This is a simple demo to show how you can place the pico into a low power dormant mode, which according to the docs will pull around 0.8mA and then wake it using an external DS3231. This should be useful to allow minimal power consumption and periodic waking to perform some work.
This is based off the code provided here
Layout as follows:
~/pico/pico-sdk/
~/pico/pico-extras/
~/pico/picosleeprtc/
Create a new build dir inside this repo:
mkdir ~/pico/picosleeprtc/build
Change into the directory and run the following:
export PICO_SDK_PATH=../../pico-sdk
export PICO_EXTRAS_PATH=../../pico-extras
cmake ..
make
This will create the sleep.elf file below. Alternatively drag the sleep.uf2 file onto the pico via usb.
To deploy this using SWD and monitor using minicom, run the following once you have wired everything up as per the pico docs.
Start following in a terminal:
openocd -f interface/raspberrypi-swd.cfg -f target/rp2040.cfg
Also start minicom to listen for output in a new terminal:
minicom -b 115200 -o -D /dev/serial0
Enter gdb and load file:
gdb-multiarch sleep.elf
target remote localhost:3333
load
monitor reset init
continue
In the minicom terminal window you should see debug output and the led should blink on and off each minute.
For more details, such as wiring instructions please see this post.