32bit ARM Cortex in a watch


Uwatec has designed an ARM Cortex-M3 32bit microcontroller from Energy Micro into its Meridian diving computer.

Energy Micro is known for designing extremely low power peripherals for its microcontrollers.

This particular one, an EFM32G890, has a 0.55µA LCD controller, runs at 32MHz at under 6mA, and has five sleep modes (three under 1µA) – some of which allow peripherals to talk to each other with the core off.

Running on a CR2032 cell, Meridian is designed for use at 120m depth (aided by a sapphire front window) and runs an algorithm to manage multi-gas decompression that takes account of heart rate.

“Our adaptive algorithm, which accounts for the effects of workload, micro bubbles and temperature for every dive, is more advanced than basic time/pressure based diving algorithms. However, the added complexity requires 32bit calculation power and energy efficiency,” said Reima Holopainen, R&D manager of Uwatec.

While diving, the Meridian can be configured to display dive information including depth, dive time, decompression status, and water temperature.

“It operates in three modes: apnea, scuba or gauge, and can store over 50 hours of diving data. The dive profiles can be downloaded, edited and reviewed on a personal computer,” said Uwatec.

Above the surface it handles remaining de-saturation time, no-fly time, and features a built in thermometer and altimeter for mountain walking.

Tags: ARM, Cortex, Energy Micro, Gecko

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