Why is RTC timer lost during deep sleep?

[tve]

Is it a design feature that the RTC timer is lost during deep sleep? I observe the following (using SDK 1.3):

The chip is awakened from deep sleep after a timer expiration using a gpio16->ext_rst connection

The RTC memory (system_rtc_mem_read/write) is preserved during deep sleep

The RTC clock must be running during deep sleep since it awakens the chip

When the chip awaken, the RTC clock (system_get_rtc_time) is reset to 0

Why?

[tve]

By the way, is it expected that after a deep sleep system_get_rst_info->reason == REASON_EXT_SYS_RST and not REASON_DEEP_SLEEP_AWAKE ?

[dkinzer]

is it expected that after a deep sleep system_get_rst_info->reason == REASON_EXT_SYS_RST and not REASON_DEEP_SLEEP_AWAKE ?

That is a bug in v1.3.0 (and probably earlier) of the SDK. It was fixed in a special build of v1.3.0 but I haven't checked to see if the correction made it into v1.4.0.

[tve]

Thanks for the note about the reset reason, it is fixed in 1.4!

The fact that the RTC clock is reset is still a puzzle.

[torntrousers]

I'm interested in this question too -

When the chip awaken, the RTC clock (system_get_rtc_time) is reset to 0

It would be really useful if there was a way to prevent that happening.

[ESP_Faye]

Hi,

Sorry for the inconvenience.

ESP8266 designed like this, wake up from deep-sleep, the RTC timer will be reset, but the data stored in RTC memory will not.

You could call system_get_rtc_time before deep-sleep and write the value into RTC memory by system_rtc_mem_write.

[eriksl]

Interesting though, because the RTC is supposed to keep running in deep sleep, because it needs to be able to wakeup the rest of the chip...

[Dmytro]

Reset RTC to 0 is real problem for me, I use deep-sleep, and during sleep time interrupt from external sensor may occur. External sensor connected to RESET line of ESP8266 and must wake up module, but after wake-up I can't calculate time was sleeping (and time left). Can you give some mechanism for direct RTC control? I didn't found detailed description of RTC module (registers, control bits and so on).

[eriksl]

Add external RTC, their very cheap (using I2C for example).

[SpenZerX]

Will RTC timer keep running in deep sleep when connecting PIN VDD_RTC?