Add pico_low_power library by will-v-pi · Pull Request #2852 · raspberrypi/pico-sdk

will-v-pi · 2026-03-06T18:05:49Z

This adds a pico_low_power library, which allows going to sleep, dormant, and powman pstates.

Also adds bitsets and hardware_rosc, to support the low power stuff.

Includes a possible fix for #2420 to get the bazel rp2040 clang build working

Also requires raspberrypi/picotool#298 when putting persistent data in XIP SRAM

See low_power.h for documentation

Allows for much simpler custom linker scripts

…ript_var variables Means that CMake doesn't need to know the default memory addresses for different platforms

…l files easier Restructured so that it includes the platform-specific files before common ones, so common ones can be overridden

Use new include_linker_script_dir and use_linker_script_file functions to add the linker arguments

Breaking change for Bazel builds using different binary types, instead of setting PICO_DEFAULT_LINKER_SCRIPT to eg `//src/rp2_common/pico_crt0:no_flash_linker_script` it is now `//src/rp2_common/pico_standard_link:no_flash_linker_script`

Treat rp2040 layout (boot2 instead of embedded blocks) as the outlier

…cripts

lurch · 2026-03-06T18:12:40Z

+
+static inline generic_bitset_t *bitset_write_word(generic_bitset_t *bitset, uint word_num, uint32_t value) {
+    check_bitset(bitset);
+    if (word_num < bitset_word_size(bitset)) {


Should this raise an error if word_num >= bitset_word_size(bitset) ?

This is a question for @kilograham, but given that the other functions don't throw any errors when you attempt to pass a value that is outside the range and just return 0/do nothing, I think this one should also not throw an error?

Add low_power_xx_for_ms functions, which handle starting AON timer if necessary Add low_power_set_external_clock_source function to avoid the need to have src_hz and gpio_pin in the arguments passed to low_power_dormant_until_aon_timer, and for RP2040 you just need to call low_power_set_external_clock_source beforehand (no-op on RP2350) Add DORMANT_CLOCK_SOURCE_DEFAULT and DORMANT_CLOCK_HZ_DEFAULT, so you don't need `#if PICO_RP2040` in user code

will-v-pi · 2026-04-22T17:11:43Z

Latest commit changes the signature for low_power_dormant_until_aon_timer to remove the src_hz and gpio_pin arguments. Those must now be passed to a separate function low_power_set_external_clock_source, which is ignored on non-RP2040 platforms, and for RP2040 it stores the values for use in low_power_dormant_until_aon_timer later.

I think this is cleaner than having unused src_hz and gpio_pin in the low_power_dormant_until_aon_timer signature, when those parameters are only used on RP2040.

Also adds low_power_xx_for_ms functions to just go to low power mode for a duration - these setup the AON timer for you, if it's not running already

peterharperuk · 2026-04-23T09:16:29Z

Are you happy this is correct now? I can retest if you are.

Also increase powman_set_power_state timeout when waiting for POWMAN_STATE_WAITING_BITS, as it was sometimes timing out

This writes the calibrated frequency for the LPOSC to improve the accuracy, and switches it back to the default XOSC when waking up

It is unreliable, see RP2040-E10

will-v-pi · 2026-04-23T10:35:59Z

Are you happy this is correct now? I can retest if you are.

Yes, I think I'm happy it's ready for retesting now

peterharperuk

Seems good now. Some examples here if anyone wants them https://github.com/peterharperuk/pico-examples/tree/low_power_examples

Also use low_power_start_aon_timer_at_time_ms in low power tests

…placed between bss and heap Default section_persistent_data.incl now goes into RAM, and you need to override the file to put it at a specific address, to ensure HEAP_LOC is always set correctly in that case

Use external_sleep_timer to check sleeps are actually 2s, and use that instead of rtc_clksrc

The aon_timer test had an infinite while loop

Passes --no-clear arg when not clearing, rather than --clear when clearing, as older picotool doesn't have a --clear flag This will break the build of low_power_test_timers_encrypted unless you use the xip-sram branch of picotool

will-v-pi added 15 commits March 6, 2026 15:29

Separate linker scripts out into include files

b8f699f

Allows for much simpler custom linker scripts

Add customisable heap location, with pico_set_linker_script_var function

6dc06e6

Add kitchen sink test of custom linker scripts

727cabd

Separate out rp2_common and platform-specific linker script sections

3a83dc7

More de-duplication

4b1a3ec

Make overriding ram locations simpler

ae97a22

Make it possible to reference default locations in pico_set_linker_sc…

3811e67

…ript_var variables Means that CMake doesn't need to know the default memory addresses for different platforms

Add pico_add_linker_script_override_path to make overriding individua…

a20f86a

…l files easier Restructured so that it includes the platform-specific files before common ones, so common ones can be overridden

Add simple overlay demo

6bd9e5b

Add scripts to bazel build

2bf8555

Use new include_linker_script_dir and use_linker_script_file functions to add the linker arguments

Move linker scripts out of crt0

fe2d56b

Breaking change for Bazel builds using different binary types, instead of setting PICO_DEFAULT_LINKER_SCRIPT to eg `//src/rp2_common/pico_crt0:no_flash_linker_script` it is now `//src/rp2_common/pico_standard_link:no_flash_linker_script`

Make rp2350 text sections the default

1bd7089

Treat rp2040 layout (boot2 instead of embedded blocks) as the outlier

Rename scripts include directories to standard_scripts and platform_s…

72adb67

…cripts

Move and add example to Bazel docs for changing linker scripts

e47fe09

Add cc_library load to new bazel files

9c0ed0c