RTduino is an Arduino ecosystem compatibility layer for the RT-Thread real-time operating system. It enables developers to use Arduino programming functions, libraries, and methodologies directly within RT-Thread projects, significantly lowering the learning curve for RT-Thread and its supported chips. By bridging the two ecosystems, RTduino allows seamless integration of thousands of third-party Arduino libraries, including sensor drivers and algorithm libraries, enriching the RT-Thread software package ecosystem. It supports standard Arduino APIs such as digital and analog read/write, PWM, ADC, and serial, I2C, and SPI communication interfaces. RTduino is compatible with various RT-Thread BSPs, including Renesas RA6M3 HMI, NXP LPC55S69 EVK, STM32F407 Spark Explorer, Raspberry Pi Pico, and STM32F072 Nucleo, making it a versatile solution for embedded developers seeking to leverage Arduino's extensive library support on RT-Thread platforms.