English for Embedded and Hardware Engineers: Firmware, RTOS, and IoT Vocabulary

Embedded and hardware engineering has its own precise vocabulary that differs significantly from web or cloud software. When working with international teams, reviewing datasheets, or writing technical specifications, you need to use this vocabulary correctly. This guide covers the three main vocabulary areas: embedded systems, IoT, and hardware-software interface communication.

Core Embedded Systems Vocabulary

Firmware — software that is permanently programmed into a read-only memory device in a piece of hardware. Unlike application software, firmware is tightly coupled to the specific hardware it runs on. “After flashing the firmware update, the sensor began reporting accurate readings.”

RTOS (Real-Time Operating System) — an operating system designed to serve real-time applications that process data and events with precisely defined timing constraints. Common RTOSes include FreeRTOS, Zephyr, and VxWorks. “We switched to FreeRTOS because bare-metal scheduling was becoming unmanageable as we added more tasks.”

Interrupt — a signal to the processor that immediately suspends the current task and executes a special handler function (an ISR — Interrupt Service Routine). Interrupts are triggered by hardware events such as a button press, timer overflow, or incoming data. “The UART interrupt fires every time a byte arrives from the GPS module.”

ISR (Interrupt Service Routine) — the function that runs in response to an interrupt. ISRs must be short and fast; lengthy processing should be deferred to a task queue. “Keep ISRs under 10 microseconds; post a flag to a task for the heavy lifting.”

Peripheral — a hardware component connected to a microcontroller core, such as a UART, SPI bus, I2C controller, ADC, or GPIO. “We use the SPI peripheral to communicate with the external flash memory at 20 MHz.”

HAL (Hardware Abstraction Layer) — a software layer that provides a standardised interface to hardware peripherals, allowing higher-level code to be more portable across different microcontroller families. “By using the HAL driver for the ADC, we were able to port the codebase from STM32F4 to STM32H7 in a single afternoon.”

MISRA C — a set of software development guidelines for the C programming language, developed by the Motor Industry Software Reliability Association. Widely required in safety-critical systems. “The automotive client requires full MISRA C:2012 compliance; our static analyser flags any deviations.”

Bare metal — programming without any operating system, writing directly to hardware registers. “The first prototype ran bare metal; we added FreeRTOS once we needed concurrent task management.”

Watchdog timer — a hardware timer that resets the microcontroller if the software fails to periodically send a reset signal (a “kick”). Used to recover from software deadlocks or crashes. “If the main loop hangs for more than 500 ms, the watchdog resets the system automatically.”

IoT Vocabulary

MQTT (Message Queuing Telemetry Transport) — a lightweight publish-subscribe messaging protocol designed for constrained devices and unreliable networks. Devices publish data to a broker; subscribers receive it. “The sensor publishes temperature readings every 30 seconds to the MQTT broker over a 2G connection.”

Edge computing — processing data on or near the device where it is generated, rather than sending it all to the cloud. Reduces latency and bandwidth costs. “We moved anomaly detection to the gateway using edge computing; only flagged events are sent to the cloud.”

Sensor fusion — combining data from multiple sensors to produce a more accurate or complete measurement than any single sensor could provide. “The IMU combines accelerometer, gyroscope, and magnetometer data using a Kalman filter for sensor fusion.”

OTA (Over-the-Air) — updating firmware or configuration wirelessly, without physical access to the device. “The OTA update mechanism includes a rollback capability in case the new firmware fails to boot.”

Device provisioning — the process of configuring a new device with credentials, certificates, and initial settings before or during its first deployment. “Each device goes through automated provisioning in the factory; by the time it reaches the customer, it is pre-enrolled in our device management platform.”

Hardware-Software Interface Communication

When engineers from different disciplines collaborate, misunderstandings often arise from terminology differences. Use these phrases to communicate clearly across the hardware-software boundary.

Discussing register-level behaviour:

• “The enable bit is in register 0x3C, offset 4. Writing a 1 to that bit starts the conversion.”
• “We need to ensure the GPIO is configured as an output before calling the initialisation function.”

Describing timing constraints:

• “The chip requires a minimum of 10 µs between the chip select assertion and the first clock edge.”
• “The ISR must complete before the next timer tick, which fires every 1 ms.”

Reporting hardware anomalies:

• “Under load, we are seeing intermittent NACK responses on the I2C bus — possibly a timing violation or a pull-up resistor issue.”
• “The ADC readings show a 50 Hz noise component, which suggests ground loop interference from the power supply.”

Example Sentences in Context

1. “We discovered that the watchdog was firing in production because the RTOS task responsible for kicking it was being starved by a lower-priority task that held a shared mutex indefinitely.”

2. “The HAL abstraction allowed us to reuse 90% of our driver code when migrating to the new microcontroller family, reducing the porting effort from an estimated three weeks to two days.”

3. “Because the device operates over NB-IoT with a constrained data allowance, we implemented sensor fusion locally and only transmit a summary event when the fused output crosses a defined threshold — this is the core of our edge computing strategy.”

4. “MISRA C compliance is non-negotiable for this medical device project; every deviation requires a documented justification approved by the safety manager before it can be accepted.”

5. “The OTA update process uses a dual-bank flash layout: new firmware is written to the inactive bank while the device keeps running on the active bank, then a single atomic switch occurs on the next reboot.”

Vocabulary for Technical Documentation

When writing embedded documentation — whether a datasheet annotation, a software requirements specification, or a hardware interface document — use precise, unambiguous language:

• Prefer “shall” for mandatory requirements, “should” for recommendations, and “may” for optional behaviour.
• Always specify units: “200 µs” not “200 units.”
• Define every acronym on first use, even if it seems obvious — cross-discipline readers will thank you.

Embedded engineers who communicate clearly across hardware-software and firmware-application boundaries are significantly more effective than technically brilliant engineers who cannot articulate their constraints. Invest in this vocabulary and it will pay dividends throughout your career.