December 25, 2023

Exploring Power Management Techniques on the nRF52

Power management is a crucial aspect of any IoT device, especially for battery-powered devices. In this blog post, we will dive into power management techniques for the nRF52 series microcontrollers, which are widely used in the IoT community. We will explore various techniques and provide extensive examples and explanations to help you optimize power consumption in your projects.

Why Power Management Matters

Efficient power management is essential for extending the battery life of IoT devices, reducing costs, and enabling sustainable operation in remote locations. By optimizing power consumption, we can design devices that can run for months or even years on a single battery charge.

Power Modes

The nRF52 series microcontrollers provide multiple power modes to save energy. The most commonly used power modes are:

1. Active mode: This is the default mode where the device performs its primary functions. While in this mode, the microcontroller consumes the maximum amount of power, so it is essential to transition to other power-saving modes when idle or performing low-power tasks.

2. Sleep mode: Sleep mode disables the CPU while maintaining peripheral operation. The microcontroller can quickly wake up from this mode when it receives an interrupt, reducing power consumption significantly.

3. Deep sleep mode: In deep sleep mode, most of the peripherals and clocks are disabled, resulting in minimal power consumption. The microcontroller can wake up from this mode through external interrupts or real-time counters.

Power Management Techniques

Clock Management

Reducing clock frequency is an effective way to save power. By lowering the clock frequency, we can decrease the number of clock cycles required for executing instructions, reducing overall power consumption. For example, we can utilize the NRF_CLOCK API to reduce the system clock frequency.

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// Set the system clock frequency to 16MHz
NRF_CLOCK->TASKS_HFCLKSTART = 1;
while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}

NRF_CLOCK->HFCLKCTRL = CLOCK_HFCLKCTRL_HCLKDIV_2;

// Sleep to allow the changes to take effect
__WFE();
__SEV();
__WFE();

Peripheral Management

Disabling unnecessary peripherals when not in use can significantly reduce power consumption. For example, if a project only requires UART functionality during specific intervals, we can disable the UART peripheral when it is not needed and wake it up when necessary.

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// Disable UART when not in use
NRF_UART0->ENABLE = UART_ENABLE_ENABLE_Disabled;

// Wake up UART when required
NRF_UART0->ENABLE = UART_ENABLE_ENABLE_Enabled;
NRF_UART0->TASKS_STARTTX = 1;

Using Low-Power Modes

We can utilize sleep and deep sleep modes to save power during idle periods. By putting the microcontroller to sleep, we can reduce the active power consumption significantly. Here’s an example of entering sleep mode:

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__SEV();
__WFE();
__WFE();

And here’s an example of entering deep sleep mode:

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NRF_POWER->SYSTEMOFF = 1;

// Wake up through interrupts
...

Optimizing Interrupt Handling

Handling interrupts efficiently is vital for power management. Unoptimized interrupt handling can lead to excessive CPU wake-ups, resulting in increased power consumption. It’s important to process interrupts quickly and return to the low-power mode as soon as possible.

Conclusion

Optimizing power management is crucial for designing efficient and long-lasting IoT devices. By utilizing techniques such as clock management, peripheral management, low-power modes, and optimizing interrupt handling, we can significantly reduce power consumption on the nRF52 microcontrollers. Consider these techniques to extend battery life, reduce costs, and create sustainable IoT solutions.

Remember, the examples provided are just a starting point, and you should adapt them based on your specific project requirements.

➡️ Debugging techniques for nRF52 applications

⬅️ Introduction to the nRF52 SoftDevice: architecture and concept

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