TMS320F28335: How do I use RS232 cable with this DSP

Hi Marcus,

The Example_2833xSci_Echoback is intended to be ran with the SCI-A and PC. Do you see anything in the terminal? Are you using the correct COM port? 

Best Regards,

Marlyn

Hi Marlyn,

Sorry on my part I was not paying attention on the example, how about the Example_2833xSci_Autobaud program? It says to connect it to the GPIO pins but how am I able to use the RS232 cable to do that?

Best Rgds,
Marcus

Hi Marcus,

To connect SCI-A (RS232 connection) with the SCI-B (header pins) you will probably need to strip an RS232 cable and form the connection yourself. 

Is your end goal communication between SCI-A and SCI-B or is it with another device?

Best Regards,

Marlyn

Hi Marlyn,
Yes my end goal is communication between SCI-A and SCI-B. I already have a RS232 connector and a 5x2 pin header for the connection, however I am unsure about how to configure the software.
Do I have to configure the SCI.c file or other relevant files?

Best Rgds,
Marcus

Hi Marcus, 

To get started with the software, you can take a look at the Example_2833xSci_Autobaud program. This example was designed for our other hardware evaluation modules such as the F28335 controlCARD and that is why it references GPIOs. As long as you have the proper connection between SCI-A and SCI-B (which it seems like you do), the example should work. What happens when you run that example?

Best Regards,

Marlyn

Hi Marlyn,

When the example is in the debug terminal, the registers page does not shows SCIA and SCIB's Tx and Rx moving.
Would like to check with you for the ezdsp F28335 J12 which is SCIB the GPIO pins are 9 and 11?

Best Rgds,
Marcus

Hi Marcus,

Yes, if you have SW2 still in the default state, SCIB should be GPIOs 9/11. The example uses GPIOs 18/19, for SCIB, you'll have to change this to GPIOs 9 and 11. This can be done in the InitScibGpio() function.

Best Regards,

Marlyn

Hi Marlyn,

I have configured the above as you mentioned however when I tried to run the program it directly brings me to 

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

Is there any fix for this problem?

Best Rgds,
Marcus

//###########################################################################
// 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.
//===========================================================================

Also here is the coding for my program, I did not make much changes to it. I also configured the InitScibGpio to 9 and 11. 

Update: When the RS232 cable is plugged into P12 and J12 it goes straight to void error(). Could there be something wrong with the RS232 cable?

Thank You.

Hi Marcus,

What is the status of the registers when you come across the error? 

Marcus Ong said:

Update: When the RS232 cable is plugged into P12 and J12 it goes straight to void error(). Could there be something wrong with the RS232 cable?

A way to test this would be to use the other SCI pins on the board. I believe J2 and J4 also bring out the SCI pins. This will be through different GPIOs so you'll have to change that in your code but I would try running the example in that way first.

Best Regards,

Marlyn

Hi Marlyn,
The registers for SCIA and SCIB are empty and it is not moving.

I am using a ezdsp F28335 and I couldn't seem to find a J2 and J4 to test the RS232 cable. Are there other solutions?

Best Regards,
Marcus