ESP Hardware Abstraction Layer for Touch Sensor Peripheral

[!NOTE] This component is currently in beta. Its API, behavior, and compatibility may change at any time and without notice; backward compatibility is not guaranteed. Use caution when integrating into production systems.

Overview

The esp_hal_touch_sens component provides a Hardware Abstraction Layer for Touch Sensor controller supported targets. Touch sensors detect touch events by measuring changes in capacitance when a finger or object approaches the touch pad, enabling capacitive touch interfaces for user interaction.

Architecture

The Touch Sensor HAL is structured in two main sub-layers:

1. HAL Layer (Upper): Defines the operational steps and data structures required to control touch sensor peripherals (e.g., initialization, channel configuration, filter setup, measurement control).

2. Low-Level Layer (Bottom): Serves as a translation layer between the HAL and the register files defined in the soc component, handling target-specific register configurations.

Supported Touch Sensor Controllers

This HAL supports various touch sensor controller versions depending on the ESP chip:

• Touch Sensor Version 1: Basic touch sensor functionality (ESP32)
• Touch Sensor Version 2: Enhanced features including improved filtering and denoise capabilities (ESP32-S2, ESP32-S3)
• Touch Sensor Version 3: Advanced features with frequency hopping, multiple sample configurations, and enhanced waterproof support (ESP32-P4 and newer chips)

Features

• Channel Management: Multi-channel touch pad support with independent configuration
• Measurement Control: Configurable charge/discharge cycles, voltage thresholds, and measurement intervals
• Filtering and Signal Processing:
  • Benchmark filter (IIR filter, jitter filter)
  • Smooth data filter for noise reduction
  • Debounce and noise threshold configuration
  • Active threshold hysteresis
• Denoise Function: Internal denoise channel (T0) to filter out power supply noise and external EMI
• Waterproof Support: Guard pad and shield channel configuration for water-resistant applications
• Proximity Sensing: Up to three touch channels can be configured as proximity sensors
• Sleep Channel: Deep sleep wake-up support with configurable sleep channel
• FSM Operation: Hardware timer or software-triggered measurement modes
• Interrupt Handling: Multiple interrupt types (active, inactive, done, scan done, timeout, proximity done)
• Sample Configuration: Multiple sample configurations with frequency hopping support (Version 3)

Usage

The HAL functions primarily serve ESP-IDF peripheral drivers such as esp_driver_touch_sens.

Advanced developers can use these interfaces directly when implementing custom drivers, with the understanding that API stability is not guaranteed.

Dependencies

• soc: Provides chip-specific register definitions
• hal: Core hardware abstraction utilities and macros