ULP running in background

[cruzxia]

I am working on a project that needs to run in low power battery backup mode if the mains fails.
I have to increment some timing variables with a 1ms base, and they need to run uninterrupted non stop.
I am using an external 32768 crystal to run the RTC.
Currently I am using an interrupt timer on the main processor to run the timing, I was hoping to migrate it into the ULP.

My questions are:

1. If I setup the ULP to increment the timing variables, can I leave it running in an endless timing loop whilst the main processor is operating?
2. Can I read the timing variables in the main processor while the ULP is running?
3. How do I access the ULP variables from the main processor?
4. What is the processor speed of the ULP?

If the power fails I was planning to enable ULP wake up and enter deep sleep.
The main processor could then be woken via button push or ADC voltage level (power restored) in the ULP.

[ESP_krzychb]

Hi cruzxia,

1. If I setup the ULP to increment the timing variables, can I leave it running in an endless timing loop whilst the main processor is operating?

Yes

2. Can I read the timing variables in the main processor while the ULP is running?

Yes

3. How do I access the ULP variables from the main processor?

See https://github.com/espressif/esp-idf/tr ... system/ulp

4. What is the processor speed of the ULP?

ULP uses RTC_FAST_CLK, which is 8 MHz