Review the evidence signals before interviewing. Then use the anchored descriptions—not instinct alone—to choose the score that best matches each answer.
01
Evaluation factor
Technical depth
35% weight
Probe bare-metal and RTOS work: C on ARM Cortex-M, FreeRTOS or Zephyr, interrupt priorities, DMA, I2C/SPI/UART drivers, low-power sleep modes, and BLE or LoRaWAN stacks.
Evidence to listen for
Explains the physics or mechanism behind their work, not just the tooling
Names the standards, tolerances, and constraints they designed against
Can defend a design decision under follow-up questions
Distinguishes what they personally engineered from what the team delivered
Five-point scoring guide
1
Poor
Cannot explain the fundamentals of their own stated specialism.
2
Needs Improvement
Knows the vocabulary but not the underlying mechanism; struggles under follow-ups.
3
Satisfactory
Solid working knowledge for the role; depth thins out on edge cases.
4
Very Good
Strong command of the domain; explains trade-offs and defends decisions well.
5
Excellent
Names specific MCUs and peripherals, explains ISR latency, clock trees and sleep current budgets without reaching for vague abstractions.
02
Evaluation factor
Work that shipped
30% weight
Ask which shipped devices carry their firmware: production volumes, bootloader and OTA update design, certification passes (FCC, CE, Bluetooth SIG), and field failure rates after release.
Evidence to listen for
Names specific programmes, parts, or systems that reached production or field use
States their own scope inside the project
Can give measured outcomes: yield, cycle time, cost, failure rate
Explains what went wrong and what they changed
Five-point scoring guide
1
Poor
No delivered work; experience is coursework, lab-only, or purely observational.
2
Needs Improvement
Contributed to projects but cannot say what shipped or what their part was.
3
Satisfactory
Has delivered real work; outcomes described without numbers.
4
Very Good
Names shipped work and their scope, with some measured results.
5
Excellent
Points to devices in production, describes their OTA and rollback scheme, and knows the post-launch defect and battery-life numbers.
03
Evaluation factor
Diagnosis under uncertainty
20% weight
Test debugging of intermittent faults: hard fault tracing with JTAG or SWD, logic analyser and oscilloscope captures, stack overflows, memory leaks, race conditions, and radio dropouts in the field.
Evidence to listen for
Describes a real failure they chased to root cause
Shows a method: isolate variables, reproduce, measure, eliminate
Distinguishes correlation from cause
Says what they ruled out and why, not only what the answer turned out to be
Five-point scoring guide
1
Poor
No diagnostic method; guesses or escalates immediately.
2
Needs Improvement
Trial and error with no structure; cannot explain how they narrowed the cause.
3
Satisfactory
Reasonable method on familiar problems; less structured on novel ones.
4
Very Good
Clear systematic approach with a real root-cause story.
5
Excellent
Walks through one nasty bug end to end, showing how instrumentation narrowed hardware, timing and software causes before the fix.
04
Evaluation factor
Working across the org
15% weight
Assess handoffs with hardware engineers on schematics and bring-up, plus work with cloud, mobile and QA teams on protocol contracts, MQTT payloads and test fixtures.
Evidence to listen for
Explains technical constraints to non-technical stakeholders without condescension
Has negotiated scope, cost, or timeline with manufacturing, product, or suppliers
Documents decisions so others can act on them
Takes review feedback without defensiveness
Five-point scoring guide
1
Poor
Cannot communicate outside their specialism; dismissive of other functions.
2
Needs Improvement
Communication gaps cause rework; avoids stakeholder contact.
3
Satisfactory
Works adequately with other teams; documentation is thin.
4
Very Good
Communicates clearly across functions; reliable collaborator.
5
Excellent
Describes reviewing schematics pre-layout, negotiating message formats with backend teams, and giving manufacturing usable test and provisioning tooling.
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