Sensor API: Design a Sensor Data Collection API for Embedded Devices

Question

## Problem

Design a C API for reading sensor data from an embedded device. The API must support registering multiple sensor types, polling or interrupt-driven data collection, and buffering readings for batch retrieval by the host application.

```c
typedef enum {
    SENSOR_TEMP,
    SENSOR_HUMIDITY,
    SENSOR_PRESSURE
} SensorType;

typedef struct {
    SensorType type;
    float value;
    uint32_t timestamp_ms;
} SensorReading;

// Register a sensor; returns handle or -1 on error
int sensor_register(SensorType type, uint32_t poll_interval_ms);

// Read buffered data since last call; returns count written
int sensor_read_batch(int handle, SensorReading* out, int max_count);

// Enable interrupt-driven mode; callback fires on new data
int sensor_set_irq(int handle, void (*callback)(SensorReading));

void sensor_deregister(int handle);
```

## Follow-ups

1. How do you make the ring buffer for readings interrupt-safe without disabling global interrupts?
2. What happens if the host is too slow to drain the buffer and it overflows? How do you signal this?
3. How would you expose this C API via a Python ctypes wrapper for testing on a host machine?
4. How do you design the timestamp to remain monotonic across CPU clock rollovers?

Sensor API: Design a Sensor Data Collection API for Embedded Devices

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