UART SDK12 NRF_LOG_GETCHAR() does not work

[vit bernatik]

When I use NRF_LOG_GETCHAR() witn nRF52 DK and onboard SEGGER UART it stops in next NRF_LOG_INFO(). Also after ARM reset it keeps in this error state. It seems that SEGGER does not correctly drive CTS pin.

Also it is strange that when I disable UART flow control setting:

#define NRF_LOG_BACKEND_SERIAL_UART_FLOW_CONTROL 0

Then NRF_LOG_GETCHAR() does not work. But at least NRF_LOG_INFO() works after ARM reset.

[vit bernatik]

I found a fix - you need to change a file: SDK12\components\drivers_nrf\uart\nrf_drv_uart.c lines 81 and 94 from:

nrf_gpio_cfg_input(p_config->pselcts, NRF_GPIO_PIN_NOPULL);

Into:

nrf_gpio_cfg_input(p_config->pselcts, NRF_GPIO_PIN_PULLDOWN);

Also note that flow control has to be enabled in "sdk_config.h":

#define NRF_LOG_BACKEND_SERIAL_UART_FLOW_CONTROL 1

Note that another option is to add external pull down on CTS (P0.7) and it starts work. Even when I touch it by finger it works...

[639zw]

Thanks for this answer saved me a bit of time. Just as an update for others: NRF_LOG_GETCHAR() does now work without hardware flow control. (Tested with NRF52-DK SDK 12.2.0)