A hardware based digital communication system that demonstrates how data can be encoded, transmitted, and checked for errors using non zero encoding, parity checking, and Cyclic Redundancy Check (CRC).
this project was built as a practical exploration of digital communication and error detection using discrete logic and hardware rather than relying entirely on software. The system takes digital data, processes it through different stages of encoding and error detection, transmits it through a physical connection, and allows the receiver to verify the integrity of the received data.
Digital systems constantly move data from one place to another. Whether the data is traveling between two ICs on a circuit board, between computers over a network, or across a communication link, there is always a possibility that some bits may be altered during transmission.
A transmitted: 10110101
could potentially arrive as: 10100101
Even a single flipped bit can change the meaning of the entire message.
This project demonstrates how a communication system can detect such errors.
The general process is:
DATA --> Non-Zero Encode --> Error Detection Calculation: CRC --> Transmitter --> digital transmission --> Error Checking --> VALID DATA
The hardware implementation makes it possible to observe these operations directly rather than treating them as abstract software calculations.
A short demonstration of the system transmitting data is shown below.
demo.mp4
The video is intentionally short and focuses on the actual transmission process rather than recording the entire operation.
The main purpose of this project is to demonstrate that the receiver should not blindly trust the data it receives.
Instead, additional information can be transmitted along with the original data. The receiver can then use that information to determine whether the data was corrupted.
Two of the main techniques demonstrated in this project are:
- Parity checking
- Cyclic Redundancy Check (CRC)
The project also uses non zero encoding as part of the data transmission process.
Before transmitting the data, the signal is encoded so that the transmission does not remain at a constant zero level for long periods.a long sequence of zeros can make it difficult to distinguish between an actual data signal and the absence of a signal. Non zero encoding helps ensure that there are meaningful transitions in the transmitted signal. The basic idea is to transform the original data into a form that is more suitable for physical transmission.
The image above shows the encoding calculations used in the project. This stage is important because error detection is only useful if the underlying data can be transmitted reliably in the first place.
The basic idea is to add an additional bit to a group of data bits. This extra bit is chosen according to the number of 1s present in the original data.
For example, consider: Data: 1011001
The number of 1s can be counted and a parity bit can be generated accordingly.
Depending on the chosen parity scheme, the transmitted data may look like: 1011001 + parity bit
When the receiver gets the data, it performs the same calculation. If the expected parity does not match the received parity, the receiver knows that the data has been corrupted.
The calculation above shows how the parity value is generated from the transmitted data.
CRC is a much more powerful error detection technique than a simple parity bit. Instead of simply counting the number of 1s, CRC treats the data as a binary polynomial and performs polynomial division using a predefined generator polynomial. The remainder of this division becomes the CRC value.
The general process is:
Original Data --> Append zeros --> Polynomial Division --> CRC Remainder --> Transmit Data + CRC
At the receiver, the same generator polynomial is used to check the received message. If the resulting remainder is not what is expected, the receiver knows that an error occurred during transmission.
The transmitter is responsible for preparing the data before it is sent to the receiver.
The general flow is:
Input Data --> Encoding --> Error Detection Information --> Transmission Logic --> Output Signal
The receiver takes the transmitted signal and reconstructs the digital data. After receiving the data, it can perform the required checks to determine whether the transmission was successful.
The general process is:
Received Signal --> Data Recovery --> Error Detection
│
├─ Valid --> Data Accepted
│
└── Error --> Data Rejected
