Hornbill ESP32 Minima
Slimmed-down ESP32 board with basic I/O - great for embedding into finished products or compact devices.
Pinout
16 pins| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | A11T1 | strapping | adc · touch | |
| 2 | 1 | TXPWM | uart | uart | |
| 3 | 2 | SSA12T2PWM | strapping | adc · touch · spi | |
| 4 | 3 | RXPWM | uart | uart | |
| 5 | 4 | A10T0PWM | strapping | adc · touch | |
| 6 | 13 | A14PWM | strapping | adc | |
| 7 | 15 | A13T3PWM | strapping | adc · touch | |
| 8 | 18 | SCKPWM | safe | spi | |
| 9 | 19 | MISOPWM | safe | spi | |
| 10 | 21 | SDAPWM | safe | i2c | |
| 11 | 22 | SCLPWM | safe | i2c | |
| 12 | 23 | MOSIPWM | safe | spi | |
| 13 | 25 | DAC1PWM | safe | dac | |
| 14 | 26 | DAC2PWM | safe | dac | |
| 15 | 34 | A6 | strapping | adc | |
| 16 | 35 | A7 | strapping | adc |
Start with these
7 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
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| A11 | GPIO0 | Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode. | Strapping |
| SS | GPIO2 | If driven HIGH on reset (while IO0 is LOW), selects an unsupported SDIO boot mode, causing boot failure. | Strapping |
| A10 | GPIO4 | Sampled at reset for boot config; should not be driven at boot (affects boot mode timing). | Strapping |
| A14 | MTCK (GPIO13) | Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed. | Other |
| A13 | MTDO (GPIO15) | Keep HIGH during boot (internal PU); if LOW on reset, bootloader log is silenced and boot mode may change. | Strapping |
| A6 | GPIO34 | Cannot be used as output (no drive capability); only suitable for analog/digital input. | Other |
| A7 | GPIO35 | 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 |
Pinout notes The Hornbill ESP32 Minima pinout brings out 16 GPIO pins - every one of them usable in your project. For peripherals, I²C is mapped to SDA on GPIO21 and SCL on…
The Hornbill ESP32 Minima pinout brings out 16 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.
On the analog side there are 7 ADC-capable pins for sensors and battery monitoring, 4 capacitive-touch inputs and 2 true DAC outputs.
If you want zero surprises, SCK, MISO, SDA, SCL and 3 more are free of any such role - the safest first picks. 7 of the exposed pins carry boot-time or system duties on the ESP32 (A11, SS, A10 and 4 more).
Getting started
flash your first firmware in ~2 minutesBoard: Hornbill Esp32 Minima
Flash Size: 4MB · DIO
Upload Speed: 921600
// blink
pinMode(18, OUTPUT);
digitalWrite(18, LOW); // on (often inverted)[env:hornbill32minima]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32dev
variant: hornbill32minima
framework:
type: esp-idf
# blink - GPIO18
output:
- platform: gpio
pin: 18
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binSpecifications
ESP32About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Expect to pay about $12.00 - less than the ~$20 most ESP32 boards go for.
Only 16 GPIO are broken out, where most ESP32 boards manage about 24 - worth checking the pinout covers what you need.
Onboard you'll find battery charging via true, status LEDs (Power, RGB) and Reset buttons.
- Round wearable form factor with large crocodile-clip I/O pads
- No onboard USB - flashed via a 6-pin header with an external USB-to-serial adapter
- Onboard 32.768 kHz crystal for RTC and accurate deep-sleep timing
Where to buy
prices are typical street pricesResources
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