Writing an SPI Sensor Driver | Dataford Interview Questions

Walk through the process of writing a custom device driver for an SPI-based sensor from scratch.

Implement the core read path as a function that consumes recorded SPI transfers. Validate each four-byte frame, retry failed frames, decode the signed 16-bit sample, and apply scaling. Return None when a sample cannot be read within its retry limit.

I/O Contract

transfers is a list of [status, high_byte, low_byte, crc] frames. Return one decoded value per requested sample.

Constraints

0 <= sample_count <= 10^4
0 <= retries <= 10
Each transfer contains exactly four integers: status, high byte, low byte, and checksum
0 <= status, high byte, low byte, checksum <= 255
scale_den > 0
A valid checksum equals status XOR high byte XOR low byte
A valid sample has status 0

Function Signature

def read_sensor_samples(transfers, sample_count, retries, scale_num, scale_den):

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