ESP32-C3 OLED 0.42" Display
ESP32-C3 development board with integrated 0.42" OLED display and RISC-V processor for compact IoT projects.
ESP32-C3 OLED 0.42" Display Pinout
16 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | 5VVUSB | power | - | USB VBUS (JP2 pin 1, square pad), taken before the 1N5819 Schottky that feeds the ME6211 3.3V regulator; a 5V input here also appears on the USB connector's VBUS |
| 2 | - | GND | ground | - | Ground (JP2 pin 2, silk GD) |
| 3 | - | 3V33.3V | power | - | 3.3V from the on-board ME6211 LDO (JP2 pin 3, silk V3) |
| 4 | 20 | IO20RX | uart | uart · pwm | UART0 RXD (U0RXD), silk RX |
| 5 | 21 | IO21TX | uart | uart · pwm | UART0 TXD (U0TXD), silk TX |
| 6 | 2 | IO2A2 | strapping | adc · pwm | ADC1_CH2, PWM |
| 7 | 1 | IO1A1 | safe | adc · pwm | ADC1_CH1, PWM |
| 8 | 0 | IO0A0 | safe | adc · pwm | ADC1_CH0, PWM |
| 9 | 10 | IO10 | safe | pwm | General-purpose GPIO (JP1 pin 1, square pad) |
| 10 | 9 | IO9SCL | strapping | i2c · pwm | Wired to the BOOT button (pressed = LOW, 10K pull-up); Arduino default I2C SCL - the on-board OLED is NOT on this pin |
| 11 | 8 | IO8SDA | strapping | i2c · pwm | Blue LED to 3.3V through 4.7K, lit when driven LOW (10K pull-up); Arduino default I2C SDA - the on-board OLED is NOT on this pin |
| 12 | 7 | IO7SS | strapping | spi · pwm | SPI SS (Arduino default), PWM |
| 13 | 6 | IO6MOSI | strapping | i2c · spi · pwm | On-board OLED I2C SCL (SSD1306-compatible), 4.7K pull-up to 3.3V; more I2C devices can share the bus. Arduino default SPI MOSI |
| 14 | 5 | IO5A5MISO | strapping | adc · i2c · spi · pwm | On-board OLED I2C SDA, 4.7K pull-up to 3.3V; more I2C devices can share the bus. ADC2_CH0 (ADC2 is not usable alongside Wi-Fi on the C3). Arduino default SPI MISO |
| 15 | 4 | IO4A4SCK | strapping | adc · spi · pwm | ADC1_CH4, SPI SCK (Arduino default), PWM |
| 16 | 3 | IO3A3 | safe | adc · pwm | ADC1_CH3, PWM |
Start with these
4 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
9 pins · 9 things to knowIO20 UART0 RXD (default serial input) UART
Used as UART0 receive (console/bootloader); repurposing may disable serial programming and debug logs
IO21 UART0 TXD (default serial output) UART
Used as UART0 transmit (console/bootloader); repurposing may disable serial console output and printing
IO2 Strapping pin, but it does not select the boot mode - GPIO9 does. Espressif only recommend pulling it up against reset-time glitches. Floating by default. Strapping
A strapping pin: Espressif recommend an external pull-up against glitches at reset, so avoid heavy capacitive loads or a strong low drive here. It does not put the chip into download mode (that is GPIO9).
IO9 Bootstrapping pin; selects boot mode (HIGH = SPI flash boot, LOW = UART download) Strapping
Controls boot mode on reset (HIGH for normal flash boot, LOW enters serial download mode)
IO8 Bootstrapping pin (needs HIGH at reset); also gates ROM boot message printing (UART_PRINT_CONTROL efuse) Strapping
Must be held high during reset (if low, UART flashing/boot may not work)
IO7 Bootstrapping pin; JTAG TDO; Flash data (FSPID in internal-flash models) JTAG
Used during boot; JTAG TDO for debugging; acts as Quad-SPI flash IO (data line) in internal-flash variants
IO6 On-board OLED I2C SCL (SSD1306-compatible), 4.7K pull-up to 3.3V; more I2C devices can share the bus. Arduino default SPI MOSI onboard hardware
Wired to the on-board 0.42 inch OLED (I2C SCL, 4.7K pull-up) on this board. The pin is yours if you give that up, but nothing else can share it.
IO5 On-board OLED I2C SDA, 4.7K pull-up to 3.3V; more I2C devices can share the bus. ADC2_CH0 (ADC2 is not usable alongside Wi-Fi on the C3). Arduino default SPI MISO onboard hardware
Wired to the on-board 0.42 inch OLED (I2C SDA, 4.7K pull-up) on this board. The pin is yours if you give that up, but nothing else can share it.
IO4 Bootstrapping pin; JTAG TMS; Flash data (FSPIHD in internal-flash models) JTAG
Used during boot; JTAG TMS for debugging; acts as Quad-SPI flash IO (hold data line) in internal-flash variants
The ESP32-C3 OLED 0.42" Display breaks out 16 pins in total: 13 GPIO for your project, with 5V, GND and 3V3 handling power.
For peripherals, 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 GPIO21 and GPIO20 cover serial logging and flashing.
On the analog side there are 6 ADC-capable pins for sensors and battery monitoring and PWM on every GPIO.
If you want zero surprises, IO1, IO0, IO10 and IO3 are free of any such role - the safest first picks. 9 of the exposed pins carry boot-time or system duties on the ESP32-C3 (IO20, IO21, IO2 and 6 more).
Getting started
flash your first firmware in ~2 minutesBoard: ESP32C3 Dev Module Flash Size: 4MB (32Mb) Flash Mode: QIO Partition Scheme: Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS) 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:esp32-c3-oled-042]
platform = espressif32
board = esp32-c3-devkitm-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32-c3-devkitm-1 - or type it after board =.esp32:
board: esp32-c3-devkitm-1
variant: esp32c3
framework:
type: esp-idf
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32-c3-devkitm-1 (same ids as PlatformIO).esptool.py --chip esp32c3 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Good to know
board-specific quirks worth 60 seconds
ESP32-C3 OLED 0.42" Features Built-in Display 0.42" OLED Screen: 72x40 resolution with high contrast I2C Interface: Connected to GPIO 8 (SDA) and GPIO 9 (SCL) Driver: SSD1306 controller for easy integration Technical Specifications Based on ESP32-C3 RISC-V processor with 13 GPIO pins. Perfect for projects requiring visual feedback in ultra-compact form factors. Perfect For Ideal for wearable devices, smart…
ESP32-C3 OLED 0.42" Features
Built-in Display
- 0.42" OLED Screen: 72x40 resolution with high contrast
- I2C Interface: Connected to GPIO 8 (SDA) and GPIO 9 (SCL)
- Driver: SSD1306 controller for easy integration
Technical Specifications
Based on ESP32-C3 RISC-V processor with 13 GPIO pins. Perfect for projects requiring visual feedback in ultra-compact form factors.
Perfect For
Ideal for wearable devices, smart sensors, mini IoT projects, and applications where a tiny display is essential without external components.
Downloads
Free for non-commercial use, credit espboards.dev · License
Board illustration
The bare ESP32-C3 OLED 0.42" Display board drawn to scale at 25 × 20.5 mm, with no pin labels on it. Made for slide decks, wiring diagrams and project write-ups where a photo is too busy. Take the scalable SVG for print or editing, the high-resolution PNG to drop straight in, or the transparent PNG when you need it with no background behind it.
Pinout diagram
Every pin on both sides of the board with its functions, drawn by ESPboards from the ESP32-C3 Series Datasheet v2.4 - the same sheet shown at the top of this page. The PNG is a high-resolution image for screens, the SVG is vector so it stays sharp at any size, and the PDF is laid out to print on A4 or Letter.
Yours to use, share and adapt for non-commercial work, as long as you credit espboards.dev - the full terms and ready-made credit lines are here.
Specifications
ESP32-C3 · 25 × 20.5 mm · vs other ESP32 chips →Dimensions
About this board
At its core is the ESP32-C3 - a single-core RISC-V and the budget low-power pick.
Expect to pay about $8.99 - in line with other ESP32-C3 boards.
Onboard you'll find an OLED 0.42" 72x40 display and Reset/Boot buttons.
The ESP32-C3 OLED 0.42" is a compact development board featuring the ESP32-C3 RISC-V microcontroller with integrated Wi-Fi 802.11 b/g/n and Bluetooth 5 (LE) connectivity.
Powered by a 32-bit RISC-V single-core processor running at up to 160 MHz, with 4MB flash memory and 400KB SRAM, it's perfect for IoT applications and embedded projects.
The board features a built-in 0.42" OLED display with 72x40 resolution connected via I2C, ideal for displaying sensor data, status information, or user interfaces. It offers 13 GPIO pins with support for ADC (6 channels, 12-bit), PWM, and various communication interfaces including UART, SPI, I2C, and I2S.
Operating at 3.3V with Micro-USB interface for programming and power. Ultra-compact design makes it suitable for wearable and space-constrained applications.
- OLED Screen
Where to buy
prices are typical street pricesResources
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