CCS/TMS320F28335: SCI communication between tms320 and arduino results in garbage data

Mohit Singh1

Part Number: TMS320F28335
Other Parts Discussed in Thread: C2000WARE

Tool/software: Code Composer Studio

Hi,

I have a custom TMS320F28335 board with which I am trying to communicate with an arduino mega using SCI/UART interface.

I am sending 10 data bytes from arduino and trying to receive and see them in debug mode in CCS.I am putting a breakpoint at j=0 line and to see the data so far collected. which should be 10 bytes of data that is collected. At the arduino side the code is continously sending numbers 1234567890. What I am receiving in the expressions window when I check Received char array is bunch of random numbers. sometimes i get the correct sequence in between but mostly I see random data. Can anyone point to me what is the mistake that I am doing.

My code is as follows:

#include "DSP28x_Project.h"
void scic_regs_init(void);
void scic_fifo_init(void);

int j=0;
int k =0;
void main(void)
{
    char ReceivedChar[10];

    InitSysCtrl();
    InitSci();
    DINT;
    IER = 0x0000;
    IFR = 0x0000;
    InitPieVectTable();
    EnableInterrupts();
    scic_regs_init();  // Initialize SCI for echoback
    scic_fifo_init();      // Initialize the SCI FIFO
while(1)
{
   while(!ScicRegs.SCIFFRX.bit.RXFFST ){}


   ReceivedChar[j++] = (ScicRegs.SCIRXBUF.bit.RXDT);
   for(k=0;k<100;k++);

   if(j==10)
{
   j=0;
}
}



}




void scic_regs_init()
{
    // Note: Clocks were turned on to the SCIA peripheral
    // in the InitSysCtrl() function

    ScicRegs.SCICCR.bit.rsvd1=0;
    ScicRegs.SCICCR.bit.STOPBITS=0;  // 1 stop bit
    ScicRegs.SCICCR.bit.PARITY=0;
    ScicRegs.SCICCR.bit.PARITYENA=0; //no parity
    ScicRegs.SCICCR.bit.LOOPBKENA=0; //disable digital loopback
    ScicRegs.SCICCR.bit.ADDRIDLE_MODE=0;
    ScicRegs.SCICCR.bit.SCICHAR=0x07; //8 bit

    ScicRegs.SCICTL1.bit.rsvd=0;
    ScicRegs.SCICTL1.bit.rsvd1=0;
    ScicRegs.SCICTL1.bit.RXERRINTENA=0; //disable rx interrupt
    ScicRegs.SCICTL1.bit.SWRESET=0; // apply sci sw reset
    ScicRegs.SCICTL1.bit.TXWAKE=0;
    ScicRegs.SCICTL1.bit.SLEEP=0; //sleep mode disabled
    ScicRegs.SCICTL1.bit.TXENA=1;  //enable tx
    ScicRegs.SCICTL1.bit.RXENA=1;  // enable rx

    ScicRegs.SCICTL2.bit.rsvd=0;
    ScicRegs.SCICTL2.bit.rsvd1=0;
    ScicRegs.SCICTL2.bit.TXRDY=0;
    ScicRegs.SCICTL2.bit.TXEMPTY=0;
    ScicRegs.SCICTL2.bit.RXBKINTENA =0;
    ScicRegs.SCICTL2.bit.TXINTENA =1;


    ScicRegs.SCIHBAUD    =0x0000;  // 115200 baud @LSPCLK = 37.5MHz.
    ScicRegs.SCILBAUD    =0x0027;

    ScicRegs.SCICTL1.bit.SWRESET=1;// Relinquish SCI from Reset by setting SWRESET =1

    ScicRegs.SCIPRI.bit.FREE=0;
    ScicRegs.SCIPRI.bit.SOFT=1;
}

void scic_fifo_init()
{

    ScicRegs.SCIFFTX.bit.SCIRST=1;
    ScicRegs.SCIFFTX.bit.SCIFFENA=1;
    ScicRegs.SCIFFTX.bit.TXFIFOXRESET=1;
    ScicRegs.SCIFFTX.bit.TXFFST=0;
    ScicRegs.SCIFFTX.bit.TXFFINT=0;
    ScicRegs.SCIFFTX.bit.TXFFINTCLR=1;
    ScicRegs.SCIFFTX.bit.TXFFIENA=0;
    ScicRegs.SCIFFTX.bit.TXFFIL=0;

    ScicRegs.SCIFFRX.all=0x205f;

    ScicRegs.SCIFFCT.all=0x0;
}

over 5 years ago

0 Yashwant Temburu1 over 5 years ago

TI__Expert 4145 points

Hi Mohit,

Can you check if the sci echoback example is working? (C2000Ware_3_03_00_00\device_support\f2833x\examples\sci_echoback in C2000Ware)

In your code you are not initializing the gpio InitSciaGpio() which uses GPIO 28, 29 for RX TX. InitSci() is not predefined, it is an empty function which has to be filled.

What is the CPU frequency of your custom board? Based on the CPU frequency the SCIHBAUD and SCILBAUD values will change. For example for 9600 baud rate following are the values based on the CPU frequency. You can try using the following values and set the communication baud rate in both devices to 9600 to see if the baud parameters are the issue.

#if (CPU_FRQ_150MHZ)
SciaRegs.SCIHBAUD =0x0001; // 9600 baud @LSPCLK = 37.5MHz.
SciaRegs.SCILBAUD =0x00E7;
#endif
#if (CPU_FRQ_100MHZ)
SciaRegs.SCIHBAUD =0x0001; // 9600 baud @LSPCLK = 20MHz.
SciaRegs.SCILBAUD =0x0044;
#endif

Thanks,

Yashwant

0 Mohit Singh1 over 5 years ago in reply to Yashwant Temburu1

Prodigy 215 points

Hi,

Thanks for the response.

I am initialising the SCI-C channel that I am using inside the InitSci() function. I know I have initialised it correctly as I am able to receive single characters when I send them from arduino side.

while(1)
     {

         ff_st = ScicRegs.SCIFFRX.bit.RXFFST;

        if(ff_st== 16)
        {
            for(j=0;j<16;j++)
            {
            ReceivedChar[j] = (ScicRegs.SCIRXBUF.bit.RXDT);
            for(k=0;k<100;k++);
            }
            if(j==16)
            {
                j=0;
            }

        }

When I use the above code, I am able to receive the data correctly when i send a large bit sequence from arduino. For example if i send 'Hi My Name is Mohit", i receive "Hi My Name is Mo" which is expected as the size of my buffer is 16 bits.

But when I send a continous stream of data from arduino in a loop I don't get any correct character in my ReceivedChar array.

In my mind both the conditions should give the same behavior.. The buffer should fill up 16 characters and ignore the rest.. But this is not happening.

My board is 150MHz based and I have calculated the values for BRR according to that.

I will check the SCI echoback code and update here.

0 Yashwant Temburu1 over 5 years ago in reply to Mohit Singh1

TI__Expert 4145 points

Before reading the receive data can you put a check for an error in the receive data. SCIRXST register shows the possible errors while receivng.

If there is any error, perform a software reset. ScicRegs.SCICTL1.bit.SWRESET=0; ScicRegs.SCICTL1.bit.SWRESET=1;

Regards,

Yashwant

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CCS/TMS320F28335: SCI communication between tms320 and arduino results in garbage data