nrf5340: Using the DTM sample firmware with SWDIO and SWDCLK as UART RX/TX

[kullum]

Hello,

We are looking at using the DTM sample firmware for BLE tuning in a form-factor version of our product. Unfortunately, the only GPIO pins we have exposed are SWDIO and SWDCLK. Is it possible to repurpose those as UART pins? If so, what do I need to change these pinctrl values to?

&pinctrl {
    uart0_default: uart0_default {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 30)>;
        };
    group2 {
      psels = <NRF_PSEL(UART_RX, 1, 11)>;
      bias-pull-up;
    };
    };

    uart0_sleep: uart0_sleep {
        group1 {
            psels = <NRF_PSEL(UART_TX, 0, 30)>,
                <NRF_PSEL(UART_RX, 1, 11)>;
            low-power-enable;
        };
    };
};

[mathiaso]

Hi, Alexander.

As can be seen in the UARTE PSEL.TXD and PSEL.RXD register descriptions, the UART_TX and UART_RX signals have to be routed to GPIO ports [0..1], and pins [0..31]. The pin assignments list shows that SWDIO and SWDCLK only have debug functionality. Hence, the SWD pins can not be used as UART pins.

Best regards,
Mathias