OLIMEX ESP32-EVB
ESP32 board with relays and Ethernet - built for industrial control and automation systems.
OLIMEX ESP32-EVB Pinout
11 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 1 | TXPWM | uart | uart | |
| 2 | 2 | MOSIPWM | strapping | spi | |
| 3 | 3 | RXPWM | uart | uart | |
| 4 | 4 | TX1PWM | safe | - | |
| 5 | 13 | SDAPWM | strapping | i2c | |
| 6 | 14 | SCKPWM | strapping | spi | |
| 7 | 15 | MISOPWM | strapping | spi | |
| 8 | 16 | SCLPWM | safe | i2c | |
| 9 | 17 | SSPWM | safe | spi | |
| 10 | 34 | KEY_BUILTIN | strapping | - | |
| 11 | 36 | RX1 | strapping | - |
Start with these
3 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
8 pins · 8 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.
MOSIGPIO2 Bootstrapping pin (must be low or floating at reset); internal pull-down. Strapping
If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure.
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.
SDAGPIO13 JTAG clock pin (TCK); also ADC2 channel 4 / Touch4 input. JTAG
Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed.
SCKGPIO14 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.
MISOGPIO15 Bootstrapping pin; JTAG TDO; controls UART0 boot log output; also HSPICS0 (secondary SPI CS). Strapping
Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change.
KEY_BUILTINGPIO34 Input-only GPIO (no output driver); ADC1 channel 6. Other
Cannot be used as output (no drive capability); only suitable for analog/digital input.
RX1GPIO36 Input-only GPIO (no output); ADC1 channel 0, Hall sensor VP. Other
Cannot be used as output; only suitable for input (e.g., analog read).
All 11 pins on the OLIMEX ESP32-EVB are usable GPIO, spaced at the standard 2.54 mm pitch.
Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO13 and SCL on GPIO16; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO1 and GPIO3 cover serial logging and flashing.
8 of the exposed pins carry boot-time or system duties on the ESP32 (TX, MOSI, RX and 5 more) - check the guidance above before wiring anything to them. TX1, SCL and SS are free of any such role - the safest first picks.
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:esp32-evb]
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 · 75 × 75 mm · vs other ESP32 chips →Dimensions
About this board
Inside sits the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
At $23.23 it's on the expensive side for an ESP32 board - most land around $20.
Only 11 GPIO are broken out, where most ESP32 boards manage about 24 - worth checking the pinout covers what you need.
Around the module: a microSD slot, an IR transceiver, a CAN bus interface (MCP2562-E), 2 relays, wired Ethernet (LAN8710A), battery charging (BL4054B) and Reset/User buttons.
- UEXT connector for Olimex sensors/modules
- External u.FL antenna on -EA variants (ESP32-WROOM-32UE)
- Industrial temperature variants (-40 to +85°C)
- Battery-only mode disables relays, CAN and USB (no step-up converter)
Where to buy
prices are typical street pricesResources
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