Technical Articles
2025-01-15

Low Power Design Strategies in RTOS Environments

Do you all know if anyone has ever worked on low-power products?
Low-power products may seem simple, but to create a good low-power product, especially achieving ultra-low power, is relatively more challenging.
Today, we will discuss the design strategies for low power in RTOS environments.

Preface: Programming Mindset

The design of embedded products is diverse and customizable, often requiring a combination of needs to achieve hardware and software design.
Perhaps the software architecture you write can be reused in “similar” products, but if the span is too large, your software architecture may not be applicable.
However, there are many similarities in embedded software design; even if the software architecture cannot be used, the design thinking is still applicable.
Low Power Design Strategies in RTOS Environments
It’s like: once you learn a skill, if one company doesn’t want you, another will, even if the products designed by the two companies are different.
Therefore, having a good programming mindset is crucial, including software architecture, programming modules, low coupling, and high cohesion.
Returning to the low power design strategies in RTOS, there are commonly two types:

  • Regular Low Power: Enter low power mode while running Idle tasks.

  • Ultra Low Power: Enter low power mode in idle state, waking up through interrupts or external events.

Regular Low Power

Regular low power means that the processor intermittently enters a low power state but will wake up periodically; this kind of power consumption cannot be very low.
In RTOS, this regular low power is typically achieved when the task is in Idle (idle task).
Rough schematic:
Low Power Design Strategies in RTOS Environments
The rough idea is: Idle tasks periodically enter low power, but will periodically wake up to check if there are higher priority tasks responding. While in low power state, the processor can also be woken up by external events or interrupts.
Tip: Some RTOS can perform low power operations through “HOOK functions”. Additionally, some RTOS’s idle tasks may require some configuration.

Ultra Low Power

The method above, which periodically wakes up the CPU, cannot achieve ultra-low power, even if there is nothing else to do, the CPU still has to wake up to “take a look”.
To achieve ultra-low power, do not disturb the CPU when there is nothing to do; wake it up only when there is something.
Rough schematic:
Low Power Design Strategies in RTOS Environments
This way of the CPU entering “deep low power” differs from the above and is related to the CPU’s low power modes.
For example: sleep, shutdown, standby, etc. Different processors may have different low power modes; how to implement and wake them up should be combined with the specific CPU implementation methods.
Low Power Design Strategies in RTOS Environments

Finally

Designing low power products is relatively more challenging and requires a combination of hardware and software to solve various “power consumption anomalies,” but the overall application is not complicated.
Of course, there are more methods to achieve low power: for example, frequency reduction, zero-power standby, etc. Everyone is welcome to leave comments to share how your products achieve low power.

Source: strongerHuang

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Low Power Design Strategies in RTOS Environments

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