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esp32

ESP32硬件平台规格，包括GPIO引脚、PWM功能、ADC/DAC、通信接口以及硬件限制。在为ESP32生成代码或验证引脚配置时，请参考这些规格。

SKILL.md
--- frontmatter
name: esp32
description: ESP32 hardware platform specifications including GPIO pins, PWM capabilities, ADC/DAC, communication interfaces, and hardware constraints. Reference this when generating code for ESP32 or validating pin configurations.
user-invocable: false

ESP32 DevKit V1 Hardware Platform

Core Specifications

  • •MCU: ESP32-WROOM-32 (Dual-core Xtensa LX6)
  • •Operating Voltage: 3.3V (⚠️ NOT 5V tolerant)
  • •Clock Speed: 240 MHz (dual-core, adjustable)
  • •Flash Memory: 4 MB
  • •SRAM: 520 KB
  • •ROM: 448 KB
  • •Built-in Peripherals: WiFi 802.11 b/g/n, Bluetooth v4.2 BR/EDR and BLE

GPIO Pin Capabilities

Digital GPIO Pins

Available: GPIO 0-39 (40 pins total)

Usable for general I/O: 0-5, 12-19, 21-23, 25-27, 32-39

PWM-Capable Pins

All GPIO pins support PWM via LEDC peripheral (16 independent channels, 0-15)

  • •Frequency range: 1 Hz to 40 MHz
  • •Resolution: 1-16 bits (configurable)
  • •Recommended for PWM: 16, 17, 18, 19, 21, 22, 23, 25, 26, 27

Analog Input (ADC)

ADC1 (usable with WiFi): GPIO 32, 33, 34, 35, 36, 39

  • •12-bit resolution (0-4095)
  • •0-3.3V input range
  • •Attenuation configurable (0dB, 2.5dB, 6dB, 11dB)

ADC2 (CANNOT use when WiFi active): GPIO 0, 2, 4, 12, 13, 14, 15, 25, 26, 27

  • •Same specs as ADC1
  • •⚠️ Critical: ADC2 is disabled when WiFi is running

Analog Output (DAC)

DAC Pins: GPIO 25, GPIO 26

  • •8-bit resolution (0-255)
  • •0-3.3V output range
  • •Use dacWrite(pin, value)

Interrupt-Capable Pins

All GPIO pins support interrupts

  • •Rising edge, falling edge, both edges, low level, high level
  • •Use attachInterrupt(digitalPinToInterrupt(pin), ISR, mode)

Communication Interfaces

UART (Serial)

UART0: RX=GPIO3, TX=GPIO1 (connected to USB)

  • •Default for Serial.println()
  • •Used by bootloader

UART1: RX=GPIO9, TX=GPIO10

  • •⚠️ Connected to flash memory, not recommended for general use

UART2: RX=GPIO16, TX=GPIO17

  • •Recommended for external serial devices
  • •Can be remapped to other pins

I2C (Wire)

Default pins: SDA=GPIO21, SCL=GPIO22

  • •Can be remapped to any GPIO pair
  • •Master or slave mode
  • •Standard (100 kHz) and Fast (400 kHz) modes

SPI

VSPI (default):

  • •MOSI=GPIO23
  • •MISO=GPIO19
  • •SCK=GPIO18
  • •SS=GPIO5

HSPI:

  • •MOSI=GPIO13
  • •MISO=GPIO12
  • •SCK=GPIO14
  • •SS=GPIO15

Both can be remapped to other pins.

Pin Constraints and Special Functions

⚠️ Input-Only Pins

GPIO 34, 35, 36, 39 are INPUT ONLY

  • •No internal pull-up/pull-down resistors
  • •Cannot be used with pinMode(pin, OUTPUT)
  • •Cannot be used with pinMode(pin, INPUT_PULLUP)

⚠️ Strapping Pins (Boot Mode)

These pins affect boot mode and should be avoided for critical functions:

GPIO 0:

  • •Must be HIGH during boot
  • •Has internal pull-up
  • •Boot button usually connected here
  • •Safe to use after boot

GPIO 2:

  • •Must be LOW or floating during boot
  • •Has internal pull-down
  • •Some boards have built-in LED here

GPIO 5:

  • •Controls SDIO slave timing
  • •Has internal pull-up

GPIO 12:

  • •Controls flash voltage (VDD_SDIO)
  • •Must be LOW during boot for 3.3V flash
  • •Has internal pull-down

GPIO 15:

  • •Must be HIGH during boot
  • •Controls boot message output
  • •Has internal pull-up

Touch Sensing

Touch-capable pins: GPIO 0, 2, 4, 12, 13, 14, 15, 27, 32, 33

  • •Use touchRead(pin) to get capacitance value
  • •Threshold-based touch detection

RTC GPIO (Deep Sleep Wake)

RTC_GPIO pins: 0, 2, 4, 12-15, 25-27, 32-39

  • •Can wake ESP32 from deep sleep
  • •Retain state during deep sleep

Pin Selection Best Practices

For Digital Output (LED, Relay, etc.)

Best choices: 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 32, 33 Avoid: Strapping pins (0, 2, 5, 12, 15), input-only pins (34-39)

For Digital Input (Button, Sensor)

Best choices: 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 32, 33, 34, 35, 36, 39 Avoid: Strapping pins if possible

For PWM (Servo, Motor, LED dimming)

Best choices: 16, 17, 18, 19, 21, 22, 23, 25, 26, 27 Avoid: Strapping pins, input-only pins

For Analog Input (Sensors)

Best choices: 32, 33, 34, 35, 36, 39 (ADC1 - works with WiFi) Avoid: ADC2 pins if using WiFi (0, 2, 4, 12-15, 25-27)

For I2C

Default: SDA=21, SCL=22 (recommended to keep default) Alternative: Any GPIO pair except input-only pins

For SPI

Recommended: Use default VSPI pins (23, 19, 18, 5) Alternative: HSPI or custom pins

Power and Current

  • •Max current per GPIO: 40 mA (recommended 20 mA)
  • •Max total current: 200 mA across all pins
  • •Operating voltage: 3.3V logic level
  • •⚠️ Never connect 5V signals directly - use level shifters

Pin Conflict Checker

Before assigning a pin, verify:

  1. •✅ Pin supports required function (INPUT/OUTPUT/PWM/ADC/etc.)
  2. •✅ Not an input-only pin if output needed (avoid 34, 35, 36, 39)
  3. •✅ Not a strapping pin if possible (avoid 0, 2, 5, 12, 15)
  4. •✅ Not already used by another peripheral in your project
  5. •✅ If using WiFi, avoid ADC2 pins for analog input

Common Pin Assignments

Safe General Purpose Pins

These are the safest pins for most projects:

  • •GPIO 16, 17: Often free, good for general I/O
  • •GPIO 21, 22: I2C default but can be repurposed
  • •GPIO 23: VSPI MOSI but can be repurposed
  • •GPIO 25, 26: Have DAC if needed
  • •GPIO 32, 33: Good for analog or digital

Pins to Avoid

  • •GPIO 6-11: Connected to flash memory (SPI flash)
  • •GPIO 34-39: Input only
  • •GPIO 1, 3: UART0 (USB serial)

Hardware Errata

  • •ADC readings can be affected by WiFi activity (use ADC1)
  • •Some boards have LED on GPIO 2 that can interfere
  • •Touch sensor values vary with board design
  • •Deep sleep current depends on which pins are used