SleepyPico

What it is

Weather Station Example for using sleep and dormant mode of Raspberry Pi Pico and SSD1306, BME280.

The source code comprises:

the Raspberry Pi Pico application SleepyPico that uses the Pico's sleep and dormant modes.
the library class Sleep that is responsible for the sleep functionality and provides an Arduino-like event loop.
an OLED driver for the SSD1306 display (by Larry Bank).
a driver for the BME280 sensor (Bosch) that measures humidity, temperature, pressure.

Notice about authors

The OLED-Library was developed by Larry Bank.
The BME280 SPI driver in C was developed the Raspberry Pi Foundation.
The BME280 SPI driver in C++ was created by Michael Stal.
The Sleep class was created by Michael Stal.
The main application SleepyPico was developed by Michael Stal.

Thanks

to GitHub user Rene for his very helpful suggestions how to improve the code.

Some remarks on the code

The mode is determined by the configure() methods provided by the Sleep class (Sleep.cpp, Sleep.hpp)

SLEEP => Pico wakes up upon RTC timer alarm. Sleep time can be dynamically changed.
DORMANT => Pico wakes up when signal is detected on the wakeup_pin. Boolean argument edge defines whether a leading edge (true) or trailing edge (false) wakes up the Pico. Boolean argument active defines whether GPIO pin is active high (true) or active low (false).
NORMAL => Pico does not use one of the sleep modes.

In either mode the system frequency is reduced to 60 MHz to reduce consumption. The BME280 is executed in forced mode to increase power savings. The OLED SSD1306 display is turned off and on to reduce energy consumption.

Example

Here is an example how to use the Sleep class (a more detailed example is provided by SleepyPico.cpp):

const uint wakeup_pin = 15     // GPIO Pin to wait for high signal edges in DORMANT mode.
const bool edge       = true;  // we are waiting for a signal on the wakeup_pin.
const bool active     = true;  // wakeup_pin is in active high mode.


void setup() {
  // called once in the beginning: put your initialization code here
}

void loop() {
  // called in each iteration of the event loop: put your code
  // here to read sensors, control actuators, etc.
}

int main() {
  // stdio_init_all();
  sleep_ms(3000); // required by some OSs to make Pico visible in UARTs
  
  // Change frequency of Pico to a lower value (60 MHz)
  
  printf("Changing system clock to lower frequency: %d KHz\n", 60000);
  set_sys_clock_khz(60000, true);


  // Configure Sleep instance
  // Parameters:
  //     Lambdas for passing setup() and loop() 
  //     For SLEEP mode: Start and end of alarm period 
  //     For DORMANT mode: wakeup_pin where high edges are detected 
  //     as well as edge (true: wake up on leading edge; false: wakeup on trailing edge) and 
  //     active (true: Active HIGH; false: Active Low).
  
  Sleep::instance().configure(setup, loop, wakeup_pin, edge, active);
                              
  // Show clock frequencies:
  
  Sleep::instance().measure_freqs();
  
  // Start event loop.
  // This will call setup() once,
  // and then in each loop iteration
  //       put the Pico to sleep,
  //       call your loop() function.
  
  Sleep::instance().run(); 
  
  return 0;
 }

Warning

The current official SDKs for the Raspberry Pi Pico seem to work incorrectly regarding the sleep modes.

For example:

the Pico freezes after some (nondeterministic) time when using sleep modes.
UART output is not visible after sleeping.

This might also be due to missing documentation of the sleep modes, e.g., what needs to be done to recover from sleep. And, of course, it might be due to mistakes I made.

A simple but dirty workaround would be to add a reset button (between Pico GND and the RUN Pin) to your circuit.

How to build the app

To build this example application, execute

"cmake ."

and then

"make"

in the src directory.

Note: You'll find a precompiled sleepypico.uf2 in the subdirectory SleepyPico/bin

Circuit diagram

On the bottom left the BME280 sensor is depicted. The SSD1306 resides on the bottom right. The push button connected to 3.3V and GPIO 15 is used in DORMANT mode to wake up the Pico. The Pico is fed by a power supply (not shown) such as Mains, Solar Cell, LiPo, LiIon, or any other battery. For the weather station I am using a 18650 battery holder and a 18650 battery to power the circuit.

Measuring power consumption

Use an Ammeter/Multimeter or Oscilloscope for measuring power consumption. You need to place the Ammeter in series with the power source and the Pico.

Video demo

There is a short video on the operation of the circuit here. [Movie-File]: https://www.dropbox.com/s/l9ga78pulkpua55/SleepyPico-Demo.MOV?dl=0

ms1963/SleepyPico