Low Power Modes

[CyberCityCircuits]

Do you have any plans on implementing the native low power modes that the RP2040?  This would be deeply appreciated.

[earlephilhower]

In the short term I'm unfortunately occupied with other things, but to access the pico-extra sleep functions should be possible with some simple modifications to the core. (This is also for #344)

Basically, you will need to rebuild libpico.a to include the pico_sleep directory and add the proper include path to platform_inc to let the IDE fine the proper headers.

1. Add the pico_sleep line to the Cmakefile.txt: https://github.com/earlephilhower/arduino-pico/blob/master/tools/libpico/CMakeLists.txt
2. Rebuild libpico.a by running make-libpico.sh https://github.com/earlephilhower/arduino-pico/blob/master/tools/libpico/make-libpico.sh
3. Add the pico-extras/pico_sleep path to pl;atform_inc.txt: https://github.com/earlephilhower/arduino-pico/blob/master/lib/platform_inc.txt (the format is a little off but should be obvious)

Restarting the IDE should then give the ability to #include <pico/sleep.h> and call the functions exported there. Note that I have not looked deeply at this and it is in the extras repo so it may not be 100% working from the RPi folks,yet. I have a feeling you'll need to do things like save/restore all active clocks, set which clocks to disable in sleep mode, and make sure I/Os are set to appropriate drive strengths/inputs.

[WildkatzGithub]

Hello, I tried to run make-libpico.sh with GitBash, but don't work.
I want to access pico sleep functions, too.

$ ./make-libpico.sh
./make-libpico.sh: line 6: cd: ../../system/arm-none-eabi/bin: No such file or directory
./make-libpico.sh: line 11: cmake: command not found

[earlephilhower]

You'll need to clone the git repo, run the get.py script to fetch the toolchain (your 1st missing exe), and also of course have cmake installed(the 2nd one). It uses the pico-sdk build process, so all the pico-sdk prerequisites are needed.

For cmake, your distro's package manager should have it (apt install cmake or yum install cmake as the case may be...)

[WildkatzGithub]

Thx for help! I have cloned the git repo, ran get.py and installed cmake.
& cmake was found by GitBash, but now it hangs around line 12:

./make-libpico.sh: line 12: make: command not found

I can't install the apt or yum package manager as I'm currently using only Windows 10.

Would it be better to use Linux for this?

[earlephilhower]

Would it be better to use Linux for this?

Short answer is, "Yes." Long answer is, "Yeeeeeees." :) WSL will work fine too.

Alternatively, you can see how they build the Pico SDK under Windows. There is a readme in their project, but I never looked at it since I didn't have the need. The build prerequisites they need are what the makelibpico.sh script requires, too.

[WildkatzGithub]

Thank you for showing me these possibilities :)
At https://github.com/raspberrypi/pico-playground I read that the use of pico_sleep is not yet stable.

I took current measurements on the Pico yesterday.
The Pico needs 15 mA in a simple while loop at 125 MHz and only one core. Without external components and peripherals, of course.
If I now set the system clock to 10 MHz, it only needs 1 to 2 mA in the same loop. That is sufficient for my application.

With this I avoid the use of pico_sleep and the known problems like "frozen pico" or "printf () / puts () - not possible" after sleep / dormant.

[alfonsoletizia1]

@WildkatzGithub how did you succeded in setting the clock to 10 MHz? I tried using platform io, but then it's unusable

[WildkatzGithub]

Hello, you can set the clock to 10 MHz with this code in the Arduino IDE:

#include "pico/stdlib.h"

set_sys_clock_khz(10000, true); // Set System clock to 10000 kHz

I've already tried lower clocks, but 10 MHz was the lowest clock speed so far without the Pico getting stuck.
Please let me know if you can find a lower clock.

By the way, if the clock is currently set to 10 MHz, the Pico can only be programmed using the button at this point.

[sail81]

@WildkatzGithub thank you so much for your 10 MHz power saving hint. A great idea indeed. In my application I do some outdoor measurement every minute and send it via LoRa. In between I have 59s delay. The pico is driven by 3 rechargeable AA NiMH batteries. After I saw your post I created this function:

void power_save(uint16_t psinterval){
LoRa.sleep();
delay(2);
set_sys_clock_khz(10000, false); // Set System clock to 10 MHz, sys_clock_khz(10000, true); did not work for me
delay(2);
vreg_set_voltage(VREG_VOLTAGE_0_95); // 0.85V did not work, 0.95V seems pretty stable
delay(psinterval);
vreg_set_voltage(VREG_VOLTAGE_DEFAULT); // corresponds to 1.10V, not sure if that is really required for 48 MHz
delay(2);
set_sys_clock_48mhz(); // Set System clock back to 48 MHz to make LoRa work
delay(2);
LoRa.idle();
}

Now I am testing it since 3 days and it runs stably. I can already tell that the battery voltage drops much slower that before. I should have measured the power consumption before. I will do that once my test is completed. One could play with the voltages, too. Though, I have not yet an idea how much power saving would benefit from that. Let's see.

When checking lower clocks than 10 Mhz did you run more that a delay()?

[earlephilhower]

Looks like this is closed. Unfortunately the Pico SDK sleep modes are unstable per above, but setting a low system clock seems to help at the cost of peripheral(USB) issues.

[JudgeBeeb]

Has anyone managed to get sleep_pico working in the Arduino IDE yet? whenever I try to build libpico.a I get the following errors:
ar: stdio.c.obj: not found in archive ar: stdio_usb.c.obj: not found in archive ar: stdio_usb_descriptors.c.obj: not found in archive

[DansDesigns]

Hello, you can set the clock to 10 MHz with this code in the Arduino IDE:

#include "pico/stdlib.h"

set_sys_clock_khz(10000, true); // Set System clock to 10000 kHz

I've already tried lower clocks, but 10 MHz was the lowest clock speed so far without the Pico getting stuck. Please let me know if you can find a lower clock.

By the way, if the clock is currently set to 10 MHz, the Pico can only be programmed using the button at this point.

sorry for reviving an old threat but I am wondering if the Pico/rp2040 would stay in the 10Mhz setting after a power cycling or would it revert to the original set frequency in the sketch settings upon reboot?

[earlephilhower]

On reboot the rom and app will set the core to 133mhz until your app changes it again. So you could set the frequency in your setup() if desired and only a short period would be at the higher frequency.

[NuclearPhoenixx]

Looks like this is closed. Unfortunately the Pico SDK sleep modes are unstable per above, but setting a low system clock seems to help at the cost of peripheral(USB) issues.

Is this still the case today? Are there any alternatives to using the native Pico SDK sleep functions that you know of?
Like for example the Adafruit SleepyDog lib: https://github.com/adafruit/Adafruit_SleepyDog