Zephyr nRF52840 device crashes when turning off UART with device_set_power_state(uart, DEVICE_PM_OFF_STATE, NULL, NULL)

RE: Zephyr nRF52840 device crashes when turning off UART with device_set_power_state(uart, DEVICE_PM_OFF_STATE, NULL, NULL)

Vid — Tue, 24 Nov 2020 12:08:56 GMT

We managed to disable UART at boot with the following code:

uart_irq_rx_disable(uart);

NRF_UARTE0->TASKS_STOPTX = 1;
NRF_UARTE0->EVENTS_RXTO = 0;
NRF_UARTE0->TASKS_STOPRX = 1;
while(NRF_UARTE0->EVENTS_RXTO == 0){}
NRF_UARTE0->EVENTS_RXTO = 0;
// disable whole UART 0 interface
NRF_UARTE0->ENABLE = 0;

NRF_UARTE0->PSEL.TXD = 0xFFFFFFFF;
NRF_UARTE0->PSEL.RXD = 0xFFFFFFFF;

we re-enable it when needed with:

uart_irq_rx_enable(uart)

The solution was proposed here

Regards,

Vid

RE: Zephyr nRF52840 device crashes when turning off UART with device_set_power_state(uart, DEVICE_PM_OFF_STATE, NULL, NULL)

Vid — Tue, 24 Nov 2020 10:38:03 GMT

Hi,

we couldn't disable uart0 completely, because we still use it to connect to device over BLE. So we want to be able to disable at boot, enable it when we need it and then disable it again.

In the meantime we have already found a solution, I'll post it below.

Regards,

Vid

RE: Zephyr nRF52840 device crashes when turning off UART with device_set_power_state(uart, DEVICE_PM_OFF_STATE, NULL, NULL)

Amanda Hsieh — Fri, 20 Nov 2020 13:46:38 GMT

Hi Vid,

Try to disable uart0 in the nrf52840dk_nrf52840.overlay to the project root folder which completely disables the UART0 peripheral:

&uart0 {
   status = "disabled";
};

You might have to clean/delete the build folder before recompiling.

-Amanda H.