uart_configure() error -134 using UART_CFG_DATA_BITS_9

[Sean Montgomery]

I'm trying to use 9-bit UART communications with the nrf52840 using nRF Connect SDK v1.9.1, but I'm getting an error -134 when I call uart_configure().

When I use UART_CFG_DATA_BITS_8, uart_configure() and following UART polling work great, but UART_CFG_DATA_BITS_9 gives me a -134 error.

Here's my code:

//#define SAS_UART_DATA_BITS_8

#define SAS_BAUD_RATE 115200
#define SAS_PARITY UART_CFG_PARITY_NONE
#define SAS_STOP_BITS UART_CFG_STOP_BITS_1
#ifdef SAS_UART_DATA_BITS_8
    #define SAS_DATA_BITS UART_CFG_DATA_BITS_8
#else
    #define SAS_DATA_BITS UART_CFG_DATA_BITS_9
#endif
#define SAS_FLOW_CTRL UART_CFG_FLOW_CTRL_NONE

    struct uart_config cfg;
    cfg.baudrate = SAS_BAUD_RATE;
    cfg.parity = SAS_PARITY;
    cfg.stop_bits = SAS_STOP_BITS;
    cfg.data_bits = SAS_DATA_BITS;
    cfg.flow_ctrl = SAS_FLOW_CTRL;

    ctrl_uart = device_get_binding(DT_LABEL(DT_NODELABEL(uart1)));
    err = uart_configure(ctrl_uart, &cfg);

I've also tried adding CONFIG_UART_WIDE_DATA=y to prj.conf based on another forum post, but it didn't help.

Is there something else I need to do to use 9-bit UART data?

Thanks!

[Øivind]

Hi,

Only 8-bit UART data is supported for the zephyr driver for nrfx UART. I am not sure whether you can get 9-bit by using the nrfx API directly. I will have to get back to you about that after the Easter holidays.

[Sean Montgomery]

Thanks @Øivind that would be a huge help. I'm a bit stuck without any access to 9-bit and seemingly without any access to parity as well. I'm assuming that any attempt to bit-bang UART with softdevice running will be a nightmare, but any suggestions are welcome to get these UART features working.

[Øivind]

Hi again,

Unfortunately, it seems that only 8-bit data is supported, with the 9th data bit only being usable for parity.

I answered your question about parity support in your other ticket.