Along with the book evaluating standards for renewable energy building's application projects implements in our country, we are in urgent need of the operational datas about the renewable energy building's application demonstration projects. The data acquisition system of the renewable energy building's application demonstration projects has one demand of multiple serial ports and a 485 bus communication. This paper uses ARM9 S3C2440 embedded microcontroller and VK3234 with four channel UART/SPI interface to extend serial. What's more, it achieves the 485 communication between the field detection device and data acquisition device with MAX3485. This paper states the interface and software and hardware between S3C2440, VK3234 and MAX3485E specifically. The practical running test in the laboratory shows that the system is stable and reliable, and it has been applied in the data monitoring system of the renewable energy demonstration projects.