RE: UART low power shutdown issue

hmolesworth — Sat, 12 Oct 2019 18:37:32 GMT

Thanks! I merged the latest nrfx

RE: UART low power shutdown issue

Sigurd — Fri, 11 Oct 2019 12:07:32 GMT

Hi,

[quote userid="65515" url="~/f/nordic-q-a/53121/uart-low-power-shutdown-issue/214450"]Nordic might be able to say why not.[/quote]

New investigations shows that the real root cause for this issue is just a bug in the UARTE driver. The new driver version now waits for TX_STOPPED event before disabling the peripheral. This gracefully uinit of the UARTE peripheral was introduced in nrfx v1.7.2. See this link. (Note that SDK 15.3 is bundled with nrfx v1.6.2)

RE: UART low power shutdown issue

hmolesworth — Thu, 10 Oct 2019 15:27:58 GMT

You have identified the usual workaround; search for "0x40002FFC" or "0x40028FFC" to see multiple posts on this issue. It is covered implicitly by errata 89 for a different peripheral ([89] GPIOTE: Static 400 µA current while using GPIOTE), but there doesn't seem to have been a specific errata issued for the uart, which has even higher unwanted current; Nordic might be able to say why not.

I have these notes in my code though edit I see 2 versions:

  // Terminate UART transfers serial port - testing this to see if affects power consumption ToDo look into this again
  app_uart_close();
  // In app_uart_close() peripheral is disabled by writing 0 to the NRF_UARTE0->ENABLE
  // register. On 2840 this seems to not stop the HF clk and close the DMA bus, which could be a bug. Power
  // cycle the peripheral after calling app_uart_close() the current consumption goes down.
  *(volatile uint32_t *)0x40028FFC = 0;
  *(volatile uint32_t *)0x40028FFC;
  *(volatile uint32_t *)0x40028FFC = 1;
  or
  *(volatile uint32_t *)0x40002FFC = 0;
  *(volatile uint32_t *)0x40002FFC;
  *(volatile uint32_t *)0x40002FFC = 1;

Given the following I assume the first is correct (which we have used on Uart 0):

#define NRF_UARTE0_BASE             0x40002000UL
#define NRF_UART0_BASE              0x40002000UL
and
#define NRF_UARTE10_BASE            0x40020000UL

See this post: low-power-system-on-mode-in-ble_uart_app