupts used in this example.

// Step 4. Initialize all the Device Peripherals:
// This function is found in DSP2833x_InitPeripherals.c
// InitPeripherals(); // Not required for this example

// In this case just initialize eCAN-A and eCAN-B
// This function is in DSP2833x_ECan.c
   InitECan();

// Step 5. User specific code:

/* Write to the MSGID field  */

   ECanbMboxes.MBOX25.MSGID.all = 0x95555555; // Extended Identifier

/* Configure Mailbox under test as a Transmit mailbox */

   ECanbShadow.CANMD.all = ECanbRegs.CANMD.all;
   ECanbShadow.CANMD.bit.MD25 = 0;
   ECanbRegs.CANMD.all = ECanbShadow.CANMD.all;

/* Enable Mailbox under test */

   ECanbShadow.CANME.all = ECanbRegs.CANME.all;
   ECanbShadow.CANME.bit.ME25 = 1;
   ECanbRegs.CANME.all = ECanbShadow.CANME.all;

/* Write to DLC field in Master Control reg */

   ECanbMboxes.MBOX25.MSGCTRL.bit.DLC = 8;

/* Write to the mailbox RAM field */

   ECanbMboxes.MBOX25.MDL.all = 0x01234567;
   ECanbMboxes.MBOX25.MDH.all = 0x89ABCDEF;

/* Begin transmitting */

   for(i=0; i < TXCOUNT; i++)
   {
       ECanbShadow.CANTRS.all = 0;
       ECanbShadow.CANTRS.bit.TRS25 = 1;             // Set TRS for mailbox under test
       ECanbRegs.CANTRS.all = ECanbShadow.CANTRS.all;

       do
       {
      	ECanbShadow.CANTA.all = ECanbRegs.CANTA.all;
       } while(ECanbShadow.CANTA.bit.TA25 != 1 );   // Wait for TA5 bit to be set..


       ECanbShadow.CANTA.all = 0;
       ECanbShadow.CANTA.bit.TA25 = 1;     	         // Clear TA5
       ECanbRegs.CANTA.all = ECanbShadow.CANTA.all;

       loopcount ++;
    }
     __asm(" ESTOP0");  // Stop here
}