What the interviewer wants
- Acquisition chain from sensor to features
- Memory and CPU budget
- Power plan for a 3-year battery life
Constraints
- Accelerometer over SPI with a 32-sample FIFO; 3 axes, 16-bit, up to 6.4 kHz ODR
- Cortex-M4F at 64 MHz, 256 KB RAM, 1 MB flash, BLE radio
- Features needed up to 2 kHz; one capture of about 1 s per minute is enough
- Battery: one 3.6 V 8.5 Ah lithium thionyl chloride cell
If you ask the interviewer
- Is continuous monitoring needed? No. Measure 1 s every minute; raw capture on request only.
- What FFT resolution? About 1 Hz resolution up to 2 kHz is enough.
- Temperature range? −20 °C to +70 °C on the motor housing.
How it's graded
The rubric a senior interviewer would use. Each item is scored 0 to 3 and weighted.
| Sampling and aliasing | weight 3 |
| Acquisition pipeline | weight 3 |
| Memory and CPU budget | weight 2 |
| Power budget | weight 3 |
| Validation | weight 1 |
How to structure your answer
- Requirements and assumptions: the numbers that drive the design.
- Architecture: blocks, tasks, data flow, memory.
- Key decisions and trade-offs, with the alternatives you rejected.
- Failure modes and recovery.
- Testing and validation.
More design rounds
Write your design in five sections and get it graded against this rubric, with a follow-up question from the AI interviewer.
Answer this round