my nrf52833 uart tx pin is low level when it is idle.

[nick yong]

I find my uart tx pin is low level when it is idle . it is abnormal. 

how to change code to make it normal: hight level in idle.

thanks. 

[Einar Thorsrud]

Hi,

I am not immediately able to explain that. Can you share/show how you have configurd and use the UART, both in code/configuration and hardware?

[nick yong]

    NRF_UART0->PSEL.RXD = pinrx;

    NRF_UART0->PSEL.TXD = pintx;

    NRF_UART0->BAUDRATE = DEF_uart_baud; // value for 115200

&pinctrl {

    uart0_default: uart0_default {

        group1 {

            psels = <NRF_PSEL(UART_TX, 1, 1)>,  

                    <NRF_PSEL(UART_RX, 0, 4)>;

        };

       

    };

    uart0_sleep: uart0_sleep {

        group1 {

            psels = <NRF_PSEL(UART_TX, 1, 1)>, 

                    <NRF_PSEL(UART_RX, 0, 4)>;

        };

       

    };

is there some register to inverse the uart pin logic?  up to now, I cannot find the configuration about polarity。

the uart register would contol all the behavior?  which register would control the logic level. thanks. 

[Einar Thorsrud]

Hi,

The nRF UARTE periphearl does not support inverse polarity, so this is not it. Does the other device have pull-up enabled on the Rx pin? If so, perhaps it woud make sense to enable pull-up on the Tx pin (though unconventional). That is also what we do on our development kits by default, see here.