Serial Communication Protocols

Overview

• Importance: Efficient transfer of digital data with fewer connections.
• Popular Protocols: Particularly for microcontrollers like PIC and Arduino.
• Focus: UART, I²C, and SPI protocols.
• Tools: Arduino and oscilloscope for demonstrations.

Serial Communication Protocol

• Concept: Transmit data in a sequence, bit by bit, using a single data line.
• Alternative - Parallel Communication:
  • Transmits multiple data bits simultaneously on separate lines.
  • Downside: Requires many connections (e.g., 8-bits require 9 cables).
• Serial Communication:
  • Sends data bits sequentially on a single line.
  • Disadvantage: Slower since one clock pulse per bit is needed.
• Examples: UART, I²C, SPI, USB, etc.

Synchronous vs Asynchronous

• Asynchronous: No clock; relies on agreed-upon speed and start/stop bits.
• Synchronous: Uses a clock signal to synchronize data transfer.

UART (Universal Asynchronous Receiver Transmitter)

• Basics: Uses one data line (TX) and one receiver line (RX), plus ground.
• Start/Stop Bits: Defines the start and end of data frames.
• Transmission Speed: Commonly 9600 baud (bits per second).
• Communication Process:
  • Start bit signals the beginning of data.
  • Data bits are followed by a stop bit.
• Example: Arduino uses UART for uploading code and serial monitor communication.
• Additional Pins: DTR and CTS for flow control.
• Visualization: Data representation on oscilloscope matches start/data/stop bit structure.

I²C (Inter-Integrated Circuit)

• Basics: Developed by Philips; requires 2 lines (SDA for data, SCL for clock) plus ground.
• Speed: Up to 400 kbps.
• Addressing: Uses slave addresses to communicate with multiple devices.
• Use Cases: Good for one-to-many communication.
• Visualization: Oscilloscope shows clock and data signals, including slave address.

SPI (Serial Peripheral Interface)

• Basics:
  • Requires 5 connections: Clock, MOSI, MISO, chip select (CS), and ground.
  • Full-duplex: Can send and receive data simultaneously.
• Speed: Faster than UART and I²C, with lower power consumption.
• Range: Limited to short distances; lacks acknowledgment pins like DTR or CTS.
• Use Cases: Ideal for high-speed and full-duplex communication.
• Visualization: Oscilloscope shows clock, data (MOSI, MISO), and chip select signals.

Comparative Summary

• UART: Simple, asynchronous, good for short-range and low-speed communication.
• I²C: Synchronous, suitable for one-to-many communication with moderate speed.
• SPI: Synchronous, high-speed, full-duplex, limited to short distances.

Conclusion

• Common Uses: Arduino supports all three protocols.
• Future Topics: Possible exploration of other protocols like JTAG, CAN, USB.
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