TMS320F280025C: Using LIN as UART to serially transmit data

Hi Vince,

Thanks for your reply.

As you had suggested, I went through "lin_ex7_external_loopback.c" example in C2000Ware. This example operates in LIN mode and not in SCI-compatible mode, but it did help me understand the LIN module better. Now I do have a partially working code, but the characters printed it the terminal are not as expected.

After debugging, I was able to observe the correct data in the transmit buffer (SCITD) but the data received in the terminal is corrupted. I am assuming this has something to do with the transmitter shift register (SCITXSHF).

I am attaching the code as well as the screenshots of the registers and terminal window for your ready reference.

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

//
// Defines
//
#define CHAR_LENGTH     8
#define FRAME_LENGTH    1

//
// Configure the Baud Rate to 115.207kHz
//
uint32_t PRESCALER=0x000001a;
uint16_t DIVIDER=0x0002;

//
// Globals
//
uint16_t data[] = {'H','e','l','l','o',' ','W','o','r','l','d'};
uint16_t i;

//
// Function Prototypes
//
void configureSCIMode(void);

//
// Main
//
void main(void)
{
    uint16_t len = strlen(data);

    //
    // Initialize device clock and peripherals
    //
    Device_init();

    //
    // Initialize GPIO and configure GPIO pins for LINTX/LINRX
    //
    Device_initGPIO();

    //
    // 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();

    //
    // Configure GPIO pins.
    //
    GPIO_setPinConfig(DEVICE_GPIO_CFG_LINTXA);
    GPIO_setDirectionMode(DEVICE_GPIO_PIN_LINTXA, GPIO_DIR_MODE_OUT);
    GPIO_setPadConfig(DEVICE_GPIO_PIN_LINTXA, GPIO_PIN_TYPE_STD);
    GPIO_setQualificationMode(DEVICE_GPIO_PIN_LINTXA, GPIO_QUAL_ASYNC);

    //
    // Initialize the LIN module
    //
    LIN_initModule(LINA_BASE);

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

    //
    // Configure the LIN module to operate in SCI mode
    //
    configureSCIMode();

    for(i=0;i<len;i++)
    {
        //
        // Write data to Tx Buffer of LINA
        //
        LIN_writeSCICharBlocking(LINA_BASE, data[i]);

        //
        // Wait until Transmit buffer is empty and has completed transmission
        //
        while(!LIN_isTxBufferEmpty(LINA_BASE));

        DEVICE_DELAY_US(10000);  //10ms delay
    }

    //
    // Example completed.
    //
    asm("   ESTOP0");
}

//
// Configure SCI Mode - This function configures the LIN module to operate as
// an SCI with the specified settings.
//
void
configureSCIMode(void)
{
    //
    // Enter LIN reset state to perform configurations
    //
    LIN_enterSoftwareReset(LINA_BASE);

    //
    // Enable Transmit Data Transfer.
    //
    LIN_enableDataTransmitter(LINA_BASE);

    //
    // Switch LIN into SCI mode
    //
    LIN_enableSCIMode(LINA_BASE);

    //
    // Set the SCI communication mode to idle line
    //
    LIN_setSCICommMode(LINA_BASE, LIN_COMM_SCI_IDLELINE);

    //
    // Set SCI to transmit one stop bit
    //
    LIN_setSCIStopBits(LINA_BASE,LIN_SCI_STOP_ONE);

    //
    // Disable parity check
    //
    LIN_disableSCIParity(LINA_BASE);

    //
    // Disable multi-buffer mode
    //
    LIN_disableMultibufferMode(LINA_BASE);

    //
    // Module set to complete operations when halted by debugger
    //
    LIN_setDebugSuspendMode(LINA_BASE, LIN_DEBUG_COMPLETE);

    //
    // Set character length as 8-bits
    //
    LIN_setSCICharLength(LINA_BASE, CHAR_LENGTH);

    //
    // Set to 1 character in response field
    //
    LIN_setSCIFrameLength(LINA_BASE, FRAME_LENGTH);

    //
    // Set the Baud Rate
    //
    LIN_setBaudRatePrescaler(LINA_BASE, PRESCALER, DIVIDER);

    //
    // Exit LIN reset state
    //
    LIN_exitSoftwareReset(LINA_BASE);
}

//
// End of File
//

Please let me know your thoughts on this issue.

Also, thank you for answering the other question. I would also like to know whether the data transmitted and received in SCI-compatible mode of LIN is in the FIFO format or LIFO format?

Thank you and regards,

Mahesh

Hi Mahesh,

It looks like the LIN is sending 8 bit words, but the terminal is expecting 16 bit words (notice how each byte in the terminal has "F"). Can you show your terminal settings?

Regards,

Vince

Hi Vince,

Here are the terminal settings you requested.

Apart from this, the display mode is set to "hex" for the time being. Please let me know if you need anything else.

Also, it would be great if you could answer the question in my previous reply:

Mahesh Gokhale said:

I would also like to know whether the data transmitted and received in SCI-compatible mode of LIN is in the FIFO format or LIFO format?

Regards,

Mahesh

Hi Vince,

This fixed my problem. Thanks a lot. There was a baud rate calculation error as you mentioned. I assumed the LIN module input clock to be 50MHz hence the fault. My code is now working.

Thank you and regards,

Mahesh