Glossary.
The terms the rest of this site uses, defined for the person signing the contract rather than the engineer doing the work.
- Agile
- A way of running development in short cycles, where the plan is revisited as the work teaches you things. We use it for firmware and software, where changing direction costs a rebuild rather than a new set of boards.
- AOSPAndroid Open Source Project
- The open version of Android, used on devices that need a full operating system but are not phones. Building on it means taking Android and adapting it to specific hardware.
- Bed-of-nails fixture
- A test jig with an array of spring-loaded pins that press onto test points on a bare board. The operator drops a board in, closes the lid, and the fixture checks every circuit in a few seconds. One is usually built per board in a product.
- BLEBluetooth Low Energy
- The low-power version of Bluetooth that battery devices use to talk to a phone. It is what lets a product run for months on a coin cell and still pair with an app.
- BOMbill of materials
- The list of every part in a product, with the quantity and the specific part number for each. It is where unit cost comes from, and where supply problems show up first.
- Bring-up
- The first time firmware runs on a new board. Power comes up one rail at a time, each interface is proven in turn, and the assumptions hardware and firmware made about each other get tested against reality.
- CANCAN bus
- A rugged two-wire bus that lets several boards in one machine talk to each other. Common in vehicles and industrial equipment because it survives electrical noise and long cable runs.
- Contract manufacturerCM
- The factory that builds your product. You own the design; they own the line, the people and the equipment. Most consumer hardware is built this way rather than in a factory the brand owns.
- DFMdesign for manufacturing
- Changing a design so a factory can build it repeatably at volume — part placement a machine can reach, tolerances a line can hold, test points where a fixture can touch them. A design that works on the bench is not automatically a design that can be built ten thousand times.
- DSPdigital signal processing
- The math that turns a messy sensor reading into a usable fact — that a case was opened, that a heart beat. It runs on the device, which means it has to be accurate and cheap in power at the same time.
- DVTdesign validation test
- The build after EVT, in larger numbers and with production tooling. The question it answers is whether the product meets its specification and passes certification — drop tests, temperature, radio compliance.
- EVTengineering validation test
- The first build at the factory, in small numbers. The question it answers is whether the design works at all when somebody other than the design team assembles it.
- Firmware
- The software that runs on the product itself rather than on a phone or a server. It starts when the device powers on and is responsible for everything the hardware does.
- Form factorFF
- The phase where the boards take their final shape and size, so they fit the enclosure the mechanical team has designed. Before this phase the electronics are deliberately the wrong shape — see non-form factor.
- FPCAflexible printed circuit assembly
- A circuit built on a bendable substrate instead of a rigid board, so it can wrap around a curve or fold into a tight space. Used where a rigid board simply would not fit.
- Hardware abstraction layerHAL
- A layer of firmware that hides the specifics of a chip from the code above it. With one in place, a new revision of the board — or a different chip entirely — changes one layer instead of the whole application.
- I2C
- A two-wire bus used to connect sensors and small chips to a microcontroller over short distances inside one product. Each device on the bus needs its own address, which is a common source of conflicts.
- IO-Link
- A standard for connecting industrial sensors and actuators to a controller over ordinary cabling, including configuration and diagnostics rather than just a raw signal.
- JDMjoint development manufacturer
- A factory that also does design work, so it can take ownership of a finished design and make the changes a production line needs. Handing a design to a JDM is one of the ways a project ends.
- MCOmechanical control outline
- The drawing that fixes where the electronics are allowed to be: board shape, keep-out zones, connector and button positions, mounting points. It is the contract between the electrical and mechanical teams.
- MCUmicrocontroller
- The processor at the center of most embedded products — a chip with the processor, memory and peripherals in one package. Choosing it fixes a lot of the rest of the design.
- Non-form factorNFF
- A deliberately oversized first board, built to prove the architecture before anyone is constrained by the enclosure. Spreading the circuit out makes it easy to probe, rework and change, which is the point.
- OTA updateover-the-air update
- Updating the firmware on a device that is already in a customer’s hands, over Bluetooth or the internet. It has to be designed in from the start, and it has to be impossible to leave a device unable to boot.
- PCBAprinted circuit board assembly
- A circuit board with all its components soldered on — the finished electronics, as opposed to the bare board. Most products contain more than one.
- PMICpower management integrated circuit
- The chip that takes one input — a battery, a USB cable — and produces the several different voltages the rest of the product needs, at the right times and in the right order.
- POSIX
- The shared set of interfaces behind Linux and the other Unix-like systems. Code written against it runs on more than one of them, which matters on products where the operating system choice can change.
- PPGphotoplethysmography
- Measuring heart rate by shining light into the skin and reading how much comes back as blood moves. The sensor is cheap; the difficulty is in the signal processing.
- PVTproduction validation test
- The last build before mass production, run on the real line at close to real speed. The question it answers is whether the factory can build the product, not whether the product works.
- PWMpulse-width modulation
- Controlling how much power something gets by switching it on and off very fast and varying the proportion of on to off. It is how LEDs dim, motors change speed and heaters hold a temperature.
- RFradio frequency
- The part of a design that sends and receives radio — antenna, matching circuit, shielding and layout. It is the area where small layout mistakes cause failures that are hard to diagnose and expensive to fix late.
- RMAreturn merchandise authorization
- The process for handling units that come back from customers, and the engineering work of finding out why. Patterns in returns are the fastest signal that something on the line or in the design is wrong.
- RTOSreal-time operating system
- A small operating system for embedded devices that guarantees certain work happens within a fixed time. Used where late is the same as wrong — a motor control loop, a safety cut-out.
- SMPSimple Management Protocol
- The protocol Zephyr devices use to be managed over a wire or a radio link: firmware upgrade, file transfer, reset, statistics. Our open-source smpclient and smpmgr implement it.
- Statistical process controlSPC
- Watching the measurements coming off a production line for drift, so a process is corrected before it starts producing failures rather than after. It depends on the test fixtures recording real numbers, not just pass and fail.
- TDDtest-driven development
- Writing the test before the code it checks. On firmware it has a particular value: the tests run on a PC from the first week, so the software schedule does not have to wait for hardware to exist.
- UART
- A simple two-wire serial link between two chips or between a device and a computer. Old, universally supported, and still the first thing connected at bring-up.
- USB PDUSB Power Delivery
- The standard that lets devices negotiate over USB-C for more power than the default — up to 240W. Each offer in the negotiation is a PDO, and a device can change its offers as conditions change.
- USB PD alt mode
- A part of the USB-C standard that lets the pins in the connector carry something other than USB. It is how a cable can carry DisplayPort — or, on the iFixit Power Station, our own high-speed link to the Soldering Iron.
- Waterfall
- Running a project as a sequence of phases, each largely finished before the next begins. We use it for hardware, where a change after layout means new boards, new lead times and new money.
- Zephyr
- An open-source real-time operating system for embedded devices, run by the Linux Foundation and supported by most of the major chip vendors. Our open-source tools target devices running it.
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Looking for how a project actually runs? That is on How we work and in the questions.