17-09-2009, 02:06 AM
PC Based data acquisition system by stimulating SPI and I2C protocol
Many times it is required to monitor physical phenomena such as temperature, pressure humidity, light intensity, sound intensity, force, etc. Such physical phenomena can be monitored by digital systems employing sensors. However sensor generally produces a change in the resistance, voltage or current. All such phenomena can be converted in to a change in voltage levels. Since the sensors and the subsequent signal conditioning circuits provide a proportionate change in voltage with respective the phenomena, this cannot be directly interpreted by a digital system. A sensor is ussaually an analog voltage and can take any value between +10 to -10 volts. However a digital system has only two states (ON) or (OFF). Thus it is required to have additional circuitry between the digital systems and analog systems that translate the analog signals in to a digital signals. Such conversion can be perform by an analog to digital converter.
The Serial Peripheral interface Bus or SPI (often pronounced spy) bus Is a synchronous serial data page link standard that operates in full duplex mode. Devices communicate in master/slave mode where the master device initiates the data frame. Multiple slave devices are allowed with individual slave select (chip select) lines. The I2C bus physically consists of two active wires and a ground connection. The active wires called SDA and SCL, are both bi-directional. SDA is a serial data line, SCL is a serial clock line.
Data Acquisition refers to reading the data continuously from any sensor. Here we are continuously monitoring the data through PC. We are concentrating mostly on serial communication. The data which we are receiving from the sensor is received by the micro controller using ADC. We need to monitor this data on the PC and on the LCD, In order to send the data we are using serial communication. We get the information like Date and Time with our data. The buzzer rings when the temperature reaches a critical temperature of 35degrees centigrade.
The data that is stored in PC is easier to monitor are retrieve at any time compared to storing in a particular memory. Now a days we are using the same process as storing the data in the PC in any kind of industr
