Day34 Log - IIO I2C Driver Implementation

Summary

Implemented a multi-channel IIO driver over I2C for a custom STM32-based sensor.

Key achievements:

• Successful I2C communication with fake sensor
• IIO device registration
• Multi-channel sysfs interface
• Dynamic data updates observed

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Issues Encountered

1. Static values (no update)

Cause:

• sensor_task_process() not called in main loop

Fix:

• Move sensor execution to main loop

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2. Module reload failure

insmod: Cannot allocate memory

Cause:

• Attempted reload in invalid context / device state

Fix:

• Ensure module removed
• verify I2C device ready
• reinsert module

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3. Overlay warnings

memory leak will occur if overlay removed

Cause:

• modifying bus node properties in overlay

Impact:

• No functional issue for current use

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Observations

1. Channel mapping works

ADC0 → in_voltage0_raw
ADC1 → in_voltage1_raw
ADC2 → in_voltage2_raw

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2. Data pattern verified

Observed:

1229 / 1329 / 1429
1302 / 1402 / 1502

Confirms:

• deterministic sample update
• correct channel offset
• correct register mapping

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3. End-to-end pipeline validated

STM32 → I2C → IIO → sysfs

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Key Learning

• IIO integrates cleanly with I2C drivers
• Channel metadata drives user-space interface
• Time-driven sensor design is critical
• Multi-channel support is natural in IIO

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Reflection

This implementation bridges:

• MCU firmware design
• Linux driver development
• IIO framework usage

It provides a complete vertical integration example.

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Next Step

Day35:

• Add data-ready GPIO (DRDY)
• Introduce interrupt handling
• Prepare for IIO buffer/trigger

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