CC2652P: whether uart need close or not when CC2652P cpu enter sleep for lowest power consumption?

yingtao jia

Expert 1280 points

Part Number: CC2652P

Hi, I use CC2652P on my target, SimpLink SDK v4.20,.

When I test sleep current on my target, I found this:

If I close uart with UART_close(UartHandle) in TI Drivers, then sleep current on my target is 14uA.

If I didn't close uart, then sleep current on my target is 1.7mA.

And I initialized spi, i2c, adc in my code. Spi, i2c, adc remains open in init procedure, and they have no influence to sleep current.

In a word :

SPI, I2C, ADC open, UART open: 1.7mA

SPI, I2C, ADC open, UART close: 14uA.

So, is closing uart a necessary step for low power application?

over 5 years ago

0 IUsedToBeARealPerson (M-W) over 5 years ago

TI__Guru 58425 points

Hi Yingtao,

You do not need to close it to go into full standby. You do however need to make sure that it is in idle, meaning that there is no read/write operation being left active.

You could try to for example call UAR_readCancel() before going into standby to see if you might be having an active read.

0 yingtao jia over 5 years ago in reply to IUsedToBeARealPerson (M-W)

Expert 1280 points

Thank you, I use UART_readCancel() before going into standby, and it still remains 1.7mA.

UART_close can be 14uA.

0 IUsedToBeARealPerson (M-W) over 5 years ago in reply to yingtao jia

TI__Guru 58425 points

Hi Yingtao,

Could you share the code that relates to UART in your application so that I could better understand what you are doing and what could be the issue?

0 yingtao jia over 5 years ago in reply to IUsedToBeARealPerson (M-W)

Expert 1280 points

This is app_uart_init():

void app_uart_init(void)
{
    UART_init();

    UART_Params_init(&uartParams);

    uartParams.baudRate         = 460800;

    uartParams.writeMode        = UART_MODE_BLOCKING;
    uartParams.writeDataMode    = UART_DATA_BINARY;
    uartParams.writeTimeout     = 1000;

    uartParams.readMode         = UART_MODE_CALLBACK;
    uartParams.readDataMode     = UART_DATA_BINARY;
    uartParams.readReturnMode   = UART_RETURN_FULL;
    uartParams.readEcho         = UART_ECHO_OFF;
    uartParams.readCallback     = UartReadCallback;


    UartHandle = UART_open(UART_Debug, &uartParams);

    // rx pull up
    IOCIOPortPullSet(IOID_12, IOC_IOPULL_UP);

    if (UartHandle == NULL) {
        /* UART_open() failed */
        while (1);
    }

    UART_control(UartHandle, UARTCC26XX_CMD_RETURN_PARTIAL_ENABLE, NULL);
    UART_read(UartHandle, uartrx_buf, sizeof(uartrx_buf));
}

This is app_uart_close():

void app_uart_close(void)
{
    UART_close(UartHandle);
}

This is entering standby code in a app TI-RTOS task:

app_uart_close();

while (1)
{
	Semaphore_pend(gSem, BIOS_WAIT_FOREVER);
}

The phenomenon is:

If I use code above , the current is 14uA;

If I comment app_uart_close() so that uart stays open, the current goes to 1.7mA.

0 IUsedToBeARealPerson (M-W) over 5 years ago in reply to yingtao jia

TI__Guru 58425 points

Hi,

Based on the code above, that would be the expected behavior yes. Without the "close", your initial UART_read() would remain active and keep you out of standby. If you said that using "readCancel" did not work, consider if you might be restarting the read again inside the callback?

0 yingtao jia over 5 years ago in reply to IUsedToBeARealPerson (M-W)

Expert 1280 points

Thank you.

Use uart_cancel() in readcallback works.

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CC2652P: whether uart need close or not when CC2652P cpu enter sleep for lowest power consumption?