Investigate supporting power management in arduino-esp32 (DFS + tickless idle)

[igrr]

Related area

Power management

Hardware specification

All ESP32 series chips

Is your feature request related to a problem?

Recently a community member has mentioned that the current consumption of ESP32 connected to Wi-Fi is too high. While it is possible to reduce current consumption with ESP-IDF, this option is not accessible to Arduino users.

Describe the solution you'd like

To reduce current consumption in Wi-Fi connected state, several things are required:

• Power management should be enabled (CONFIG_PM_ENABLE).
  • Investigate what are the downsides enabling it if it is not turned on at run time.
• FreeRTOS tickless idle should be enabled (CONFIG_FREERTOS_USE_TICKLESS_IDLE).
  • Investigate what are the downsides enabling it if the DFS and automatic light sleep are not enabled at runtime.
• Enabling DFS and automatic light sleep at run time via some API.
• An easy-to-understand example showing how to achieve lower current consumption when Wi-Fi is connected.
• Documentation explaining the caveats (mostly related to peripherals and timers) of enabling the above mentioned features.

Describe alternatives you've considered

Keep not supporting DFS and tickless idle in Arduino. But then everyone keeps thinking that it's not possible to have Wi-Fi connection with lower average current.

Additional context

No response

I have checked existing list of Feature requests and the Contribution Guide

• I confirm I have checked existing list of Feature requests and Contribution Guide.

[our30K]

just want to pump this up , is there anyone working on this ? it has been a long while :)

[tshcherban]

i can take a look at this. recently i've been playing around with IDF and power management API, can try applying this to the arduino core.
@igrr @our30K can i sometimes ping you here if any questions?

[our30K]

that would be great, I am interested in both low power WIFI and BLE via arudino.

[tshcherban]

I've added arduino core and some of the arduino libs (OneWire, DallasTemperature) as a components to ESP-IDF.
Currently enabled CONFIG_PM_ENABLE, CONFIG_FREERTOS_USE_TICKLESS_IDLE and used automatic light-sleep with esp_wifi_set_ps(wifi_ps_type_t::WIFI_PS_MAX_MODEM) and esp_pm_configure.
Used a simple HttpClient request and OneWire library to test if it's alive. millis works as expected since it relies on esp_timer_get_time.
Will try using those APIs at runtime, enabling/disabling power-saving on demand. And i have nordic power profiler 2 kit, so can investigate how much gain from DFS vs static frequency.
Do you have any good ideas of what stuff can be broken most probably? so i can add those to my 'test sketch'
P.S. preliminary results on enabling DFS (no significant improvement in powersaving)

160 MHz, ~33 mA

10..160 MHz, ~33 mA

80..160 MHz, ~34 mA

On 10..160 MHz range started to observe Serial.print problems, especially on large amounts of text (I'm using it to print the results of a vTaskList function):

Serial log

Time since bootup: 17369385 us
Lock stats:
Name            Type            Arg    Active    Total_count    Time(us)  Time(%)
wifi            APB_FREQ_MAX    0      0         63             2268808   14 %
rtos1           CPU_FREQ_MAX    0      1         2955           4704990   28 %
rtos0           CPU_FREQ_MAX    0      1         2330           1252689   8  %

Mode stats:
Mode      CPU_freq    Time(us)    Time(%)
SLEEP     10 M        12339504    70%
APB_MIN   10 M        0           0 %
APB_MAX   80 M        1451702     8 %
CPU_MAX   160M        3167449     18%

Sleep stats:
light_sleep_counts:68  light_sleep_reject_counts:0
Task Name       Status  Prio    HWM     Task    Affinity
main            X       1       2164    4
IDLE            R       0       556     6
IDLE            R       0       544     5
tiT             B       18      1896    8
ipc0            S       24      520     1
Tmr Svc         B       1       1320    7
ipc1            S       24      484     ����e��������������er          S       22      3088    3
wifi            B       23      3752    11
arduino_events  B       �����J10
sys_evt         B       20      588     9

[tshcherban]

Also compared existing API from WiFiGenericClass::setSleep (withoud IDF menuconfig modifications), value WIFI_PS_MIN_MODEM is used by default (not for ESP32-S2 though)

[TD-er]

On 10..160 MHz range started to observe Serial.print problems, especially on large amounts of text (I'm using it to print the results of a vTaskList function):

Which is totally expected as below 80 MHz the clock source is likely to change from PLL_CLK to XTAL_CLK or RC_FAST_CLK.
I'm not sure all timings related to APB clock are updated when switching clock source or going below 80 MHz CPU frequency.
Well... I'm quite sure there are things getting out of sync between Arduino and ESP-IDF when you change it, but not sure what effect this will have.
Both ESP-IDF and Arduino tend to keep their own administration on this matter and I know there are parts of the code where both are not notifying each other (or rather listening to notifications).

N.B. It might be possible this "80 MHz" threshold differs among ESP32-variants as the ESP32-C2 for example does have a clock based on multiples of 60 MHz.

I can imagine the issues you saw with serial also depend on the used baud rate as not every baud rate can be perfectly matched with an integer factor from each clock frequency.
So some ratios may lead to a bigger "error" in matching clock frequencies.