Web-Based Data Acquistion System using a 32 bit Single Board Computer and GNU/LINUX

Abstract

Most of the previous research in Data Acquisition System (DAS) had used Personal Computers (PCs) as hardware platform which were bulky and not portable. In this research, a Portable Embedded Sensing System (PESS) has been developed using commercial off-the-shelf (COTS) embedded system. Current COTS technology provides more flexibility in term of portability, scalability and configurability. PESS is made-up of an integration of TS-5500 Single Board Computer (SBC) as its computing core, a matrix keypad, a LCD display and sensors that attached to the interfacing circuit. As for the software part, PESS uses the open source GNU/Linux that allows modification to its libraries and device drivers. PESS has been extended by enabling a TCP/IP network connection to a server in order to accommodate bigger data archiving. These two-nodes network-based system is called PESS-n which divided to PESS and PESS-Server. PESS-n is equipped with an error-correction mechanism that can minimize data loses in the event of network failures, in addition to sending the backup data. A user interface has been developed at PESS-Server side to allow the acquired data to be presented in graphical format as well sharing of data via Internet. On the analog acquisition, not more than three steps resolution for the average bit of error has consistently been achieved. As for the network data transfer performance, both Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) have been evaluated. While UDP provide faster recovery times during simulated network failures, it has limitation up to 64 KB of data payload only. As for the TCP, it has been able to transmit large data up to 1.6 MB which equal to fourteen days of data. It is found that the data losses of TCP and UDP are very small (2-3 unit of data).