BUG: APP_UART_FLOW_CONTROL_LOW_POWER sets all pins low

[David Robins]

Recently I was attempting to use the nrf51822 SDK's app_uart module's APP_UART_FLOW_CONTROL_LOW_POWER mode (currently using APP_UART_FLOW_CONTROL_ENABLED). I noticed that when I called app_uart_init all my LEDs came on. On investigation I noticed that in this block of code:

    // Configure hardware flow control.
    nrf_gpio_cfg_output(p_comm_params->rts_pin_no);
    NRF_GPIO->OUT = 1 << p_comm_params->rts_pin_no;

the OUT should be OUTSET, otherwise it sets all pins to 0 except RTS (and sets RTS high or disabled as intended). Perhaps this wasn't caught if the UART was initialized early and subsequent code configured other pins correctly before them being cleared was a problem? I am using SDK 6.0.0 but the issue is present in 6.1.0.

[Hung Bui]

Hi David and all,

I agree, it's clearly a bug. I have reported this internally to be fixed in the future version of the SDK.

Thanks for pointing out.