Popular open source small Microcontroller board
You can learn Arduino in 15 minutes.
You can go to the Online cloud based or download the IDE from Arduino software by clicking here
Basic Specification
ATmega328 processor 16 MHz
2k RAM
Flash Memory 32 KB (0.5 KB is used for Bootloader)
Input Voltage Limits 6-20V (Recommended 7-12V)
Analog Input Pins 6 (A0 – A5)
Digital I/O Pins 14 (Out of which 6 provide PWM output)
DC Current on I/O Pins 40 mA
Many interface boards and shields
Cheap alternatives worth a look
MSP430 LaunchPad (The Value Line LaunchPad $4.30 ) 512b RAM
STM32 Discovery from STMicroelectronics $9.88 32-bit ARM Cortex M3 24 MHz with 8 kB of RAM
Teensy 2.0 $20 and its counterpart, Teensy++ 2.0 $27.50, 16 MHz AVR processor
Arduino Bluno Beetle BLE, low cost Arduino with bluetooth 4.0
Using Rotary Encoders with Arduino
OTHER Arduino versions
I recommend you jump right to a STM32 Arduino (or the faster GD32) or ESP32S
A comparison of many common Arduino types and their uses.
STM32
STM32 Arduino Tutorial
Easy & Powerful Arduino Alternative? STM32 Beginner's Guide
TOP 20 Arduino Projects
Adding Buttons with Button2