INEX OpenKB
ESP32 education board in the KidBright family - with a 16x8 LED matrix, light and temperature sensors, an RTC and a buzzer for classroom coding.
INEX OpenKB Pinout
27 pins| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | A11T1 | strapping | adc · touch | |
| 2 | 1 | TXWIRE1_PIN_DEFINEDPWM | uart | uart | |
| 3 | 2 | A12T2WIFI_LEDPWM | strapping | adc · touch | |
| 4 | 3 | RXPWM | uart | uart | |
| 5 | 4 | A10T0SDA1PWM | safe | adc · touch | |
| 6 | 5 | SSSCL1PWM | strapping | spi | |
| 7 | 12 | A15T5IOT_LEDPWM | strapping | adc · touch | |
| 8 | 13 | A14T4BUZZERPWM | strapping | adc · touch | |
| 9 | 14 | A16T6SW2PWM | strapping | adc · touch | |
| 10 | 15 | A13T3NTP_LEDPWM | strapping | adc · touch | |
| 11 | 16 | LED_BUILTINSW1PWM | safe | - | |
| 12 | 17 | BT_LEDPWM | safe | - | |
| 13 | 18 | SCKKB_GPIO18PWM | safe | spi | |
| 14 | 19 | MISOKB_GPIO19PWM | safe | spi | |
| 15 | 21 | SDASDA0PWM | safe | i2c | |
| 16 | 22 | SCLSCL0PWM | safe | i2c | |
| 17 | 23 | MOSIPWM | safe | spi | |
| 18 | 25 | A18DAC1PWM | safe | adc · dac | |
| 19 | 26 | A19DAC2OUTPUT1PWM | safe | adc · dac | |
| 20 | 27 | A17T7OUTPUT2PWM | safe | adc · touch | |
| 21 | 32 | A4T9INPUT1PWM | safe | adc · touch | |
| 22 | 33 | A5T8INPUT2PWM | safe | adc · touch | |
| 23 | 34 | A6INPUT3 | strapping | adc | |
| 24 | 35 | A7INPUT4 | strapping | adc | |
| 25 | 36 | A0LDR_PIN | strapping | adc | |
| 26 | 39 | A3 | strapping | adc | |
| 27 | - | KB_GPIO23= | safe | - |
Start with these
13 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
13 pins · 12 things to knowA11GPIO0 Bootstrapping pin (enter bootloader when low); internal pull-up. Strapping
Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode.
TXGPIO1 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.
A12GPIO2 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.
SSGPIO5 Bootstrapping pin; internal pull-up; VSPI CS0 (default SPI chip-select); acts as FSPIWP (flash write-protect) on internal-flash variants. Strapping
Must be HIGH during boot; if pulled LOW at reset, alters SDIO slave timing and may prevent normal boot.
A15GPIO12 Bootstrapping pin; JTAG TDI; sets flash voltage (VDD_SDIO); also HSPIQ (flash data line). Strapping
Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used.
A14GPIO13 JTAG clock pin (TCK); also ADC2 channel 4 / Touch4 input. JTAG
Used for JTAG debugging (TCK); avoid using as GPIO if JTAG is needed.
A16GPIO14 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.
A13GPIO15 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.
A6GPIO34 Input-only GPIO (no output driver); ADC1 channel 6. Other
Cannot be used as output (no drive capability); only suitable for analog/digital input.
A7GPIO35A3GPIO39 Input-only GPIOs with ADC1 channels - no output driver Other
Cannot be used as output; only suitable for input.
- A7Input-only GPIO (no output driver); ADC1 channel 7.
- A3Input-only GPIO (no output); ADC1 channel 3, Hall sensor VN.
A0GPIO36 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).
The INEX OpenKB pinout brings out 27 pins - 26 usable GPIO.
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 16 ADC-capable pins for sensors and battery monitoring, 10 capacitive-touch inputs and 2 true DAC outputs.
13 of the exposed pins carry boot-time or system duties on the ESP32 (A11, TX, A12 and 10 more) - check the guidance above before wiring anything to them. A10, LED_BUILTIN, BT_LED, SCK and 9 more 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:OpenKB]
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 · vs other ESP32 chips →About this board
Inside sits the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
At $24.00 it's on the expensive side for an ESP32 board - most land around $20.
Around the module: an MCP79411 RTC, a buzzer, an environmental sensor (LM73), an ambient-light sensor, status LEDs (WiFi, Bluetooth, NTP, IoT status) and SW1/SW2 buttons.
- 16x8 red LED dot-matrix display
- Real-time clock backed by a supercapacitor keeps time ~90h without power
- KidBright IDE compatible via the OpenKB plugin (also Arduino, ESP-IDF, PlatformIO)
Where to buy
prices are typical street pricesResources
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