ESP32-S3 Pin Function Overview
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Clarifying tool usage.
Assessing I2C requirements.
Gathering I2C pin information.
Formulating queries for I2C information.
Looking for "I2C pins supported, which GPIO can be used for I2C, IO matrix mapping, any restrictions" in esp32_s3_wroom_1_wroom_1u_datasheet_en-2930317.pdf
Looking for "Pin definitions table mentioning functions like I2C_SCL, I2C_SDA, or general statement about mapping I2C to GPIO" in esp32_s3_wroom_1_wroom_1u_datasheet_en-2930317.pdf
Looking for "Strapping pins and notes that affect I2C pin choice" in esp32_s3_wroom_1_wroom_1u_datasheet_en-2930317.pdf
Looking for "Electrical characteristics or pad capabilities related to input/output for GPIOs used with I2C" in esp32_s3_wroom_1_wroom_1u_datasheet_en-2930317.pdf
Looking for "Number of I2C controllers (I2C0/I2C1) and signal matrix routing description" in esp32_s3_wroom_1_wroom_1u_datasheet_en-2930317.pdf
Looking for "Default UART0 pins and other fixed-function pins that may conflict (e.g., USB, JTAG)" in esp32_s3_wroom_1_wroom_1u_datasheet_en-2930317.pdf
Preparing minimal response.
Here’s how I2C works on the ESP32‑S3 module and what you can use for SDA/SCL.
What the datasheet says
- Device: ESP32-S3-WROOM-1-N16R8
- I2C controllers: The ESP32‑S3 has two I2C bus interfaces (I2C0 and I2C1).
- Pin assignment: “For I2C, the pins used can be chosen from any GPIOs via the GPIO Matrix.”
- I2C speed: “Up to 800 kbit/s (constrained by SCL and SDA pull-up strength).”
- Strapping pins (affect boot): GPIO0 (weak pull-up), GPIO3 (floating), GPIO45 (weak pull-down), GPIO46 (weak pull-down). They can be used as normal GPIOs after reset, but avoid external circuits that fight their required levels at boot.
- Variant caveats:
- On modules with Octal SPI PSRAM, IO35/IO36/IO37 are not available for other uses.
- On some 1.8 V VDD_SPI variants, GPIO47/48 operate at 1.8 V.
Which GPIOs support I2C (SDA/SCL)?
- Any available GPIO on the module can be assigned as SDA or SCL via the GPIO Matrix, with the practical cautions below.
- Avoid choosing pins that conflict with other active functions in your design:
- USB Serial/JTAG or USB OTG uses GPIO19/GPIO20 when the internal PHY is enabled.
- JTAG defaults are on GPIO39–GPIO42.
- UART0 defaults to GPIO43/GPIO44 (TXD0/RXD0).
- The four strapping pins (GPIO0, GPIO3, GPIO45, GPIO46) must not be forced to the wrong level during boot.
Your chosen pins (valid)
- SDA = GPIO8
- SCL = GPIO18 These are fully supported for I2C via the GPIO Matrix and are good choices given your other peripherals.
Required pull-ups
- I2C requires external pull-up resistors on both SDA and SCL to 3.3 V. Using 4.7 kΩ is a solid starting value at 3.3 V for standard/fast mode. Example part: 4.7k Resistor.
Quick checklist for reliable I2C on this board
- Place the pull-ups close to the touch controller and keep SDA/SCL short and away from the 80 MHz SPI.
- Do not load or strap GPIO3/0/45/46 in ways that alter boot.
- If you enable on-chip USB, avoid using GPIO19/20 for I2C.
- If your module variant uses Octal PSRAM, do not plan on IO35–IO37 for I2C.
If you want, I can annotate the schematic nets so SDA=GPIO8 and SCL=GPIO18 are clearly labeled and ensure the 4.7 kΩ pull-ups to 3V3 are present.
Review my chosen pins
Pick safe default pins
Add pull-ups selection
Confirm module variant limits
25 days
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Reviews
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ESP32-S3 DevKit with 3.5" 320×480 ST7796S SPI TFT, FT6336U Capacitive Touch, Shared 80 MHz SPI, I2C Touch Bus, USB-C Power, and MicroSD Support
Pricing & Availability
Distributor | Qty 1 |
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Assets
ESP32-S3-WROOM-1-N16R8.stp
3D_ESP32-S3-WROOM-1-N16R83D Model
ESP32-S3-WROOM-1-N16R8
ESP32-S3-WROOM-1-N16R8 Symbol.svgDefault
ESP32-S3-WROOM-1-N16R8-thumb.png
ESP32-S3-WROOM-1-N16R8-thumbThumbnailkicad_mod
ESP32S3WROOM1N16R8.kicad_mod
FP_ESP32S3WROOM1N16R8FootprintControls
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