What to Prepare Before Hiring an Embedded Engineer (Checklist)

Before you talk to an embedded engineer or agency, write down twelve answers about the device's job, location, cost, and ownership. An embedded engineer writes the code that runs on the chip inside a device, and often designs its circuit board. Each blank becomes a paid question, or a guess you later pay to undo.

Hardware schedules slip often. In Ethan Mollick's study of Kickstarter projects from 2009 to 2012, only 24.9% of funded Technology and Design projects delivered on time. The interviews he cites name changes in scope and unanticipated certification issues among the causes. Rows 2 and 8 of the checklist address both before the first invoice.

Embedded engineer checklist: 12 answers to prepare

#	Prepare	Example of a usable answer	What a blank costs you
1	Problem and user scenario	"A user checks the device 3 to 15 times a day"	Power and radio estimates rest on guessed usage
2	Must-have vs nice-to-have features	Each feature marked Must, Should, Could, or Won't	Scope grows, and the budget ends before the must-haves are proven
3	Power source and battery-life target	"Rechargeable, 3 months per charge"	The chip and radio get chosen twice
4	Connectivity and where the device lives	"Garden shed, 25 m from the home router, one reading per hour"	The radio fails at the real location
5	Environment	"Outdoors, rain, direct sun, −20 °C to 40 °C air"	Parts or enclosure fail in heat, cold, or water
6	AI feature: on the device or in the cloud	"Classify the reading on the device, also when offline"	A chip that cannot run the model, or a cloud bill per device
7	Target unit cost and quantity	"Under $40 in parts, first batch of 500"	A prototype that cannot be built at your price
8	Markets you will sell in	"US and EU in year one"	Certification surprises and a late board change
9	Definition of done	Three to five pass-or-fail tests with numbers	Paying for work nobody agreed was finished
10	Existing assets	Sketches, competitor products, their FCC IDs	The engineer bills hours to research what you already know
11	Budget and timeline	A budget range and one hard date	Quotes you cannot compare, and scope cut in the wrong place
12	Ownership	Code, design files, and cloud and app accounts in your company's name	Paying again to get your own product back

Fill rows 1, 6, and 7 first, because other rows depend on them. The scenario sets wake-ups, which set battery life; the AI choice sets the chip, which sets battery life and unit cost.

User scenario: write a day in the life, with counts

The user scenario describes who uses the device, where, and how often. Write it as one day in the life, with counts: how many uses, and what the device does each time.

Those counts become engineering inputs. Ring's support documentation, for example, lists motion events, Live Views, cold weather, and weak Wi-Fi as causes of battery drain in its doorbells. Each is a fact about the user's home, not about the circuit board.

Write down a busy day and a quiet day, because the device has to survive the busy one.

Must-have features vs nice-to-have: sort them before the quote

The DSDM agile framework sorts requirements into Must Have, Should Have, Could Have, and Won't Have this time (MoSCoW). Must Haves are the "Minimum Usable SubseT": without them, the product is not viable, legal, or safe. DSDM recommends no more than 60% of the effort on Must Haves.

An unsorted list turns every feature into a must, so the quote grows and nothing can be cut when a test fails.

Mark every feature M, S, C, or W, and expect the first prototype to cover the Musts.

Power source and battery-life target: one number narrows the chip

The power source is a wall adapter, building wiring, or a battery; the battery-life target is how long the device runs between charges.

Espressif lists 7 µA for the ESP32-S3 in deep sleep and 340 mA peak while it transmits Wi-Fi (datasheet v2.2). That is a ratio of about 49,000, so battery life depends on how often and how long the device wakes, which your user scenario sets.

On paper, 7 µA would let a 235 mAh CR2032 coin cell last about 3.8 years. Energizer, however, tests that cell with 6.8 mA pulses, not 340 mA bursts. A Wi-Fi device therefore needs a larger battery or a different radio.

Rechargeable lithium-ion cells add two limits. Battery University states that consumer Li-ion cells cannot be charged below 0 °C (32 °F). For air transport, IATA's 2026 guidance requires every lithium cell and battery type to pass the UN 38.3 tests. Untested pre-production prototypes shipped for testing may fly only on cargo aircraft, with approval from the national authorities involved (IATA B.04, Special Provision A88). Ask for a cell that already has a UN 38.3 test summary.

Write the battery target as days, weeks, or months, and say whether users will recharge or replace the battery.

Connectivity and location: the radio follows where the device lives

Connectivity is how the device sends data: Wi-Fi, Bluetooth Low Energy (BLE), LoRa, or cellular.

Wi-Fi carries photos and video, peaks at 340 mA on an ESP32-S3, and needs the user's network password. Passing that password from a phone, as Espressif's provisioning framework does over BLE, is app work that belongs in the quote.

BLE links the device to a nearby phone or hub, which relays data to the internet.

LoRaWAN, a protocol for small messages over long distances, carries 51 to 222 bytes per message in Europe's 868 MHz band. Its main sub-bands allow 1% transmit time, which suits sensor readings but not photos.

Cellular IoT uses LTE-M or NB-IoT, low-power 4G standards for devices, wherever an operator runs them. Each device needs a SIM plan; the IoT carrier 1NCE, for example, lists €12 for 10 years with 500 MB of data (October 2026). That is about 4 MB a month, enough for readings and not for video. GSMA guidance expects 2G and 3G machines to move to 4G and 5G, with Europe's main network closures in 2025 to 2027.

Write down where the device sits, its distance to a router or gateway, and what it sends: hourly readings, photos, or live video.

Environment: heat, cold, water, and sun

Enclosures carry IP codes defined by IEC 60529. IP67 means dust-tight and protected against immersion to 1 m for 30 minutes. The water ratings are not cumulative beyond IPX6, so an IPX7 device is not necessarily protected against water jets (IPX5 or IPX6). A device that will be sprayed with a hose needs a jet rating as well as an immersion rating.

Parts carry temperature ratings too, and the limits sit in variant tables. Espressif rates its ESP32-S3-WROOM-1 modules with 8 MB of extra memory (octal PSRAM) for −40 to 65 °C ambient. Other variants of the same module reach 85 °C or 105 °C.

A sealed box in the sun also runs hotter than the air around it. Wankhede et al. state that ignoring solar load can shorten an outdoor product's life or cause failure.

Write down the hottest and coldest spot, direct sun, and whether the device gets splashed, sprayed, or submerged.

AI feature: on the device or in the cloud

On-device AI means the chip inside the product runs the model. Cloud AI means the device sends data to a server, which runs the model and returns the answer. The choice moves cost between the unit price, the battery, and a monthly bill.

Small tasks fit on microcontrollers. The Visual Wake Words benchmark (Chowdhery et al., 2019) showed person-or-no-person image models reaching 85 to 90% accuracy within 250 KB of memory. That is less than half the 512 KB of on-chip SRAM in an ESP32-S3.

Larger tasks, such as language models, need a Linux-class module. NVIDIA launched its Jetson Orin Nano Super developer kit at $249 in December 2024. NVIDIA says it runs language models of up to 8 billion parameters. In its 25 W mode, a 37 Wh battery (10,000 mAh at 3.7 V) lasts about 1.5 hours, so this tier usually needs wall power.

Cloud AI keeps the device simple but adds a bill per use and needs a connection. Amazon Rekognition charges $0.001 per image for the first million images a month in US East (October 2026). A device that sends 100 images a day costs about $3 a month in image analysis, for as long as it is in use.

Write down what the AI must decide, how fast it must answer, and whether it must work without internet. Those three answers pick the tier, and our edge AI hardware comparison covers the chips in each.

Target unit cost and quantity: the price the design must hit

Target unit cost is what one finished device may cost to build; the bill of materials (BOM) lists every part with its price. Quantity changes both part prices and how the radio is built in.

A radio module carries the shielding and power regulation that FCC modular approval requires (47 CFR 15.212), so your product can reuse its certification. You pay for that in every unit. A chip-down design certifies your own board once, a fixed cost that shrinks per unit as volume grows.

Give a target parts cost and the size of the first batch, even as a range.

Markets: where you sell decides certification

United States. With limited exceptions, every product that intentionally transmits radio must be certified before it is marketed (47 CFR 15.201). A pre-certified module helps, but the host product still needs Part 15 Subpart B testing for unintended emissions. It also needs a "Contains FCC ID" label, per FCC guidance summarized by module maker Ezurio.

European Union. The Radio Equipment Directive's cybersecurity rules have applied to internet-connected radio products since 1 August 2025. The Cyber Resilience Act (CRA) replaces them on 11 December 2027, and the CRA's reporting obligations have applied since 11 September 2026.

EU batteries. From 18 February 2027, Article 11 of the EU Battery Regulation requires portable batteries in products to be "readily removable and replaceable by the end-user". Removal must work with commercially available tools, without heat or solvents. A narrow exception covers appliances designed to operate mainly where they are regularly splashed, sprayed or immersed, and intended to be washed or rinsed. Even then, an independent professional must be able to replace the battery (Art. 11(2)).

Certification is per market, and a market added late can force a board or enclosure change. List your first-year countries before the design starts.

Definition of done: success criteria for the prototype

A works-like prototype proves the device functions; Instrumental's handbook places the first build that combines final appearance and function later, at EVT (engineering validation test).

Write three to five pass-or-fail tests with numbers, such as:

• "Sends a reading every hour for 7 days without a missed message."
• "Runs 14 days on battery in a bench test."
• "The app shows a new reading within 3 seconds."

Without written tests, "done" gets argued after the money is spent. Attach the tests to the contract, and ask for results at handover.

Existing assets: sketches, competitors, and FCC filings

Bring sketches, user flows, photos of similar products, and any code or parts you already tried.

Radio products certified for the US show an FCC ID on a physical label or an e-label. The public filing behind that ID can include test reports and internal photos (FCC TCB workshop, April 2016).

Send a list of competitor products with their FCC IDs, and say what you want to do better than each one.

Budget and timeline: a range and one hard date

Give a budget range and one fixed date, such as an investor demo; what a smart-device prototype costs helps set the range. DSDM fixes time, cost, and quality and negotiates features, so your MoSCoW list tells the engineer what to cut first.

Some delay sits outside engineering. Apple asks companies enrolling in its Developer Program for a D-U-N-S Number, a business ID issued by Dun & Bradstreet (D&B). Apple says to allow up to 5 business days to get one, plus up to 2 for Apple to receive it. Start that the week you decide to build a companion app.

If your checklist still has blanks, send your idea in three sentences to CortexTech through cortextech.dev. We build works-like IoT prototypes and will reply with the blank we would test first.

Ownership: IP, source code, schematics, and accounts

Ownership covers the code, the design files, and the online accounts the product depends on. Settle it in the contract before work starts.

United States. The US Copyright Office explains that the creator of a work is its author, unless it is a "work made for hire". For outside contractors, that label covers only nine listed categories with a signed agreement, and firmware is not among them. A transfer is valid only in writing, signed by the owner (17 U.S.C. §204(a)), so the contract needs an explicit assignment clause.

European Union. The EU Software Directive gives employers the economic rights to programs their employees write (Directive 2009/24/EC, Art. 2(3)). That rule covers employees, not outside contractors. In Germany, copyright itself cannot be transferred, and the author can only grant rights of use (UrhG §29). Ask for exclusive, unlimited rights of use in that case. This is not legal advice; have a lawyer read the contract.

Design files. Ask for the editable schematic and board files, the BOM with manufacturer part numbers, and the firmware source with build instructions.

Accounts. AWS gives an account's root user complete access to everything in it, and AWS IoT devices connect through an endpoint unique to that account. Open the cloud, app store, and code-hosting accounts in your company's name, so moving devices later does not mean updating every unit's firmware.

Questions to ask an embedded engineer or agency

Use these questions on the first call. A useful answer names a number, a part, or a file.

1. "What is the riskiest part of my idea, and how would you test it first?" Expect one row and a measurable test.
2. "Which chip and radio module would you start with, and is it certified for my markets?" The answer should match your cost and market rows.
3. "Which files will I receive at handover?" Get the list in writing.
4. "Whose accounts will hold the code, cloud, and apps?" The answer should be yours.
5. "Does the contract assign copyright and design rights to my company?"
6. "Show me a device you built with a similar chip or radio." Ask what failed on it and how they found out.
7. "How will you show progress?" Expect demos measured against your success criteria.

Seems too complicated?

Hop on a call with us through cortextech.dev, and we will sort out everything your device needs together with you.

Sources

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