This project is my first attempt at learning how to interface different sensors using I2C protocol, SPI protocol, Analog protocol, and adding a communication module (Lilypad)    

I²C is a multi-master protocol that uses 2 signal lines. The two I²C signals are called ‘serial data’ (SDA) and ‘serial clock’ (SCL). There is no need of chip select (slave select) or arbitration logic. Virtually any number of slaves and any number of masters can be connected onto these 2 signal lines and communicate between each other using a protocol that defines:

– 7-bits slave addresses: each device connected to the bus has got such a unique address;
– data divided into 8-bit bytes
– a few control bits for controlling the communication start, end, direction and for an acknowledgment mechanism.


SPI is quite straightforward – it defines features any digital electronic engineer would think of if it were to quickly define a way to communicate between 2 digital devices. SPI is a protocol on 4 signal lines (please refer to figure 1):

– A clock signal named SCLK, sent from the bus master to all slaves; all the SPI signals are synchronous to this clock signal;
– A slave select signal for each slave, SSn, used to select the slave the master communicates with;
– A data line from the master to the slaves, named MOSI (Master Out-Slave In)
– A data line from the slaves to the master, named MISO (Master In-Slave Out).


This project can be used for atmosheric monitoring and could be integrated to make it a wearable project.