Can't change UART parity

[Steve Rathjen]

How to change the parity bit on UART on NRF54L15?

prj.conf includes:

CONFIG_SERIAL=y
CONFIG_UART_20_NRF_PARITY_BIT=y

DT overlay includes:

&uart20 {
    parity = "even";
};

Also tried:

const struct uart_config uart_cfg = {
    .baudrate = 115200,
    .parity = UART_CFG_PARITY_EVEN,
    .stop_bits = UART_CFG_STOP_BITS_1,
    .data_bits = UART_CFG_DATA_BITS_8,
    .flow_ctrl = UART_CFG_FLOW_CTRL_NONE
};

Then..
    while(!device_is_ready(uart_dev));

    int err = uart_configure(uart_dev, &uart_cfg);
    while(err == -ENOSYS);

..but err = -134 (-ENOSUP?)

Using Polling:

    //Test 1
    //Check for UART traffic
    unsigned char uartRxBuff[20];
    uartRxBuff[0] = 0;
    int n = uart_poll_in(uart_dev, &uartRxBuff[0]);
    if(uartRxBuff[0] != 0)
    //if(uartRxBuff[0] == 0x79)
    {
        uartRxBuff[0] = 0x9f;
        uart_poll_out(uart_dev, uartRxBuff[0]);
    }

With Even parity on the other UART device it receives: 0x1f, if I send 0x1f in above code the other device receives 0x9f!  Same deal with data received by NRF54L15 - the MSBit is flipped.  If I switch the other device to parity=NONE (test FW - the actual FW is fixed at EVEN parity) the data comes thru correctly.

I was also unable to change the default UART20 RX/TX pins with the overlay - maybe it's the same problem??  It seems the overlay is ignored regarding UART20.

Is changing parity supported?  Is there some conflict with TF-M or logging?  How to change parity?  The 'other' device uses EVEN parity and it cannot be changed. 

Thanks!

[Henri]

Hey, I found the issue. The nrfx driver does not support 7 data bits, even though the hardware does. I fixed this by changing:

if (cfg->data_bits != UART_CFG_DATA_BITS_8) {

        return -ENOTSUP;

}

to 

#if NRF_UARTE_HAS_FRAME_SIZE

    switch (cfg->data_bits) {

    case UART_CFG_DATA_BITS_7:

        uarte_cfg.frame_size = NRF_UARTE_FRAME_SIZE_7_BIT;

        break;

    case UART_CFG_DATA_BITS_8:

        uarte_cfg.frame_size = NRF_UARTE_FRAME_SIZE_8_BIT;

        break;

    default:

        return -ENOTSUP;

    }

#else

    if (cfg->data_bits != UART_CFG_DATA_BITS_8) {

        return -ENOTSUP;

    }

#endif

in uart_nrfx_uarte.c. Added to that I removed the line setting uarte_cfg.frame_size to 8.