No
No
N/A
WEMOS D1 R32
Arduino Uno-compatible ESP32 board - perfect for developers transitioning from AVR to ESP.
68.6 × 53.4 mm
ESP32
MCU
240MHz
clock
4MB
flash
520KB
SRAM
22· 6 ADC
GPIO
BLE 4.2+ WiFi
radio
Pinout
22 pins · 2.54 mm pitch| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 1 | TXD1PWM | uart | uart | |
| 2 | 2 | A0LED_BUILTINPWM | strapping | adc | |
| 3 | 3 | RXD0PWM | uart | uart | |
| 4 | 4 | A1PWM | strapping | adc | |
| 5 | 5 | SSD10PWM | strapping | spi | |
| 6 | 12 | D8PWM | strapping | - | |
| 7 | 13 | D9PWM | strapping | - | |
| 8 | 14 | D7PWM | strapping | - | |
| 9 | 16 | D5PWM | strapping | - | |
| 10 | 17 | D4PWM | strapping | - | |
| 11 | 18 | SCKD13PWM | safe | spi | |
| 12 | 19 | MISOD12PWM | safe | spi | |
| 13 | 21 | SDAPWM | safe | i2c | |
| 14 | 22 | SCLPWM | safe | i2c | |
| 15 | 23 | MOSID11PWM | safe | spi | |
| 16 | 25 | D3PWM | safe | - | |
| 17 | 26 | D2PWM | safe | - | |
| 18 | 27 | D6PWM | safe | - | |
| 19 | 34 | A3 | strapping | adc | |
| 20 | 35 | A2 | strapping | adc | |
| 21 | 36 | A4 | strapping | adc | |
| 22 | 39 | A5 | strapping | adc |
Start with these
8 pins with no boot or system involvementSCKD13MISOD12SDAPWMSCLPWMMOSID11D3PWMD2PWMD6PWM
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 |
|---|---|---|---|
| A0 | GPIO2 | If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure. | Strapping |
| A1 | 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 |
| D8 | 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 |
| D9 | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| D7 | MTMS (GPIO14) | Used for JTAG debugging (TMS); driving it as GPIO may interfere with JTAG or produce spurious signals at boot. | Other |
| A3 | GPIO34 | Cannot be used as output (no drive capability); only suitable for analog/digital input. | Other |
| A2 | 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 |
| A5 | 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 |
|---|---|---|---|
| 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 |
| D5 | GPIO16 | Connected to internal PSRAM on PSRAM-enabled modules; not usable as GPIO on those modules. | Flash |
| D4 | 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 All 22 pins on the WEMOS D1 R32 are usable GPIO, spaced at the standard 2.54 mm pitch. Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO21 and…
All 22 pins on the WEMOS D1 R32 are usable GPIO, spaced at the standard 2.54 mm pitch.
Peripheral wiring is straightforward: 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.
Beyond plain digital I/O you get 6 ADC-capable pins for sensors and battery monitoring.
10 of the exposed pins carry boot-time or system duties on the ESP32 (A0, A1, SS and 7 more) - check the guidance above before wiring anything to them. SCK, MISO, SDA, SCL and 4 more are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Uses a CH340 bridge - install the CH340 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:d1_uno32]
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: d1_uno32
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 · 68.6 × 53.4 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
22 · 6
UART · I²C · SPI
3 · 2 · 4
PWM
16 channels
Power
USB
Micro-USB
Serial
CH340
Boot address
0x1000
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · DIO
Sketch · Data
1.25 MB · 320 KB
68.6 × 53.4 mm · pin pitch 2.54 mm
The WEMOS D1 R32 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
Inside sits the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Around the module: status LEDs (Power, User (GPIO2)) and Reset buttons.
Resources
Similar boards
