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Adafruit ESP32 Feather
Feather-format ESP32 board with LiPo charging - great for wireless projects using CircuitPython or Arduino.
51 × 22.7 mm
ESP32
MCU
240MHz
clock
4MB
flash
520KB
SRAM
21· 14 ADC
GPIO
BLE 4.2+ WiFi
radio
Pinout
21 pins · 2.54 mm pitch| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 4 | A5T0PWM | strapping | adc · touch | |
| 2 | 5 | SCKPWM | strapping | spi | |
| 3 | 12 | A11T5PWM | strapping | adc · touch | |
| 4 | 13 | LED_BUILTINA12T4PWM | strapping | adc · touch | |
| 5 | 14 | A6T6PWM | strapping | adc · touch | |
| 6 | 15 | A8T3PWM | strapping | adc · touch | |
| 7 | 16 | RXPWM | strapping | uart | |
| 8 | 17 | TXPWM | strapping | uart | |
| 9 | 18 | MOSIPWM | safe | spi | |
| 10 | 19 | MISOPWM | safe | spi | |
| 11 | 22 | SCLPWM | safe | i2c | |
| 12 | 23 | SDAPWM | safe | i2c | |
| 13 | 25 | A1DAC1PWM | safe | adc · dac | |
| 14 | 26 | A0DAC2PWM | safe | adc · dac | |
| 15 | 27 | A10T7PWM | safe | adc · touch | |
| 16 | 32 | A7T9PWM | safe | adc · touch | |
| 17 | 33 | SSA9T8PWM | safe | adc · touch · spi | |
| 18 | 34 | A2 | strapping | adc | |
| 19 | 35 | BATT_MONITORA13 | strapping | adc | |
| 20 | 36 | A4 | strapping | adc | |
| 21 | 39 | A3 | strapping | adc |
Start with these
9 pins with no boot or system involvementMOSIPWMMISOPWMSCLPWMSDAPWMA1DAC1A0DAC2A10T7A7T9SSA9
Freely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| A5 | GPIO4 | Sampled at reset for boot config; should not be driven at boot (affects boot mode timing). | Strapping |
| SCK | GPIO5 | Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot. | Strapping |
| A11 | MTDI (GPIO12) | Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used. | Strapping |
| LED_BUILTIN | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| A6 | MTMS (GPIO14) | Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot. | Other |
| A8 | MTDO (GPIO15) | Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change. | Strapping |
| A2 | GPIO34 | Cannot be used as output (no drive capability); only suitable for analog/digital input. | Other |
| BATT_MONITOR | GPIO35 | Cannot be used as output; only suitable for input. | Other |
| A4 | GPIO36 (SENSOR_VP) | Cannot be used as output; only suitable for input (e.g., analog read). | Other |
| A3 | GPIO39 (SENSOR_VN) | Cannot be used as output; only suitable for input. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| RX | GPIO16 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
| TX | GPIO17 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.
Pinout notes The Adafruit ESP32 Feather pinout brings out 21 GPIO pins at a 2.54 mm pitch - every one of them usable in your project. For peripherals, I²C is mapped to SDA…
The Adafruit ESP32 Feather pinout brings out 21 GPIO pins at a 2.54 mm pitch - every one of them usable in your project.
For peripherals, I²C is mapped to SDA on GPIO23 and SCL on GPIO22; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO17 and GPIO16 cover serial logging and flashing.
On the analog side there are 14 ADC-capable pins for sensors and battery monitoring, 8 capacitive-touch inputs and 2 true DAC outputs.
If you want zero surprises, MOSI, MISO, SCL, SDA and 5 more are free of any such role - the safest first picks. 10 of the exposed pins carry boot-time or system duties on the ESP32 (A5, SCK, A11 and 7 more).
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Serial chip: CP2104. Not detected? Hold BOOT while plugging in.
2
Flash with your tool
Arduino IDE, PlatformIO, ESPHome or esptool - copy the settings on the right.
3
Verify it runs
The blink example uses GPIO18 - swap for your board's LED pin if different.
Board: Feather Esp32
Flash Size: 4MB · DIO
Upload Speed: 921600
// blink
pinMode(18, OUTPUT);
digitalWrite(18, LOW); // on (often inverted)[env:featheresp32]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32dev
variant: feather_esp32
framework:
type: esp-idf
# blink - GPIO18
output:
- platform: gpio
pin: 18
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binBuild details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32 · 51 × 22.7 mmCompute
MCU
ESP32
Clock
240 MHz
SRAM · Flash
520 KB · 4MB
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
4.2 LE
Antenna
PCB
I/O
GPIO · ADC
21 · 14
UART · I²C · SPI
3 · 2 · 4
PWM
16 channels
Power
USB
Micro-USB
Serial
CP2104
Boot address
0x1000
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · DIO
Sketch · Data
1.25 MB · 320 KB
51 × 22.7 mm · pin pitch 2.54 mm
The Adafruit ESP32 Feather uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with DIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.
About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Expect to pay about $19.95 - in line with other ESP32 boards.
Onboard you'll find battery charging (MCP73831) via JST-PH 2.0, status LEDs (Red (GPIO13), Charge) and Reset buttons.
- Battery voltage readable on A13 (GPIO35) via onboard 2:1 divider
- Automatic bootloader reset - no BOOT button hold needed to flash
Where to buy
prices are typical street pricesAdafruit ESP32 Feather
$19.95per unit, typical
Resources
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