UM FeatherS3
A Feather-format ESP32-S3 board with 16MB Flash and 8MB PSRAM, offering USB-C connectivity and support for various peripherals.
UM FeatherS3 Pinout
22 pins · 2.54 mm pitch| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 1 | A0T1PWM | safe | adc · touch | |
| 2 | 2 | A1VBAT_SENSEPWM | safe | adc | |
| 3 | 3 | A2T3PWM | strapping | adc · touch | |
| 4 | 4 | A3PWM | safe | adc | |
| 5 | 5 | SSA4T5PWM | safe | adc · touch · spi | |
| 6 | 6 | A5T6PWM | safe | adc · touch | |
| 7 | 7 | A6T7PWM | safe | adc · touch | |
| 8 | 8 | SDAA7T8PWM | safe | adc · touch · i2c | |
| 9 | 9 | SCLA8T9PWM | strapping | adc · touch · i2c | |
| 10 | 10 | A9T10PWM | strapping | adc · touch | |
| 11 | 11 | A10T11PWM | strapping | adc · touch | |
| 12 | 12 | A11T12PWM | strapping | adc · touch | |
| 13 | 13 | A12LED_BUILTINLEDPWM | strapping | adc | |
| 14 | 14 | T14PWM | strapping | touch | |
| 15 | 34 | VBUS_SENSEPWM | safe | - | |
| 16 | 35 | MOSISDOPWM | safe | spi | |
| 17 | 36 | SCKPWM | safe | spi | |
| 18 | 37 | MISOSDIPWM | safe | spi | |
| 19 | 39 | RGB_PWRLDO2PWM | strapping | - | |
| 20 | 40 | RGB_DATAPWM | strapping | - | |
| 21 | 43 | TXPWM | uart | uart | |
| 22 | 44 | RXPWM | uart | uart |
Start with these
11 pins with no boot or system involvementFreely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
11 pins · 6 things to knowA2GPIO3 Bootstrapping pin (controls JTAG signal source) Strapping
Sampled at reset to select JTAG interface (USB Serial/JTAG controller vs. external pins). Improper use can disable external JTAG or alter debug interface.
SCLGPIO9A9GPIO10A10GPIO11A11GPIO12A12GPIO13T14GPIO14 General-purpose SPI2 (FSPI) IO MUX pins Other
IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet lists it as a priority-2 pin ("can be freely used without restrictions"), so it is only taken if your board wires flash, an SD card or a display to FSPI.
- SCLGeneral-purpose SPI2 (FSPI) IO MUX pin - hold/data line (FSPIHD)
- A9General-purpose SPI2 (FSPI) IO MUX pin - chip select (FSPICS0)
- A10General-purpose SPI2 (FSPI) IO MUX pin - data in (FSPID)
- A11General-purpose SPI2 (FSPI) IO MUX pin - clock (FSPICLK)
- A12General-purpose SPI2 (FSPI) IO MUX pin - data out (FSPIQ)
- T14General-purpose SPI2 (FSPI) IO MUX pin - write-protect/data line (FSPIWP)
RGB_PWRGPIO39 JTAG test clock (MTCK); IO MUX alternates CLK_OUT3 and SUBSPICS1 (chip select on the alternative SUBSPI memory bus, unused on standard modules) JTAG
Default JTAG TCK - keep it free if you debug over JTAG. It is not a flash or PSRAM line on standard modules: those sit on GPIO26-37.
RGB_DATAGPIO40 JTAG test data out pin (MTDO) JTAG
Default JTAG TDO output for debugging. Using it as GPIO will interfere with JTAG debugging functionality.
TXGPIO43 UART0 transmit pin (U0TXD), default serial console TX UART
Used for bootloader output and UART console logs. If repurposed, you will lose the default serial output (and programming via UART0).
RXGPIO44 UART0 receive pin (U0RXD), default serial console RX UART
Used for bootloader input (download mode via serial). If repurposed, you cannot use the default UART0 download mode for programming the chip.
All 22 pins on the UM FeatherS3 are usable GPIO, spaced at the standard 2.54 mm pitch.
Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO8 and SCL on GPIO9; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO43 and GPIO44 cover serial logging and flashing.
Beyond plain digital I/O you get 13 ADC-capable pins for sensors and battery monitoring and 11 capacitive-touch inputs.
11 of the exposed pins carry boot-time or system duties on the ESP32-S3 (A2, SCL, A9 and 8 more) - check the guidance above before wiring anything to them. A0, A1, A3, SS and 7 more are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutesBoard: ESP32S3 Dev Module USB CDC On Boot: Enabled Flash Size: 16MB (128Mb) Flash Mode: DIO PSRAM: QSPI PSRAM Partition Scheme: 16M Flash (3MB APP/9.9MB FATFS) Upload Speed: 921600
// toggle GPIO1 - wire an LED and resistor to it
void setup() {
pinMode(1, OUTPUT);
}
void loop() {
digitalWrite(1, HIGH); delay(500);
digitalWrite(1, LOW); delay(500);
}[env:feathers3]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600
board_build.arduino.memory_type = qio_qspi
build_flags = -DBOARD_HAS_PSRAMesp32-s3-devkitc-1 - or type it after board =.esp32:
board: esp32-s3-devkitc-1
variant: esp32s3
framework:
type: esp-idf
psram:
mode: quad
speed: 80MHz
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32-s3-devkitc-1 (same ids as PlatformIO).esptool.py --chip esp32s3 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Specifications
ESP32-S3 · 52.3 × 22.9 mm · vs other ESP32 chips →Dimensions
About this board
Inside sits the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.
At $22.50 it's cheaper than most ESP32-S3 boards, which usually run around $29.
Around the module: 8MB (QSPI) PSRAM, a STEMMA QT connector, an addressable RGB LED (GPIO40), an ambient-light sensor, battery charging (MCP73831) via JST-PH 2.0 and Reset/Boot buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S3 boards.
- Dual 700mA LDO regulators - second LDO (IO39) powers the RGB LED and a switchable 3V3 rail that auto-shuts down in deep sleep
- Onboard 3D high-gain antenna (a separate u.FL-connector variant is also sold)
Where to buy
prices are typical street pricesResources
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