Wireless remote that wakes instantly when picked up, no button press to turn it on. Had to fit a specific curved enclosure shape.
The Solution
TI CC2640 BLE SoC with an LIS2DH accelerometer configured for motion interrupt wake. The accelerometer draws ~2µA in low-power mode and wakes the CC2640 from shutdown on any movement. Custom-shaped PCB follows the enclosure contour to maximize battery volume. PCB trace antenna with a u.FL test port for antenna characterization in the actual enclosure.
Results
Users just pick it up and it's connected within 200ms. Battery lasts several months because the device spends most of its life in shutdown at ~1µA.
How it wakes up
The accelerometer is the only part awake. It watches for movement at about 2 µA and wakes the CC2640 from shutdown when the remote is picked up, so the device spends almost its whole life near 1 µA and still connects within 200 ms.Instant response without paying for it. A remote that is always advertising quickly enough to feel instant spends most of its battery on advertising nobody hears. Sleeping in shutdown with the accelerometer as the only thing awake keeps the idle draw at about 3 µA, yet still connects within 200 ms, which works out to roughly 23 times less current than fast advertising at 20 uses a day.
Have a Similar Challenge?
Low-power wireless with custom form factors is a regular design task.
