Designing Low-Power Bluetooth LE Products

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Design
Lesson 1 – Power consumption essentials
4 Topics | 1 Quiz
A typical Bluetooth LE product architecture
Bluetooth LE communication methods
Electrical quantities
Exercise 1 – Estimating power budget
Lesson 1 quiz
Lesson 2 – Designing with a Nordic PMIC
7 Topics | 1 Quiz
PMIC overview
System management features with Nordic PMICs
System efficiency considerations
PMIC hardware integration
PMIC software integration
Getting started with Nordic PMICs
Exercise 1 – Powering nRF54L devices from a single AA/AAA battery
Lesson 2 quiz
Measure
Lesson 3 – Tools and best practices for power measurement
5 Topics | 1 Quiz
Current measurement fundamentals
Current measurement equipment: Capabilities, limitations, and best practices
Measurement setup validation and error mitigation
Exercise 1 – Setup verification using System OFF
Exercise 2 – Bluetooth LE advertising power profiling and data extrapolation
Lesson 3 quiz
Optimize
Lesson 4 – Bluetooth LE power optimization
4 Topics | 1 Quiz
Bluetooth LE advertising parameters and power consumption
Bluetooth LE connection parameters and power consumption
Exercise 1 – Optimizing power consumption during Bluetooth LE advertising
Exercise 2 – Optimizing power consumption in a Bluetooth LE connection
Lesson 4 quiz
Lesson 5 – SoC specific power optimization I
6 Topics | 1 Quiz
Clock sources
Peripherals
Memory retention and sleep modes
Exercise 1 – Estimating and measuring how clock sources affect power consumption
Exercise 2 – Comparing current consumption of peripherals from different power domains
Exercise 3 – Measuring the impact of RAM retention settings
Lesson 5 quiz
Lesson 6 – SoC specific power optimization II
6 Topics | 1 Quiz
GPIO interrupt types on the nRF54L Series
DPPI Distributed programmable peripheral interconnect
Direct Memory Access (EasyDMA)
Exercise 1 – Measuring sleep current with different GPIO interrupt types
Exercise 2 – Reducing CPU activity by connecting peripherals with DPPI
Exercise 3 – Reducing current consumption with EasyDMA
Lesson 6 quiz
Monitor
Lesson 7 – Remote monitoring of Bluetooth LE devices with nRF Cloud
8 Topics | 1 Quiz
Why remote observability matters for low-power Bluetooth LE devices
Key data points for Bluetooth LE connection stability and power efficiency
Integrating the Memfault SDK into a Bluetooth LE peripheral application
Fleet-wide analysis and debugging with nRF Cloud
Exercise 1 – Setting up the Memfault SDK on an nRF54L Series DK
Exercise 2 – Exploring the automatically collected Bluetooth LE metrics
Exercise 3 – Observing the impact of connection parameter changes on metrics
Exercise 4 – Invoking a firmware update over Bluetooth LE (OTA)
Lesson 7 quiz
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Exercise 3 – Reducing current consumption with EasyDMA

This exercise demonstrates how EasyDMA can reduce the current consumption by offloading the CPU in the data operation process. For simplicity, the PWM peripheral is used to generate the user-defined GPIO duty cycle pattern. The PWM output can be easily generated by using the Timer peripheral with minimal CPU involvement to change the duty cycle.

Note

This exercise has limited suppquipped with the ort for the following SoCs:

  • nRF54LV10: The SoC is not ePWM peripheral.

The nRF54L Series SoC is also equipped with a dedicated PWM peripheral with a duty cycle sequence decoder, which uses EasyDMA for the operation. As the PWM peripheral is designed and optimized to benefit from EasyDMA operation, it is the default and recommended way of using the peripheral. The Timer peripheral (with DPPI) is used to show the base current consumption and present the benefits of using the dedicated peripheral using EasyDMA to generate complex GPIO patterns.

The exercise covers executing a predefined GPIO pattern using the following peripherals:

  • The Timer peripheral (with DPPI to simulate PWM) and the CPU for the duty cycle change
  • The PWM peripheral with EasyDMA to execute the pattern without CPU involvement
  • The PWM peripheral with EasyDMA and double buffering to run multiple patterns with minimal CPU involvement

Pattern

The pattern used in the exercise contains predefined 5000duty cycle values. It is stored in the RAM as a look-up table (pattern.c file), and the next value is loaded at the 16 kHz frequency. LED1 (on the nRF54L15 DK) is used to visualize the pattern presented by the following chart.

Exercise steps

In the GitHub repository for this course, go to the base code for this exercise, found in l6/l6_e3.

As in previous exercises, you will need a Power Profiler Kit II (PPK2) connected to the DK.

1. Using the Timer peripheral to visualize the GPIO pattern on LED1.

1.1 Build and flash the application to your DK.

The timer is enabled in the exercise base by default, so we just need to build and flash it to observe the current consumption.

As the pattern is not enabled yet, you will see the current consumption for the timer in the peripheral power domain. As the pattern generation is not included yet, you cannot see any change in the LED behavior.

1.2 Enable pattern execution.

Set the timer to execute the pattern in the prj.conf file:

Copy
CONFIG_PATTERN_TIMER_W_CPU=y
Kconfig

Note

The PWM peripheral uses DMA by default. As the PWM peripheral contains the counter for its operation, the Timer/Counter peripheral is used as a base for current consumption comparison. The timer is configured to use DPPI to change the GPIO state to make the configuration close to PWM peripheral (or the Timer with dedicated PWM mode, present in some other SoCs on the market). The only CPU involvement is to change the compared channel settings on every period, at 16 MHz frequency (which is the same for the PWM peripheral in this exercise). Measure how much the current changes due to this involvement. The next steps demonstrate how the PWM peripheral can reduce the CPU involvement (allowing for a decrease in current consumption ) by using the built-in DMA sequence decoder.

The timer runs at 16 MHz frequency and uses two channels:

Channel 0 – the compare register is set to value 1000. The compare event occurs at 16 kHz frequency and includes the following actions:

  • Clear the timer counter (using DPPI shortcut)
  • Clear LED GPIO (using DPPI shortcut)
  • Load next duty cycle value from the lookup table (channel 1 compare register)

Channel 1 – the compare register contains the pattern value (duty cycle). When the compare event occurs, the GPIO LED is set (using DPPI shortcut) and stays lit until the end of the period.

The following flowchart presents the behavior of the system:

1.3 Build and flash the application to your DK.

The LED1 smoothly changes the brightness periodically. As the CPU changes the brightness of the LED at a 16 kHz frequency and the CPU changes the duty cycle every period, there is a significant increase in current consumption by more than 200 µA.

2. Using the PWM peripheral with EasyDMA to run the pattern.

Now, you can use the PWM peripheral to run GPIO pattern. This way, you only need to configure the PWM to work with the selected RAM region where the pattern is stored. After starting, the peripheral will automatically update the duty cycle without CPU involvement. Thanks to the DPPI short connection (LOOPSDONE_DMA_SEQ[i]_START), the pattern restarts automatically.

2.1 Enable the PWM with EasyDMA for the pattern execution in prj.conf file:

Copy
CONFIG_PATTERN_PWM_SIMPLE=y
Kconfig

2.2 Disable CPU involvement in generating the pattern by:

Copy
CONFIG_PATTERN_TIMER_W_CPU=n
Kconfig

2.3 Build and flash the application to your DK.

Observe how the LED is blinking and measure the current consumption results. The current consumption has been reduced significantly. The average current is quite close to the Timer (located in the peripheral power domain) running at 16 MHz. In the previous step, it was calculated that the CPU involvement at this frequency itself increases the current consumption by 200 µA. Using the PWM with EasyDMA allows you to achieve current consumption way below that level, and the value contains the peripheral running plus changing the duty cycle every period.

3. Using the PWM decoder with two sequences to run multiple patterns.

In this step, you will use the PWM decoder, which can run two sequences in a loop. Each of the sequences can be asynchronously updated (when it is not executed at the time of update). This way, you can execute many LED patterns with minimal CPU intervention (only for selecting the pointer to the next pattern RAM region).

The following image demonstrates the usage of two sequences to run three sample patterns. The CPU is needed only to configure the inactive sequence for using the selected pattern.

Use the PWM with an integrated EasyDMA decoder to run the following LED brightness characteristic in a loop:

3.1 Enable the PWM complex pattern execution.

Enable complex pattern execution in the prj.conf file:

Copy
CONFIG_PATTERN_PWM_COMPLEX=y
Kconfig

3.2 Disable Kconfig from the previous step.

Copy
CONFIG_PATTERN_PWM_SIMPLE=n
Kconfig

3.3 Build and flash the application to your DK.

Observe the LED blinking and the current consumption. Due to the minimal involvement of the CPU, the current consumption has changed significantly.

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      Change summary

      What's new in the latest version

      General updates

      General updates

      •Support for nRF54LS05 DK (Available through the early access sampling program)
      •Support for the nRF54LM20B with Axon NPU for Edge AI applications
      Bluetooth LE updates

      Bluetooth LE updates

      •Quality of Service module is now production-ready.
      •New experimental features for RF testing (Direct Test Mode) and low-latency packet handling (LE Flushable ACL).
      MCUboot & Partition Manager

      MCUboot & Partition Manager

      •Single-Slot DFU and RAM Load mode are both promoted to fully supported
      •Partition Manager is officially deprecated in favor of Zephyr's devicetree-based partitioning.