Microcontrollers — the brain of a device

In one line

A microcontroller (MCU) is a whole tiny computer on one chip — processor, memory and I/O pins — built to run one program (its firmware) reliably, for years, on very little power.

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How it works

An MCU bundles everything on-chip and is built to be deterministic and low-power.

• CPU + memory — runs firmware from on-chip flash.
• GPIO pins — read a button or drive a transistor switching a motor.
• ADC — turns a sensor voltage into a number.
• Buses — I2C / SPI / UART, plus timers.

Where it shows up in digital health

• The glucose meter, pulse oximeter, smart inhaler, wearable — each is an MCU reading a sensor, computing, and sending it over BLE to a phone.
• Safety-critical devices run certified firmware under IEC 62304.
• It's the bottom of the data chain that becomes FHIR Observations.

Watch for

MCU firmware is a medical device when it makes clinical decisions — it carries the full weight of design controls and traceability, not just "code."