TIDC-CC2650STK-SENSORTAG: Change uart baudrate on the fly

Egor Karlin

Part Number: TIDC-CC2650STK-SENSORTAG

Hi, I need some help with UART.

I need to change the UART Baud Rate dynamically.

At the beginning UART Baud Rate is 300. UART in CallBack mode. After the message is received, my program should respond by sending ybuf array with Baud Rate 300.
After that I close UART, change its baudRate to 9600 and open UART again.
Than my program should respond by sending zbuf array with Baud Rate 9600. Then, whenever a new message arrives, the arrays are sent with Baud Rate 9600.

It works only one time. Function readCallback is no longer called.

The source code of my program is presented below:

static void readCallback(UART_Handle handle, void *rxBuf, size_t size)
 {
    Event_post(eventH, UART_RX_COMPLETE);
 }

void taskFxn(UArg arg0, UArg arg1)
{
    eventH = Event_create(NULL, NULL);

    UART_Handle Uhandle;
    UART_Params Uparams;

    UART_Params_init(&Uparams);
    Uparams.writeDataMode = UART_DATA_BINARY;
    Uparams.readDataMode  = UART_DATA_BINARY;
    Uparams.readMode      = UART_MODE_CALLBACK;
    Uparams.readCallback  = &readCallback;
    Uparams.baudRate      = 300;

    Uhandle = UART_open(Board_UART, &Uparams);
    wantedRxBytes = MBUS_FRAME_DATA_LENGTH;
    UART_control(Uhandle, UARTCC26XX_CMD_RETURN_PARTIAL_ENABLE, NULL);
    UART_read(Uhandle, rxBuf, wantedRxBytes);

    while(true)
    {
        uint16_t events = Event_pend(eventH, Event_Id_NONE, 0xFFFFFFFF, BIOS_WAIT_FOREVER);

        if (events & UART_RX_COMPLETE)
        {
            uint8_t ybuf[3] = {0x1, 0x2, 0x3};
            uint8_t zbuf[3] = {0x4, 0x5, 0x6};

            UART_write(Uhandle, ybuf, 3);
            UART_close (Uhandle);

            Uparams.baudRate=9600;
            Uhandle = UART_open(Board_UART, &Uparams);
            UART_write(Uhandle, zbuf, 3);

            Task_sleep(10000);
            Event_post(eventH, UART_TX_COMPLETE);
        }

        if (events & UART_TX_COMPLETE)
        {
            UART_read(Uhandle, rxBuf, wantedRxBytes);
        }

    }
}

Where could my mistake be?
Regards, Egor.

over 4 years ago

0 YiKai Chen over 4 years ago

Guru 735455 points

Do you set breakpoint to check what Uhandle do you get after you call UART_open?

0 Egor Karlin over 4 years ago in reply to YiKai Chen

Intellectual 690 points

Hi, YiKai Chen, thanks for the quick response.

Yes, the first time I checked the Uhandle after executing the calling UART_open when I set BaudRate 300, the second time I checked the Uhandle when I opened the UART with new parameters. All parameters of the Uhandles matched except BaudRate.

This screenshot shows the Uhandle parameters for BaudRate 300:

This screenshot shows the Uhandle parameters for BaudRate 9600, after I set it in while loop:

0 Egor Karlin over 4 years ago in reply to YiKai Chen

Intellectual 690 points

I noticed that after changing the baudrate, the read callback function works if I send a message at the old BaudRate, but the parcel size is not transmitted to the callback function. If I send a parcel with a new BaudRate, the call back does not work at all.

How do I change UART BaudRate dynamically?

0 Egor Karlin over 4 years ago

Intellectual 690 points

Part Number: TIDC-CC2650STK-SENSORTAG

Hi All,

Is it possible to change UART BaudRate dynamically if UART in Callback mode?

0 Eirik V over 4 years ago in reply to Egor Karlin

TI__Guru 56590 points

TI-RTOS drivers currently do not support dynamically changing the baud rate while the driver is open. To safely change the baud rate, you should close the instance & reopen it with the new baud rate. This will ensure all driver internals & registers are configured correctly.

0 YiKai Chen over 4 years ago in reply to Egor Karlin

Guru 735455 points

I write a simple test program which combine pininterrupt and uartecho examples to do barudrate switch dynamically and it works as expected. You have to make sure you call UART_close before you call UART_open to set new baudrate.

0 Egor Karlin over 4 years ago in reply to YiKai Chen

Intellectual 690 points

Thank you very much for the example provided. I added a baudrate_change flag and a while loop into my project for checking this flag. Now my program works as it should.

0 Eirik V over 4 years ago in reply to YiKai Chen

TI__Guru 56590 points

Thanks for the pin interrupt idea YiKai Chen! Nice :).

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TIDC-CC2650STK-SENSORTAG: Change uart baudrate on the fly