Yes
No
N/A
Watchy
Open-source ESP32 smartwatch with e-paper display - ideal for wearable development, clocks, and DIY wrist apps.
46 × 35.5 mm
ESP32
MCU
240MHz
clock
4MB
flash
520KB
SRAM
17· Two 12-bit, 18 Channels ADC
GPIO
BLE 4.2+ WiFi
radio
Pinout
17 pins| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 1 | TXPWM | uart | uart | |
| 2 | 3 | RXPWM | uart | uart | |
| 3 | 4 | DOWN_BTN_PINPWM | strapping | - | |
| 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
8 pins with no boot or system involvementSCKPWMMISODISPLAY_BUSYSDAPWMSCLPWMMOSIPWMBACK_BTN_PINPWMMENU_BTN_PINPWMRTC_INT_PINPWM
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 |
|---|---|---|---|
| DOWN_BTN_PIN | GPIO4 | Sampled at reset for boot config; should not be driven at boot (affects boot mode timing). | Strapping |
| SS | GPIO5 | Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot. | Strapping |
| ACC_INT_2_PIN | 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 |
| VIB_MOTOR_PIN | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| ACC_INT_1_PIN | MTMS (GPIO14) | Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| TX | U0TXD (GPIO1) | Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console. | USB |
| RX | U0RXD (GPIO3) | Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads. | USB |
| DISPLAY_RES | GPIO9 (Flash SD2) | Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO. | Flash |
| DISPLAY_DC | GPIO10 (Flash SD3) | Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO. | 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 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…
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, SCK, MISO, SDA, SCL and 4 more are free of any such role - the safest first picks. 5 of the exposed pins carry boot-time or system duties on the ESP32 (DOWN_BTN_PIN, SS, ACC_INT_2_PIN and 2 more).
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Uses a CP2104 bridge - install the CP210x driver if no port appears. Not detected? Hold BOOT while plugging in.
2
Match & flash
Set the Tools options shown, then click Upload.
3
Verify it runs
The onboard LED on GPIO18 blinks - swap the pin if your board's LED differs.
Set these in Tools · leave everything else at default
Arduino IDE 2.x — Tools Copy
Board: "ESP32 Dev Module"▸
Flash Size: "4MB (32Mb)"▸
Flash Mode: "DIO"▸
Partition Scheme: "Default 4MB with spiffs (1.2MB APP / 1.5MB SPIFFS)" (default)▸
Upload Speed: "921600"▸
▸ every other Tools option — leave at default
Board: 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
Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32 Dev Module
// blink the onboard LED
void setup() {
pinMode(18, OUTPUT);
}
void loop() {
digitalWrite(18, HIGH); delay(500);
digitalWrite(18, LOW); delay(500);
}board to selectesp32dev⧉ copy
[env:watchy]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600Find it: PlatformIO Home ▸ Boards, search
esp32dev — or type it after board =.board to selectesp32dev⧉ copy
esp32:
board: esp32dev
variant: watchy
framework:
type: esp-idf
# blink - GPIO18
output:
- platform: gpio
pin: 18
id: led_out
light:
- platform: binary
name: "LED"
output: led_outFind it: search ESPHome's board list for
esp32dev (same ids as PlatformIO).esptool doesn't pick board settings — a prebuilt .bin already has them baked in. This is just the raw flash command.
esptool.py --chip esp32 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Build details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32 · 46 × 35.5 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
17 · Two 12-bit, 18 Channels
UART · I²C · SPI
3 · 2 · 4
PWM
16 channels
Power
USB
Micro-USB
Serial
CP2104
Boot address
0x1000
Display
Screen
ePaper · 1.54" · 200x200
Driver
GDEH0154D67
Touch
No
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · QIO
Sketch · Data
1.25 MB · 320 KB
46 × 35.5 mm
The Watchy uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with QIO 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 $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 pricesWatchy
$50.00per unit, typical
Resources
Similar boards
