Watchy
Open-source ESP32 smartwatch with e-paper display - ideal for wearable development, clocks, and DIY wrist apps.
Watchy Pinout
17 pins| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 1 | TXPWM | uart | uart | |
| 2 | 3 | RXPWM | uart | uart | |
| 3 | 4 | DOWN_BTN_PINPWM | safe | - | |
| 4 | 5 | SSDISPLAY_CSPWM | strapping | spi | |
| 5 | 9 | DISPLAY_RESPWM | strapping | - | |
| 6 | 10 | DISPLAY_DCPWM | strapping | - | |
| 7 | 12 | ACC_INT_2_PINPWM | strapping | - | |
| 8 | 13 | VIB_MOTOR_PINPWM | strapping | - | |
| 9 | 14 | ACC_INT_1_PINPWM | strapping | - | |
| 10 | 18 | SCKPWM | safe | spi | |
| 11 | 19 | MISODISPLAY_BUSYPWM | safe | spi | |
| 12 | 21 | SDAPWM | safe | i2c | |
| 13 | 22 | SCLPWM | safe | i2c | |
| 14 | 23 | MOSIPWM | safe | spi | |
| 15 | 25 | BACK_BTN_PINPWM | safe | - | |
| 16 | 26 | MENU_BTN_PINPWM | safe | - | |
| 17 | 27 | RTC_INT_PINPWM | safe | - |
Start with these
9 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
6 pins · 6 things to knowTXGPIO1 Default UART0 TX pin for USB-serial programming and console. UART
Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console.
RXGPIO3 Default UART0 RX pin for USB-serial programming (console input). UART
Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads.
SSGPIO5 Bootstrapping pin; internal pull-up; VSPI CS0 (default SPI chip-select); acts as FSPIWP (flash write-protect) on internal-flash variants. Strapping
Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot.
ACC_INT_2_PINGPIO12 Bootstrapping pin; JTAG TDI; sets flash voltage (VDD_SDIO); also HSPIQ (flash data line). Strapping
Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used.
VIB_MOTOR_PINGPIO13 JTAG clock pin (TCK); also ADC2 channel 4 / Touch4 input. JTAG
Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed.
ACC_INT_1_PINGPIO14 JTAG mode select pin (TMS); also HSPI CLK and PWM-capable GPIO. JTAG
Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot.
Only if you know the tricks
2 pins · 1 thing to knowDISPLAY_RESGPIO9DISPLAY_DCGPIO10 SPI flash/PSRAM data lines SD2 and SD3 (flash HOLD and WP) Flash
Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO.
- DISPLAY_RESConnected to SPI flash/PSRAM data 2 (SD2, flash HOLD).
- DISPLAY_DCConnected to SPI flash/PSRAM data 3 (SD3, flash WP).
The Watchy pinout brings out 17 GPIO pins - every one of them usable in your project.
For peripherals, I²C is mapped to SDA on GPIO21 and SCL on GPIO22; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO1 and GPIO3 cover serial logging and flashing.
If you want zero surprises, DOWN_BTN_PIN, SCK, MISO, SDA and 5 more are free of any such role - the safest first picks. 6 of the exposed pins carry boot-time or system duties on the ESP32 (TX, RX, SS and 3 more).
Getting started
flash your first firmware in ~2 minutesBoard: ESP32 Dev Module Flash Size: 4MB (32Mb) Flash Mode: DIO Partition Scheme: Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS) Upload Speed: 921600
// toggle GPIO4 - wire an LED and resistor to it
void setup() {
pinMode(4, OUTPUT);
}
void loop() {
digitalWrite(4, HIGH); delay(500);
digitalWrite(4, LOW); delay(500);
}[env:watchy]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32dev - or type it after board =.esp32:
board: esp32dev
variant: esp32
framework:
type: esp-idf
# blink - GPIO4
output:
- platform: gpio
pin: 4
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32dev (same ids as PlatformIO).esptool.py --chip esp32 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x1000 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Specifications
ESP32 · 46 × 35.5 mm · vs other ESP32 chips →Dimensions
About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Expect to pay about $50.00 - above the ~$20 typical for ESP32 boards.
Only 17 GPIO are broken out, where most ESP32 boards manage about 24 - worth checking the pinout covers what you need.
Onboard you'll find an ePaper 1.54" 200x200 display, a BMA423 IMU, a PCF8563 RTC, battery charging via 1.25mm 2-pin and Menu/Back/Up/Down buttons.
- Vibration motor for haptic feedback
- 3.7V 200mAh LiPo, ~5-7 days battery life in watch mode
- v1.0 shipped with a DS3231 RTC; v1.5 and v2.0 use the PCF8563
- v3 revision moves to an ESP32-S3, USB-C, native USB-CDC and a GDEY0154D67 display
Where to buy
prices are typical street pricesResources
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