[参考译文] TMS320F28335：如何将 RS232电缆与此 DSP 配合使用

//###########################################################################
// Description:
//! \addtogroup f2833x_example_list
//! <h1>SCI Autobaud (sci_autobaud)</h1>
//!
//! This test will perform autobaud lock at a variety of baud rates, including
//! very high baud rates.
//!
//! For this test to properly run, connect the SCI-A pins to the
//! SCI-B pins without going through a transceiver.
//! At higher baud rates, the slew rate of the incoming data bits can be
//! affected by transceiver and connector performance. This slew rate may
//! limit reliable autobaud detection at higher baud rates.
//!
//! SCIA: Slave, autobaud locks, receives characters and
//! echos them back to the host.  Uses the RX interrupt
//! to receive characters.
//!
//! SCIB: Host, known baud rate, sends characters to the slave
//! and checks that they are echoed back.
//!
//! \b External \b Connections \n
//! - SCITXDA is on GPIO29
//! - SCIRXDB is on GPIO19 - 11
//! - SCIRXDA is on GPIO28
//! - SCITXDB is on GPIO18 - 9
//! - Connect GPIO29 to GPIO19 - Changed 19 to 11
//! - Connect GPIO28 to GPIO18 - Changed 18 to 9
//!
//! \b Watch \b Variables \n
//! - BRRVal            - current BRR value used for SCIB
//! - ReceivedAChar     - character received by SCIA
//! - ReceivedBChar     - character received by SCIB
//! - SendChar          - character being sent by SCIB
//! - SciaRegs.SCILBAUD - SCIA baud register set by autobaud lock
//! - SciaRegs.SCIHBAUD - SCIA baud register set by autobaud lock
//
//
//###########################################################################
// $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 "DSP28x_Project.h"     // Device Headerfile and Examples Include File
#include "DSP2833x_Gpio.h"
#define BAUDSTEP 100            // Amount BRR will be incremented between each
                                // autobaud lock

// Prototype statements for functions found within this file.
void scia_init(void);
void scib_init(void);
void scia_xmit(int a);
void scib_xmit(int a);
void scia_AutobaudLock(void);
void error();
__interrupt void rxaint_isr(void);

// Global counts used in this example
Uint16 LoopCount;
//Uint16 xmitCount;
Uint16 ReceivedCount;
Uint16 ErrorCount;
Uint16 SendChar;
Uint16 ReceivedAChar;   // scia received character
Uint16 ReceivedBChar;   // scib received character
Uint16 BRRVal;
Uint16 Buff[10] = {0x55, 0xAA, 0xF0, 0x0F, 0x00, 0xFF, 0xF5, 0x5F, 0xA5, 0x5A};

void main(void)
{
   Uint16 i;

// 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

   InitSciGpio();
   //InitScibGpio();


// Initialize 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.
   EALLOW;      // This is needed to write to EALLOW protected registers
   PieVectTable.SCIRXINTA = &rxaint_isr;
   EDIS;       // This is needed to disable write to EALLOW protected register

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

// Step 5. User specific code, enable interrupts:
   LoopCount = 0;
   ErrorCount = 0;

// Enable interrupts
   PieCtrlRegs.PIEIER9.all = 0x0001; // Enable all SCIA RXINT interrupt
   IER |= 0x0100;                    // enable PIEIER9, and INT9
   EINT;

    // Start with BRR = 1, work through each baud rate setting
    // incrementing BRR by BAUDSTEP
    for (BRRVal = 0x0000; BRRVal < (Uint32)0xFFFF; BRRVal+=BAUDSTEP)
    {
        // SCIB has a known baud rate.  SCIA will autobaud to match
        ScibRegs.SCIHBAUD = (BRRVal >> 8);
        ScibRegs.SCILBAUD = (BRRVal);

        // Initiate an autobaud lock with scia.  Check
        // returned character against baud lock character 'A'
        scia_AutobaudLock();
        while(ScibRegs.SCIRXST.bit.RXRDY != 1) { }
        ReceivedBChar = 0;
        ReceivedBChar =  ScibRegs.SCIRXBUF.bit.RXDT;
        if(ReceivedBChar != 'A')
        {
            error(0);
        }

        // Send/echoback characters
        // 55 AA F0 0F 00 FF F5 5F A5 5A
        for(i= 0; i<=9; i++)
        {
          SendChar = Buff[i];
          scib_xmit(SendChar);              // Initiate interrupts and xmit data in isr
          // Wait to get the character back and check
          // against the sent character.
          while(ScibRegs.SCIRXST.bit.RXRDY != 1)
          {
              __asm("   NOP");
          }
          ReceivedBChar = 0;
          ReceivedBChar =  ScibRegs.SCIRXBUF.bit.RXDT;
          if(ReceivedBChar != SendChar) error(1);
        }

    } // Repeat for next BRR setting

    // Stop here, no more
    for(;;)
    {
       __asm("    NOP");
    }
}

/* --------------------------------------------------- */
/* ISR for PIE INT9.1                                  */
/* Connected to RXAINT  SCI-A                          */
/* ----------------------------------------------------*/

__interrupt void rxaint_isr(void)     // SCI-A
{
  // Insert ISR Code here

   PieCtrlRegs.PIEACK.all = PIEACK_GROUP9;

   // If autobaud detected, we must clear CDC
   if(SciaRegs.SCIFFCT.bit.ABD == 1)
   {
      SciaRegs.SCIFFCT.bit.ABDCLR = 1;
      SciaRegs.SCIFFCT.bit.CDC = 0;
      // Check received character - should be 'A'
      ReceivedAChar = 0;
      ReceivedAChar = SciaRegs.SCIRXBUF.all;
      if(ReceivedAChar != 'A')
      {
         error(2);
      }
      else scia_xmit(ReceivedAChar);
   }

   // This was not autobaud detect
   else
   {
      // Check received character against sendchar
      ReceivedAChar = 0;
      ReceivedAChar = SciaRegs.SCIRXBUF.all;
      if(ReceivedAChar != SendChar)
      {
         error(3);
      }
      else scia_xmit(ReceivedAChar);
   }

   SciaRegs.SCIFFRX.bit.RXFFINTCLR = 1; // clear Receive interrupt flag
   ReceivedCount++;
}

void error()
{
      ErrorCount++;
      __asm("     ESTOP0");            // Uncomment to stop the test here
      for (;;);
}

// SCIA  8-bit word, baud rate 0x000F, default, 1 STOP bit, no parity
void scia_init()
{
    // Note: Clocks were turned on to the SCIA peripheral
    // in the InitSysCtrl() function

    // Reset FIFO's
    SciaRegs.SCIFFTX.all=0x8000;

    SciaRegs.SCICCR.all =0x0007;   // 1 stop bit,  No loopback
                                   // No parity,8 char bits,
                                   // async mode, idle-line protocol
    SciaRegs.SCICTL1.all =0x0003;  // enable TX, RX, internal SCICLK,
                                   // Disable RX ERR, SLEEP, TXWAKE
    SciaRegs.SCICTL2.all =0x0003;
    SciaRegs.SCICTL2.bit.RXBKINTENA =1;
    SciaRegs.SCICTL1.all =0x0023;     // Relinquish SCI from Reset

    return; // i added this line
}

// SCIB  8-bit word, baud rate 0x000F, default, 1 STOP bit, no parity

void scib_init()
{
    // Reset FIFO's
    ScibRegs.SCIFFTX.all=0x8000;

    // 1 stop bit, No parity, 8-bit character
    // No loopback
    ScibRegs.SCICCR.all = 0x0007;

    // Enable TX, RX, Use internal SCICLK
    ScibRegs.SCICTL1.all = 0x0003;

    // Disable RxErr, Sleep, TX Wake,
    // Disable Rx Interrupt, Tx Interrupt
    ScibRegs.SCICTL2.all = 0x0000;

    // Relinquish SCI-A from reset
    ScibRegs.SCICTL1.all = 0x0023;

    return;
}

// Transmit a character from the SCI-A'
void scia_xmit(int a)
{
    SciaRegs.SCITXBUF=a;
}

// Transmit a character from the SCI-B'
void scib_xmit(int a)
{
    ScibRegs.SCITXBUF=a;
}

//------------------------------------------------
// Perform autobaud lock with the host.
// Note that if autobaud never occurs
// the program will hang in this routine as there
// is no timeout mechanism included.
//------------------------------------------------
void scia_AutobaudLock()
{

    SciaRegs.SCICTL1.bit.SWRESET = 0;
    SciaRegs.SCICTL1.bit.SWRESET = 1;

    // Must prime baud register with >= 1
    SciaRegs.SCIHBAUD = 0;
    SciaRegs.SCILBAUD = 1;

    // Prepare for autobaud detection
    // Make sure the ABD bit is clear by writing a 1 to ABDCLR
    // Set the CDC bit to enable autobaud detection
    SciaRegs.SCIFFCT.bit.ABDCLR = 1;
    SciaRegs.SCIFFCT.bit.CDC = 1;

    // Wait until we correctly read an
    // 'A' or 'a' and lock
    //
    // As long as Autobaud calibration is enabled (CDC = 1),
    // SCI-B (host) will continue transmitting 'A'. This will
    // continue until interrupted by the SCI-A RX ISR, where
    // SCI-A RXBUF receives 'A', autobaud-locks (ABDCLR=1
    // CDC=0),and returns an 'A' back to the host. Then control
    // is returned to this loop and the loop is exited.
    //
    // NOTE: ABD will become set sometime between
    //       scib_xmit and the DELAY_US loop, and
    //       the SCI-A RX ISR will be triggered.
    //       Upon returning and reaching the if-statement,
    //       ABD will have been cleared again by the ISR.

    while(SciaRegs.SCIFFCT.bit.CDC== 1)
    {
       // Note the lower the baud rate the longer
       // this delay has to be to allow the other end
       // to echo back a character (about 4 characters long)
       // Make this really long since we are going through all
       // the baud rates.
       DELAY_US(280000L);

       if(SciaRegs.SCIFFCT.bit.CDC == 1)
           scib_xmit('A');  // host transmits 'A'
   }

    return;
}



//===========================================================================
// No more.
//===========================================================================