Hardware Io

Zephyr Hardware I/O

Interface with the physical world using Zephyr's standardized driver models and hardware abstraction layers.

Core Workflows

1. Sensor Subsystem

Interact with various sensors using a uniform API for data fetching and decoding.

• Reference: sensors.md
• Key Tools: sensor_sample_fetch, sensor_channel_get, struct sensor_value.

2. Pinctrl & GPIO

Manage pin multiplexing, electrical configuration, and basic digital input/output.

• Reference: pinctrl_gpio.md
• Key Tools: pinctrl, gpio_dt_spec, GPIO_DT_SPEC_GET.

3. SoC Configuration

Tune chip-level parameters and manage hardware across multiple board variants.

• Reference: soc_config.md
• Key Tools: Kconfig, soc_common.dtsi, SoC-level overlays.

Quick Start (Sensor Polling)

#include <zephyr/drivers/sensor.h>

const struct device *temp_sensor = DEVICE_DT_GET(DT_ALIAS(ambient_temp0));
struct sensor_value val;

void poll_sensor(void) {
    if (sensor_sample_fetch(temp_sensor) == 0) {
        sensor_channel_get(temp_sensor, SENSOR_CHAN_AMBIENT_TEMP, &val);
    }
}

Professional Patterns (Hardware Engineering)

• Safe GPIO: Always use gpio_dt_spec to ensure polarity and pin number are automatically handled by the driver.
• Background Sampling: Never poll sensors in high-priority threads; use a background work queue. See kernel-services for work-queue patterns.
• Deferred Pinctrl: Define pin states in a shared .dtsi to simplify multi-revision hardware support.

Automation Tools

• gpio_alias_check.py: Detect duplicate alias entries across DTS/overlay files.

Examples & Templates

• sensor_poll_template.c: Starter polling function with readiness/error checks.

Validation Checklist

• Sensor device nodes resolve correctly and DEVICE_DT_GET(...) targets are ready at runtime.
• GPIO and pinctrl states match the intended board schematic and polarity rules.
• Sensor sampling path returns stable values with expected units/scaling.
• Background acquisition does not block high-priority or interrupt-critical code paths.

Resources

• References:
  • sensors.md: Reading data, channels, and triggers.
  • pinctrl_gpio.md: Pin multiplexing and GPIO specs.
  • soc_config.md: Multi-variant SoC configuration.
• Scripts:
  • gpio_alias_check.py: Alias duplication checker for DTS/overlay sets.
• Assets:
  • sensor_poll_template.c: Polling loop starter template.

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