Advanced communication principles

Advanced communication principles describe how embedded devices exchange data reliably and efficiently beyond a simple wire.

1. Layering: communication is split into layers, each providing services to the one above. Typical layers: physical (wires, voltage, bit timing), data link (framing, error detection, medium access), network (addressing, routing), transport (end-to-end reliability) and application. Each layer can be changed independently.
2. Serial versus parallel communication: serial uses one data wire (fewer pins, longer distance, e.g. UART, SPI, I2C, USB, CAN); parallel uses many wires at once (faster per clock, but costly and prone to skew).
3. Synchronous and asynchronous transfer: synchronous uses a shared clock (SPI, I2C); asynchronous uses start/stop bits and an agreed baud rate (UART).
4. Error detection and correction: parity bit, checksum, CRC and Hamming codes detect or correct corrupted bits.
5. Multiple access / arbitration: several nodes sharing a medium use TDMA, FDMA, CDMA, CSMA/CD, or priority arbitration (CAN).
6. Wireless communication: infrared, Bluetooth, ZigBee, Wi-Fi and RFID; need modulation, addressing, security and power saving.
7. Flow control and handshaking: prevents a fast sender overflowing a slow receiver.
8. Protocols: agreed rules for formats and timing, e.g. I2C, CAN, USB, Ethernet, TCP/IP.