Mastodawn

BLE allows configuring events intervals - a key factor for optimizing energy use. By tuning these intervals, it’s possible to cut power consumption even further, which is crucial for a charging-free smartwatch.
#BLE #BluetoothLowEnergy #EnergyEfficiency #EmbeddedSystems

Dominik Oct 20

I tested the power consumption of BLE connection events on the STM32WB55. Each event draws only 3.29 mA and lasts about 3 ms—a great result for an ultra-low-power smartwatch design. (See attached image for details.)
#BluetoothLowEnergy #STM32 #LowPower

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Dominik Oct 15

After deeper reconfiguration of the MCU and peripherals before entering STOP mode, I brought it down to under 20 µA. Lesson learned: just enabling a sleep mode isn’t enough - extra tuning and clever hacks are essential for true low power.
#LowPowerDesign #EmbeddedSystems #Microcontroller

Dominik Oct 15

When I first tested STOP mode on the MCU (before adding any features), power consumption matched the documentation. But once I added peripherals and some functionality, it jumped to 370 µA.
#CortexM #STM32 #LowPower #Firmware

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Dominik Sep 30

STM32 also provides a clever setup: two integrated MCUs—one dedicated to BLE, the other for the application. This division helps cut power consumption even further.

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Dominik Sep 30

The second step is picking the right chip. After research, I found that Nordic and STM32 offer the lowest-power BLE solutions. Nordic is slightly better on paper, but I chose STM32 as I have more experience with it.

#LowPower #STM32 #NordicSemiconductor

Dominik Sep 30

Bluetooth is another major energy consumer in a smartwatch. Careful planning here can save a lot of power. The first step: use BLE only, never classic Bluetooth. #Smartwatch #BLE #BluetoothLowEnergy #LowPower #WearableTech

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Dominik Sep 20, 2025

I tested a 10×2.7 mm ERM motor to measure its current draw at different PWM duty cycles. The results are shown in the attached graphic. For typical smartwatch use, this translates to ~0.35 mAh per day
#Haptics #ERM #EccentricRotatingMass #EmbeddedSystems

Dominik Sep 20, 2025

I continue work on my charging-free smartwatch. The next component to tackle is haptic feedback. Two main options: ERM or LRA. LRA uses less power but needs an extra driver, so I decided to go with ERM. #Haptics #LowPower #Smartwatch #ERM

Dominik Sep 16, 2025

I chose an ultra-low power Cortex-M3 80 MHz from STM. It offers several sleep modes to save energy when idle. In my real-life tests, it showed just 3.35 µA in STOP mode and 10.18 mA in RUN mode—excellent results for this project.
#LowPower #EmbeddedSystems #CortexM #MCU #STM32